![sting of a hornet and almost exactly like the sting of a scorpion-fish.
Most of the Nematognathi possess a fleshy or adipose fin behind the
dorsal, exactly as in the salmon. In a few cases the adipose fin
develops an anterior spine and occasionally supporting rays.
All the Nematognathi are carnivorous bottom feeders, devouring any
prey they can swallow. Only a few enter the sea, and they occur in
the greatest abundance in the Amazon region. Upward of 1200
species, arranged in 150 genera, are recorded. They vary greatly in
size, from two inches to six feet in length. All are regarded as food-
fishes, but the species in the sea have very tough and flavorless
flesh. Some of the others are extremely delicate, with finely flavored
flesh and a grateful absence of small bones.
Families of Nematognathi.—According to Dr. Eigenmann's
scheme of classification,[11]
the most primitive family of
Nematognathi is that of Diplomystidæ, characterized by the
presence of a well-developed maxillary, as in other soft-rayed fishes.
The single species, Diplomystes papillosus, is found in the waters of
Chile.
11. A Revision of the South American Nematognathi, 1890, p. 7.
Similar to the Diplomystidæ in all other respects is the great central
family of Siluridæ, by far the most numerous and important of all the
divisions of Nematognathi.
The Siluridæ.—This group has the skin naked or imperfectly
mailed, the barbels on the head well developed, the dorsal short,
inserted forward, the adipose fin without spine, and the lower
pharyngeals separate. All the marine catfishes and most of the
fresh-water species belong to this group, and its members, some
700 species, abound in all parts of the world where catfishes are
known—"a bloodthirsty and bullying race of rangers inhabiting the
river bottoms with ever a lance at rest and ready to do battle with
their nearest neighbor."
The Sea Catfish.—In the tropical seas are numerous species of
catfishes belonging to Tachysurus, Arius, Galeichthys, Felichthys, and](https://image.slidesharecdn.com/14193-250620102801-38c2708c/85/Scala-Applied-Machine-Learning-1st-Edition-Pascal-Bugnion-38-320.jpg)
Scala Applied Machine Learning 1st Edition Pascal Bugnion
- 1. Scala Applied Machine Learning 1st Edition Pascal Bugnion download https://textbookfull.com/product/scala-applied-machine- learning-1st-edition-pascal-bugnion/ Download full version ebook from https://textbookfull.com
- 2. We believe these products will be a great fit for you. Click the link to download now, or visit textbookfull.com to discover even more! Scala Guide for Data Science Professionals 1st Edition Pascal Bugnion https://textbookfull.com/product/scala-guide-for-data-science- professionals-1st-edition-pascal-bugnion/ Applied Machine Learning 1st Edition M. Gopal https://textbookfull.com/product/applied-machine-learning-1st- edition-m-gopal/ Learning Concurrent Programming in Scala Prokopec https://textbookfull.com/product/learning-concurrent-programming- in-scala-prokopec/ Applied Machine Learning for Health and Fitness: A Practical Guide to Machine Learning with Deep Vision, Sensors and IoT Kevin Ashley https://textbookfull.com/product/applied-machine-learning-for- health-and-fitness-a-practical-guide-to-machine-learning-with- deep-vision-sensors-and-iot-kevin-ashley/
- 3. Hands On Unsupervised Learning Using Python How to Build Applied Machine Learning Solutions from Unlabeled Data 1st Edition Ankur A. Patel https://textbookfull.com/product/hands-on-unsupervised-learning- using-python-how-to-build-applied-machine-learning-solutions- from-unlabeled-data-1st-edition-ankur-a-patel/ Applied Text Analysis with Python Enabling Language Aware Data Products with Machine Learning 1st Edition Benjamin Bengfort https://textbookfull.com/product/applied-text-analysis-with- python-enabling-language-aware-data-products-with-machine- learning-1st-edition-benjamin-bengfort/ Scala and Spark for Big Data Analytics Explore the concepts of functional programming data streaming and machine learning 1st Edition Md. Rezaul Karim https://textbookfull.com/product/scala-and-spark-for-big-data- analytics-explore-the-concepts-of-functional-programming-data- streaming-and-machine-learning-1st-edition-md-rezaul-karim/ Applied Natural Language Processing with Python: Implementing Machine Learning and Deep Learning Algorithms for Natural Language Processing 1st Edition Taweh Beysolow Ii https://textbookfull.com/product/applied-natural-language- processing-with-python-implementing-machine-learning-and-deep- learning-algorithms-for-natural-language-processing-1st-edition- taweh-beysolow-ii/ Python Real World Machine Learning: Real World Machine Learning: Take your Python Machine learning skills to the next level 1st Edition Joshi https://textbookfull.com/product/python-real-world-machine- learning-real-world-machine-learning-take-your-python-machine- learning-skills-to-the-next-level-1st-edition-joshi/
- 6. Table of Contents Scala:Applied Machine Learning Scala:Applied Machine Learning Credits Preface What this learning path covers What you need for this learning path Module 1 Installing the JDK Installing and using SBT Module 2 Module 3 Who this learning path is for Reader feedback Customer support Downloading the example code Errata Piracy Questions I. Module 1 1. Scala and Data Science Data science Programming in data science Why Scala? Static typing and type inference Scala encourages immutability Scala and functional programs Null pointer uncertainty Easier parallelism Interoperability with Java When not to use Scala Summary References
- 7. 2. Manipulating Data with Breeze Code examples Installing Breeze Getting help on Breeze Basic Breeze data types Vectors Dense and sparse vectors and the vector trait Matrices Building vectors and matrices Advanced indexing and slicing Mutating vectors and matrices Matrix multiplication, transposition, and the orientation of vectors Data preprocessing and feature engineering Breeze – function optimization Numerical derivatives Regularization An example – logistic regression Towards re-usable code Alternatives to Breeze Summary References 3. Plotting with breeze-viz Diving into Breeze Customizing plots Customizing the line type More advanced scatter plots Multi-plot example – scatterplot matrix plots Managing without documentation Breeze-viz reference Data visualization beyond breeze-viz Summary 4. Parallel Collections and Futures Parallel collections Limitations of parallel collections Error handling
- 8. Setting the parallelism level An example – cross-validation with parallel collections Futures Future composition – using a future's result Blocking until completion Controlling parallel execution with execution contexts Futures example – stock price fetcher Summary References 5. Scala and SQL through JDBC Interacting with JDBC First steps with JDBC Connecting to a database server Creating tables Inserting data Reading data JDBC summary Functional wrappers for JDBC Safer JDBC connections with the loan pattern Enriching JDBC statements with the "pimp my library" pattern Wrapping result sets in a stream Looser coupling with type classes Type classes Coding against type classes When to use type classes Benefits of type classes Creating a data access layer Summary References 6. Slick – A Functional Interface for SQL FEC data Importing Slick Defining the schema Connecting to the database Creating tables Inserting data
- 9. Querying data Invokers Operations on columns Aggregations with "Group by" Accessing database metadata Slick versus JDBC Summary References 7. Web APIs A whirlwind tour of JSON Querying web APIs JSON in Scala – an exercise in pattern matching JSON4S types Extracting fields using XPath Extraction using case classes Concurrency and exception handling with futures Authentication – adding HTTP headers HTTP – a whirlwind overview Adding headers to HTTP requests in Scala Summary References 8. Scala and MongoDB MongoDB Connecting to MongoDB with Casbah Connecting with authentication Inserting documents Extracting objects from the database Complex queries Casbah query DSL Custom type serialization Beyond Casbah Summary References 9. Concurrency with Akka GitHub follower graph Actors as people
- 10. Hello world with Akka Case classes as messages Actor construction Anatomy of an actor Follower network crawler Fetcher actors Routing Message passing between actors Queue control and the pull pattern Accessing the sender of a message Stateful actors Follower network crawler Fault tolerance Custom supervisor strategies Life-cycle hooks What we have not talked about Summary References 10. Distributed Batch Processing with Spark Installing Spark Acquiring the example data Resilient distributed datasets RDDs are immutable RDDs are lazy RDDs know their lineage RDDs are resilient RDDs are distributed Transformations and actions on RDDs Persisting RDDs Key-value RDDs Double RDDs Building and running standalone programs Running Spark applications locally Reducing logging output and Spark configuration Running Spark applications on EC2 Spam filtering
- 11. Lifting the hood Data shuffling and partitions Summary Reference 11. Spark SQL and DataFrames DataFrames – a whirlwind introduction Aggregation operations Joining DataFrames together Custom functions on DataFrames DataFrame immutability and persistence SQL statements on DataFrames Complex data types – arrays, maps, and structs Structs Arrays Maps Interacting with data sources JSON files Parquet files Standalone programs Summary References 12. Distributed Machine Learning with MLlib Introducing MLlib – Spam classification Pipeline components Transformers Estimators Evaluation Regularization in logistic regression Cross-validation and model selection Beyond logistic regression Summary References 13. Web APIs with Play Client-server applications Introduction to web frameworks Model-View-Controller architecture
- 12. Single page applications Building an application The Play framework Dynamic routing Actions Composing the response Understanding and parsing the request Interacting with JSON Querying external APIs and consuming JSON Calling external web services Parsing JSON Asynchronous actions Creating APIs with Play: a summary Rest APIs: best practice Summary References 14. Visualization with D3 and the Play Framework GitHub user data Do I need a backend? JavaScript dependencies through web-jars Towards a web application: HTML templates Modular JavaScript through RequireJS Bootstrapping the applications Client-side program architecture Designing the model The event bus AJAX calls through JQuery Response views Drawing plots with NVD3 Summary References A. Pattern Matching and Extractors Pattern matching in for comprehensions Pattern matching internals Extracting sequences Summary
- 13. Reference II. Module 2 1. Getting Started Mathematical notation for the curious Why machine learning? Classification Prediction Optimization Regression Why Scala? Abstraction Higher-kind projection Covariant functors for vectors Contravariant functors for co-vectors Monads Scalability Configurability Maintainability Computation on demand Model categorization Taxonomy of machine learning algorithms Unsupervised learning Clustering Dimension reduction Supervised learning Generative models Discriminative models Semi-supervised learning Reinforcement learning Don't reinvent the wheel! Tools and frameworks Java Scala Apache Commons Math Description Licensing
- 14. Installation JFreeChart Description Licensing Installation Other libraries and frameworks Source code Context versus view bounds Presentation Primitives and implicits Primitive types Type conversions Immutability Performance of Scala iterators Let's kick the tires An overview of computational workflows Writing a simple workflow Step 1 – scoping the problem Step 2 – loading data Step 3 – preprocessing the data Immutable normalization Step 4 – discovering patterns Analyzing data Plotting data Step 5 – implementing the classifier Selecting an optimizer Training the model Classifying observations Step 6 – evaluating the model Summary 2. Hello World! Modeling A model by any other name Model versus design Selecting features Extracting features
- 15. Defining a methodology Monadic data transformation Error handling Explicit models Implicit models A workflow computational model Supporting mathematical abstractions Step 1 – variable declaration Step 2 – model definition Step 3 – instantiation Composing mixins to build a workflow Understanding the problem Defining modules Instantiating the workflow Modularization Profiling data Immutable statistics Z-Score and Gauss Assessing a model Validation Key quality metrics F-score for binomial classification F-score for multinomial classification Cross-validation One-fold cross validation K-fold cross validation Bias-variance decomposition Overfitting Summary 3. Data Preprocessing Time series in Scala Types and operations The magnet pattern The transpose operator The differential operator Lazy views
- 16. Moving averages The simple moving average The weighted moving average The exponential moving average Fourier analysis Discrete Fourier transform DFT-based filtering Detection of market cycles The discrete Kalman filter The state space estimation The transition equation The measurement equation The recursive algorithm Prediction Correction Kalman smoothing Fixed lag smoothing Experimentation Benefits and drawbacks Alternative preprocessing techniques Summary 4. Unsupervised Learning Clustering K-means clustering Measuring similarity Defining the algorithm Step 1 – cluster configuration Defining clusters Initializing clusters Step 2 – cluster assignment Step 3 – reconstruction/error minimization Creating K-means components Tail recursive implementation Iterative implementation Step 4 – classification The curse of dimensionality
- 17. Setting up the evaluation Evaluating the results Tuning the number of clusters Validation The expectation-maximization algorithm Gaussian mixture models Overview of EM Implementation Classification Testing The online EM algorithm Dimension reduction Principal components analysis Algorithm Implementation Test case Evaluation Non-linear models Kernel PCA Manifolds Performance considerations K-means EM PCA Summary 5. Naïve Bayes Classifiers Probabilistic graphical models Naïve Bayes classifiers Introducing the multinomial Naïve Bayes Formalism The frequentist perspective The predictive model The zero-frequency problem Implementation Design Training
- 18. Class likelihood Binomial model The multinomial model Classifier components Classification F1 validation Feature extraction Testing The Multivariate Bernoulli classification Model Implementation Naïve Bayes and text mining Basics of information retrieval Implementation Analyzing documents Extracting the frequency of relative terms Generating the features Testing Retrieving the textual information Evaluating the text mining classifier Pros and cons Summary 6. Regression and Regularization Linear regression One-variate linear regression Implementation Test case Ordinary least squares regression Design Implementation Test case 1 – trending Test case 2 – feature selection Regularization Ln roughness penalty Ridge regression Design
- 19. Implementation Test case Numerical optimization Logistic regression Logistic function Binomial classification Design The training workflow Step 1 – configuring the optimizer Step 2 – computing the Jacobian matrix Step 3 – managing the convergence of the optimizer Step 4 – defining the least squares problem Step 5 – minimizing the sum of square errors Test Classification Summary 7. Sequential Data Models Markov decision processes The Markov property The first order discrete Markov chain The hidden Markov model Notations The lambda model Design Evaluation – CF-1 Alpha – the forward pass Beta – the backward pass Training – CF-2 The Baum-Welch estimator (EM) Decoding – CF-3 The Viterbi algorithm Putting it all together Test case 1 – training Test case 2 – evaluation HMM as a filtering technique Conditional random fields
- 20. Introduction to CRF Linear chain CRF Regularized CRFs and text analytics The feature functions model Design Implementation Configuring the CRF classifier Training the CRF model Applying the CRF model Tests The training convergence profile Impact of the size of the training set Impact of the L2 regularization factor Comparing CRF and HMM Performance consideration Summary 8. Kernel Models and Support Vector Machines Kernel functions An overview Common discriminative kernels Kernel monadic composition Support vector machines The linear SVM The separable case – the hard margin The nonseparable case – the soft margin The nonlinear SVM Max-margin classification The kernel trick Support vector classifiers – SVC The binary SVC LIBSVM Design Configuration parameters The SVM formulation The SVM kernel function The SVM execution
- 21. Interface to LIBSVM Training Classification C-penalty and margin Kernel evaluation Applications in risk analysis Anomaly detection with one-class SVC Support vector regression An overview SVR versus linear regression Performance considerations Summary 9. Artificial Neural Networks Feed-forward neural networks The biological background Mathematical background The multilayer perceptron The activation function The network topology Design Configuration Network components The network topology Input and hidden layers The output layer Synapses Connections The initialization weights The model Problem types (modes) Online training versus batch training The training epoch Step 1 – input forward propagation The computational flow Error functions Operating modes
- 22. Softmax Step 2 – error backpropagation Weights' adjustment The error propagation The computational model Step 3 – exit condition Putting it all together Training and classification Regularization The model generation The Fast Fisher-Yates shuffle Prediction Model fitness Evaluation The execution profile Impact of the learning rate The impact of the momentum factor The impact of the number of hidden layers Test case Implementation Evaluation of models Impact of the hidden layers' architecture Convolution neural networks Local receptive fields Sharing of weights Convolution layers Subsampling layers Putting it all together Benefits and limitations Summary 10. Genetic Algorithms Evolution The origin NP problems Evolutionary computing Genetic algorithms and machine learning
- 23. Genetic algorithm components Encoding Value encoding Predicate encoding Solution encoding The encoding scheme Flat encoding Hierarchical encoding Genetic operators Selection Crossover Mutation The fitness score Implementation Software design Key components Population Chromosomes Genes Selection Controlling the population growth The GA configuration Crossover Population Chromosomes Genes Mutation Population Chromosomes Genes Reproduction Solver GA for trading strategies Definition of trading strategies Trading operators The cost function
- 24. Trading signals Trading strategies Trading signal encoding A test case Creating trading strategies Configuring the optimizer Finding the best trading strategy Tests The weighted score The unweighted score Advantages and risks of genetic algorithms Summary 11. Reinforcement Learning Reinforcement learning The problem A solution – Q-learning Terminology Concepts Value of a policy The Bellman optimality equations Temporal difference for model-free learning Action-value iterative update Implementation Software design The states and actions The search space The policy and action-value The Q-learning components The Q-learning training Tail recursion to the rescue The validation The prediction Option trading using Q-learning The OptionProperty class The OptionModel class Quantization
- 25. Putting it all together Evaluation Pros and cons of reinforcement learning Learning classifier systems Introduction to LCS Why LCS? Terminology Extended learning classifier systems XCS components Application to portfolio management The XCS core data XCS rules Covering An implementation example Benefits and limitations of learning classifier systems Summary 12. Scalable Frameworks An overview Scala Object creation Streams Parallel collections Processing a parallel collection The benchmark framework Performance evaluation Scalability with Actors The Actor model Partitioning Beyond actors – reactive programming Akka Master-workers Exchange of messages Worker actors The workflow controller The master actor Master with routing
- 26. Distributed discrete Fourier transform Limitations Futures The Actor life cycle Blocking on futures Handling future callbacks Putting it all together Apache Spark Why Spark? Design principles In-memory persistency Laziness Transforms and actions Shared variables Experimenting with Spark Deploying Spark Using Spark shell MLlib RDD generation K-means using Spark Performance evaluation Tuning parameters Tests Performance considerations Pros and cons 0xdata Sparkling Water Summary A. Basic Concepts Scala programming List of libraries and tools Code snippets format Best practices Encapsulation Class constructor template Companion objects versus case classes Enumerations versus case classes
- 27. Overloading Design template for immutable classifiers Utility classes Data extraction Data sources Extraction of documents DMatrix class Counter Monitor Mathematics Linear algebra QR decomposition LU factorization LDL decomposition Cholesky factorization Singular Value Decomposition Eigenvalue decomposition Algebraic and numerical libraries First order predicate logic Jacobian and Hessian matrices Summary of optimization techniques Gradient descent methods Steepest descent Conjugate gradient Stochastic gradient descent Quasi-Newton algorithms BFGS L-BFGS Nonlinear least squares minimization Gauss-Newton Levenberg-Marquardt Lagrange multipliers Overview of dynamic programming Finances 101 Fundamental analysis Technical analysis
- 28. Terminology Trading data Trading signals and strategy Price patterns Options trading Financial data sources Suggested online courses References III. Module 3 1. Exploratory Data Analysis Getting started with Scala Distinct values of a categorical field Summarization of a numeric field Grepping across multiple fields Basic, stratified, and consistent sampling Working with Scala and Spark Notebooks Basic correlations Summary 2. Data Pipelines and Modeling Influence diagrams Sequential trials and dealing with risk Exploration and exploitation Unknown unknowns Basic components of a data-driven system Data ingest Data transformation layer Data analytics and machine learning UI component Actions engine Correlation engine Monitoring Optimization and interactivity Feedback loops Summary 3. Working with Spark and MLlib Setting up Spark
- 29. Understanding Spark architecture Task scheduling Spark components MQTT, ZeroMQ, Flume, and Kafka HDFS, Cassandra, S3, and Tachyon Mesos, YARN, and Standalone Applications Word count Streaming word count Spark SQL and DataFrame ML libraries SparkR Graph algorithms – GraphX and GraphFrames Spark performance tuning Running Hadoop HDFS Summary 4. Supervised and Unsupervised Learning Records and supervised learning Iris dataset Labeled point SVMWithSGD Logistic regression Decision tree Bagging and boosting – ensemble learning methods Unsupervised learning Problem dimensionality Summary 5. Regression and Classification What regression stands for? Continuous space and metrics Linear regression Logistic regression Regularization Multivariate regression Heteroscedasticity Regression trees
- 30. Another Random Scribd Document with Unrelated Content
- 31. Fig. 135.—Buffalo-fish, Ictiobus cyprinella (Cuv. & Val.). Normal, Ill. Fig. 136.—Carp-sucker, Carpiodes cyprinus (Le Sueur). Havre de Grace. The buffalo-fishes and carp-suckers, constituting the genera Ictiobus and Carpiodes, are the largest of the Catostomidæ, and bear a considerable resemblance to the carp. They have the dorsal fin many
- 32. rayed and the scales large and coarse. They abound in the large rivers and lakes between the Rocky Mountains and the Alleghanies, one species being found in Central America and a species of a closely related genus (Myxocyprinus asiaticus) being reported from eastern Asia. They rarely ascend the smaller rivers except for the purpose of spawning. Although so abundant in the Mississippi Valley as to be of importance commercially, they are very inferior as food- fishes, being coarse and bony. The genus Cycleptus contains the black-horse, or Missouri sucker, a peculiar species with a small head, elongate body, and jet-black coloration, which comes up the smaller rivers tributary to the Mississippi and Ohio in large numbers in the spring. Most of the other suckers belong to the genera Catostomus and Moxostoma, the latter with the large-toothed Placopharynx being known, from the red color of the fins, as red-horse, the former as sucker. Some of the species are very widely distributed, two of them (Catostomus commersoni, Erimyzon sucetta) being found in almost every stream east of the Rocky Mountains and Catostomus catostomus throughout Canada to the Arctic Sea. The most peculiar of the suckers in appearance is the harelip sucker (Quassilabia lacera) of the Western rivers. Very singular in form is the humpback or razor-back sucker of the Colorado, Xyrauchen cypho. Fig. 137.—Common Sucker, Catostomus commersoni (Le Sueur). Ecorse, Mich.
- 33. Fig. 138.—California Sucker, Catostomus occidentalis Agassiz. (Photograph by Cloudsley Rutter.) Fossil Cyprinidæ.—Fossil Cyprinidæ, closely related to existing forms, are found in abundance in fresh-water deposits of the Tertiary, but rarely if ever earlier than the Miocene. Cyprinus priscus occurs in the Miocene of Germany, perhaps showing that Germany was the original home of the so-called "German carp," afterwards actually imported to Germany from China. Some specimens referred to Barbus, Tinca, Rhodeus, Aspius, and Gobio are found in regions now inhabited by these genera, and many species are referred to the great genus Leuciscus, Leuciscus œningensis from the Miocene of Germany being perhaps the best known. Several species of Leuciscus or related genera are found in the Rocky Mountain region. Among these is the recently described Leuciscus turneri. Fossil Catostomidæ are very few and chiefly referred to the genus Amyzon, supposed to be allied to Erimyzon, but with a longer dorsal. Amyzon commune and other species are found in the Rocky Mountains, especially in the Miocene of the South Park in Colorado and the Eocene of Wyoming. Two or three species of Catostomus, known by their skulls, are found in the Pliocene of Idaho.
- 34. Fig. 139.—Pharyngeal teeth of Oregon Sucker, Catostomus macrocheilus.
- 35. Fig. 140.—Razor-back Sucker, Xyrauchen cypho (Lockington). Green River, Utah. The Loaches.—The Cobitidæ, or loaches, are small fishes, all less than a foot in length, inhabiting streams and ponds of Europe and Asia. In structure they are not very different from minnows, but they are rather eel-like in form, and the numerous long barbels about the mouth strongly suggest affinity with the catfishes. The scales are small, the pharyngeal teeth few, and the air-bladder, as in most small catfishes, enclosed in a capsule. The loaches are all bottom fishes of dark colors, tenacious of life, feeding on insects and worms. The species often bury themselves in mud and sand. They lie quiet on the bottom and move very quickly when disturbed much after the manner of darters and gobies. Species of Cobitis and Misgurnus are widely distributed from England to Japan. Nemachilus barbatulus is the commonest European species. Cobitis tænia is found, almost unchanged, from England to the streams of Japan. Remains of fossil loaches, mostly indistinguishable from Cobitis, occur in the Miocene and more recent rocks. From ancestors of loaches or other degraded Cyprinidæ we may trace the descent of the catfishes. The Homalopteridæ are small loaches in the mountain streams of the East Indies. They have no air-bladder and the number of
- 36. pharyngeal teeth (10 to 16) is greater than in the loaches, carp, or minnows.
- 37. CHAPTER IX THE NEMATOGNATHI, OR CATFISHES he Nematognathi.—The Nematognathi (νῆμα, thread; γνάθος, jaw), known collectively as catfishes, are recognized at once by the fact that the rudimentary and usually toothless maxillary is developed as the bony base of a long barbel or feeler. Usually other feelers are found around the head, suggesting the "smellers" of a cat. The body is never scaly, being either naked and smooth or else more or less completely mailed with bony plates which often resemble superficially those of a sturgeon. Other distinctive characters are found in the skeleton, notably the absence of the subopercle, but the peculiar development of the maxillary and its barbel with the absence of scales is always distinctive. The symplectic is usually absent, and in some the air-bladder is reduced to a rudiment inclosed in a bony capsule. In almost all cases a stout spine exists in the front of the dorsal fin and in the front of each pectoral fin. This spine, made of modified or coalescent soft rays, is often a strong weapon with serrated edges and capable of inflicting a severe wound. When the fish is alarmed, it sets this spine by a rotary motion in its socket joint. It can then be depressed only by breaking it. By a rotary motion upward and toward the body the spine is again lowered. The wounds made by this spine are often painful, but this fact is due not to a specific poison but to the irregular cut and to the slime of the spine. In two genera, Noturus and Schilbeodes, a poison-gland exists at the base of the pectoral spine, and the wound gives a sharp pain like the
- 38. sting of a hornet and almost exactly like the sting of a scorpion-fish. Most of the Nematognathi possess a fleshy or adipose fin behind the dorsal, exactly as in the salmon. In a few cases the adipose fin develops an anterior spine and occasionally supporting rays. All the Nematognathi are carnivorous bottom feeders, devouring any prey they can swallow. Only a few enter the sea, and they occur in the greatest abundance in the Amazon region. Upward of 1200 species, arranged in 150 genera, are recorded. They vary greatly in size, from two inches to six feet in length. All are regarded as food- fishes, but the species in the sea have very tough and flavorless flesh. Some of the others are extremely delicate, with finely flavored flesh and a grateful absence of small bones. Families of Nematognathi.—According to Dr. Eigenmann's scheme of classification,[11] the most primitive family of Nematognathi is that of Diplomystidæ, characterized by the presence of a well-developed maxillary, as in other soft-rayed fishes. The single species, Diplomystes papillosus, is found in the waters of Chile. 11. A Revision of the South American Nematognathi, 1890, p. 7. Similar to the Diplomystidæ in all other respects is the great central family of Siluridæ, by far the most numerous and important of all the divisions of Nematognathi. The Siluridæ.—This group has the skin naked or imperfectly mailed, the barbels on the head well developed, the dorsal short, inserted forward, the adipose fin without spine, and the lower pharyngeals separate. All the marine catfishes and most of the fresh-water species belong to this group, and its members, some 700 species, abound in all parts of the world where catfishes are known—"a bloodthirsty and bullying race of rangers inhabiting the river bottoms with ever a lance at rest and ready to do battle with their nearest neighbor." The Sea Catfish.—In the tropical seas are numerous species of catfishes belonging to Tachysurus, Arius, Galeichthys, Felichthys, and
- 39. other related genera. These are sleek, silvery fishes covered with smooth skin, the head usually with a coat of mail, pierced by a central fontanelle. Some of them reach a considerable size, swarming in sandy bays. None are valued as food, being always tough and coarsely flavored. Sea birds, as the pelican, which devour these catfishes are often destroyed by the sudden erection of the pectoral spines. None of these are found in Europe or in Japan. Of the very many American species the gaff-topsail catfish (Felichthys felis), noted for its very high spines, extends farthest north and is one of the very largest species. This genus has two barbels at the chin. Most others have four. The commonest sea catfish of the Carolina coast is Galeichthys milberti. In Tachysurus the teeth on the palate are rounded, in most of the others they are in villiform bands. Fig. 141.—Gaff-topsail Cat, Felichthys felis (L.). Wood's Hole.
- 40. Fig. 142.—Sea Catfish, Galeichthys milberti (Cuv. & Val.). Pensacola. In most or all of the sea catfish the eggs, as large as small peas, are taken into the mouth of the male and there cared for until hatched. The Channel Cats.—In all the rivers of North America east of the Rocky Mountains are found catfishes in great variety. The channel cats, Ictalurus, known most readily by the forked tails, are the largest in size and most valued as food. The technical character of the genus is the backward continuation of the supraoccipital, forming a bony bridge to the base of the dorsal. The great blue cat, Ictalurus furcatus, abounds throughout the large rivers of the Southern States and reaches a weight of 150 pounds or more. It is an excellent food and its firm flesh is readily cut into steaks. In the Great Lakes and northward is a very similar species, also of large size, which has been called Ictalurus lacustris. Another similar species is the willow cat, Ictalurus anguilla. The white channel-cat, Ictalurus punctatus, reaches a much smaller size and abounds on the ripples in clear swift streams of the Southwest, such as the Cumberland, the Alabama, and the Gasconade. It is a very delicate food-fish, with tender white flesh of excellent flavor.
- 41. Fig. 143.—Channel Catfish, Ictalurus punctatus (Rafinesque). Illinois River. Family Siluridæ. Horned Pout.—The genus Ameiurus includes the smaller brown catfish, horned pout, or bullhead. The body is more plump and the caudal fin is usually but not always rounded. The many species are widely diffused, abounding in brooks, lakes, and ponds. Ameiurus nebulosus is the best-known species, ranging from New England to Texas, known in the East as horned pout. It has been successfully introduced into the Sacramento, where it abounds, as well as its congener, Ameiurus catus (see Fig. 229, Vol. I), the white bullhead, brought with it from the Potomac. The latter species has a broader head and concave or notched tail. All the species are good food- fishes. All are extremely tenacious of life, and all are alike valued by the urchin, for they will bite vigorously at any sort of bait. All must be handled with care, for the sharp pectoral spines make an ugly cut, a species of wound from which few boys' hands in the catfish region are often free.
- 42. Fig. 144.—Horned pout, Ameiurus nebulosus (Le Sueur). (From life by Dr. R. W. Shufeldt.) In the caves about Conestoga River in Lancaster County, Pennsylvania, is a partly blind catfish, evidently derived from local species outside the cave. It has been named Gronias nigrilabris. A few species are found in Mexico, one of them, Ictalurus meridionalis, as far south as Rio Usamacinta on the boundary of Guatemala. Besides these, a large channel-cat of peculiar dentition, known as Istlarius balsanus, abounds in the basin of Rio Balsas. In Mexico all catfishes are known as Bagre, this species as Bagre de Rio. The genus Leptops includes the great yellow catfish, or goujon, known at once by the projecting lower jaw. It is a mottled olive and yellow fish of repulsive exterior, and it reaches a very great size. It is, however, a good food-fish. The Mad-toms.—The genera Noturus and Schilbeodes are composed of diminutive catfishes, having the pectoral spine armed
- 43. at base, with a poison sac which renders its sting extremely painful though not dangerous. The numerous species of this genus, known as "mad-toms" and "stone cats," live among weeds in brooks and sluggish streams. Most of them rarely exceed three inches in length, and their varied colors make them attractive in the aquarium. Fig. 145.—Mad-tom, Schilbeodes furiosus Jordan & Meek. Showing the poisoned pectoral spine. Family Siluridæ. Neuse River. The Old World Catfishes.—In the catfishes of the Old World and their relatives, the adipose fin is rudimentary or wanting. The chief species found in Europe is the huge sheatfish, or wels, Silurus glanis. This, next to the sturgeon, is the largest river fish in Europe, weighing 300 to 400 pounds. It is not found in England, France, or Italy, but abounds in the Danube. It is a lazy fish, hiding in the mud and thus escaping from nets. It is very voracious, and many stories are told of the contents of its stomach. A small child swallowed whole is recorded from Thorn, and there are still more remarkable stories, but not properly vouched for. The sheatfish is brown in color, naked, sleek, and much like an American Ameiurus save that its tail is much longer and more eel-like. Another large catfish, known to the ancients, but only recently rediscovered by Agassiz and Garman, is Parasilurus aristotelis of the rivers of Greece. In China and Japan is the very similar Namazu, or Japanese catfish, Parasilurus asotus, often found in ponds and used as food. Numerous smaller related
- 44. catfishes, Porcus (Bagrus), Pseudobagrus, and related genera swarm in the brooks and ponds of the Orient. Fig. 146.—Electric Catfish, Torpedo electricus (Gmelin). Congo River. (After Boulenger.) In the genus Torpedo (Malapterurus) the dorsal fin is wanting. Torpedo electricus, the electric catfish of the Nile, is a species of much interest to anatomists. The shock is like that of a Leyden jar. The structures concerned are noticed on p. 186, Vol. I. The generic name Torpedo was applied to the electric catfish before its use for the electric ray. In South America a multitude of genera and species cluster around the genus Pimelodus. Some of them have the snout very long and spatulate. Most of them possess a very long adipose fin. The species are generally small in size and with smooth skin like the North American catfishes. Still other species in great numbers are grouped around the genus Doras. In this group the snout projects, bearing the small mouth at its end, and the lateral line is armed behind with spinous shields. All but one of the genera belong to the Amazon district, Synodontis being found in Africa. Concerning Doras, Dr. Günther observes: "These fishes have excited attention by their habit of traveling during the dry season from a piece of water about to dry up in quest of a pond of greater capacity. These journeys are occasionally of such a length that the fish spends whole nights on the way, and the bands of scaly
- 45. travelers are sometimes so large that the Indians who happen to meet them fill many baskets of the prey thus placed in their hands. The Indians suppose that the fish carry a supply of water with them, but they have no special organs and can only do so by closing the gill-openings or by retaining a little water between the plates of their bodies, as Hancock supposes. The same naturalist adds that they make regular nests, in which they cover up their eggs with care and defend them, male and female uniting in this parental duty until the eggs are hatched. The nest is constructed, at the beginning of the rainy season, of leaves and is sometimes placed in a hole scooped out of the beach." The Sisoridæ.—The Sisoridæ are small catfishes found in swift mountain streams of northern India. In some of the genera (Pseudecheneis) in swift streams a sucking-disk formed of longitudinal plates of skin is formed on the breast. This enables these fishes to resist the force of the water. In one genus, Exostoma, plates of skin about the mouth serve the same purpose. The Bunocephalidæ are South American catfishes with the dorsal fin undeveloped and the top of the head rough. In Platystacus (Aspredo), the eggs are carried on the belly of the female, which is provided with spongy tentacles to which the eggs are attached. After the breeding season the ventral surface becomes again smooth. The Plotosidæ.—The Plotosidæ are naked catfishes, largely marine, found along the coasts of Asia. In these fishes the second dorsal is very long. Plotosus anguillaris, the sea catfish of Japan, is a small species striped with yellow and armed with sharp pectoral spines which render it a very disagreeable object to the fishermen. In sandy bays like that of Nagasaki it is very abundant. Allied to this is the small Asiatic family of Chacidæ. The Chlariidæ.—The Chlariidæ are eel-like, with a soft skeleton and a peculiar accessory gill. These abound in the swamps and muddy streams of India, where some species reach a length of six feet. One species, Chlarias magur, has been brought by the Chinese to Hawaii, where it flourishes in the same waters as Ameiurus
- 46. nebulosus, brought from the Potomac and by Chinese carried from San Francisco. The Hypophthalmidæ and Pygidiidæ.—The Hypophthalmidæ have the minute air-bladder inclosed in a long bony capsule. The eyes are placed very low and the skin is smooth. The statement that this family lacks the auditory apparatus is not correct. The few species belong to northern South America. Fig. 147.—An African Catfish, Chlarias breviceps Boulenger. Congo River. Family Chlariidæ. (After Boulenger.) Allied to this group is the family Pygidiidæ with a differently formed bony capsule and no adipose fin. The numerous species are all South American, mostly of mountain streams of high altitude. Some are very small. Certain species are said to flee for protection into the gill-cavity of larger catfishes. Some are reported to enter the urethra of bathers, causing severe injuries. The resemblance of certain species to the loaches, or Cobitidæ, is very striking. This similarity is due to the results of similar environment and necessarily parallel habits. The Argidæ have the capsule of the air-bladder formed in a still different fashion. The few species are very small, inhabitants of the streams of the high Andes. The Loricariidæ.—In the family of Loricariidæ the sides and back are armed with rough bony plates. The small air-bladder is still in a bony capsule, and the mouth is small with thick fringed lips. The numerous species are all small fishes of the South American waters,
- 47. bearing a strong external resemblance to Agonidæ, but wholly different in anatomy. The Callichthyidæ.—The Callichthyidæ are also small fishes armed with a bony interlocking coat of mail. They are closely allied to the Pygidiidæ. The body is more robust than in the Callichthyidæ and the coat of mail is differently formed. The species swarm in the rivers of northern South America, where with the mailed Loricariidæ they form a conspicuous part of the fish fauna. Fossil Catfishes.—Fossil catfishes are very few in number. Siluridæ, allied to Chlarias, Bagarius, Heterobranchus, and other fresh-water forms of India, are found in the late Tertiary rocks of Sumatra, and catfish spines exist in the Tertiary rocks of the United States. Vertebræ in the Canadian Oligocene have been referred by Cope to species of Ameiurus (A. cancellatus and A. maconnelli). Rhineastes peltatus and six other species, perhaps allied to Pimelodus, have been described by Cope from Eocene of Wyoming and Colorado. Bucklandium diluvii is found in the Eocene London clays, and several species apparently marine, referred to the neighborhood of Tachysurus or Arius, are found in Eocene rocks of England. There is no evidence that the group of catfishes has any great antiquity, or that its members were ever so numerous and varied as at the present time. The group is evidently derived from scaly ancestors, and its peculiarities are due to specialization of certain parts and degeneration of others. There is not the slightest reason for regarding the catfishes as direct descendants of the sturgeon or other Ganoid type. They should
- 48. Fig. 148.— Loricaria aurea Steindachner, a mailed Catfish from Rio Meta, Venezuela. Family Loricariidæ. (After Steindachner.) rather be looked upon as a degenerate and highly modified offshoot from the primitive Characins. Order Gymnonoti.—At the end of the series of Ostariophysans we may place the Gymnonoti (γυμνός, bare; νῶτος, back). This group contains about thirty species of fishes from the rivers of South America and Central America. All are eel-like in form, though the skeleton with the shoulder-girdle suspended from the cranium is quite unlike that of a true eel. There is no dorsal fin. The vent is at the throat and the anal is excessively long. The gill-opening is small as in the eel, and as in most elongate fishes, the ventral fins are undeveloped. The body is naked or covered with small scales. Two families are recognized, differing widely in appearance. The Electrophoridæ constitutes by itself Cope's order of Glanencheli (γλανίς, catfish; ἔγχελυς, eel). This group he regards as intermediate between the eel-like catfishes (Chlarias) and the true eels. It is naked and eel-shaped, with a short head and projecting lower jaw like that of the true eel. The single species, Electrophorus electricus, inhabits the rivers of Brazil, reaching a length of six feet, and is the most powerful of all electric fishes. Its electric organs on the tail are derived from modified muscular tissue. They are described on p. 170, Vol. I. The Gymnotidæ are much smaller in size, with compressed scaly bodies and the mouth at the end of a long snout. The numerous species are all fishes without electric organs. Eigenmannia humboldti of the Panama region is a characteristic species. No fossil Gymnonoti are recorded.
- 49. CHAPTER X THE SCYPHOPHORI, HAPLOMI, AND XENOMI rder Scyphophori.—The Scyphophori (σκύφος, cup; φορέω, to bear) constitutes a small order which lies apparently between the Gymnonoti and the Isospondyli. Boulenger unites it with the Isospondyli. The species, about seventy-five in number, inhabit the rivers of Africa, where they are important as food-fishes. In all there is a deep cavity on each side of the cranium covered by a thin bony plate, the supertemporal bone. There is no symplectic bone, and the subopercle is very small or concealed. The gill-openings are narrow and there are no pharyngeal teeth. The air-bladder connects with the ear, but not apparently in the same way as with the Ostariophysan fishes, to which, however, the Scyphophori are most nearly related. In all the Scyphophori the body is oblong, covered with cycloid scales, the head is naked, there are no barbels, and the small mouth is at the end of a long snout. All the species possess a peculiar organ on the tail, which with reference to a similar structure in Torpedo and Electrophorus is held to be a degenerate electric organ. According to Günther, "it is without electric functions, but evidently representing a transitional condition from muscular substance to an electric organ. It is an oblong capsule divided into numerous compartments by vertical transverse septa and containing a gelatinous substance." The Mormyridæ.—There are two families of Scyphophori. The Mormyridæ have the ordinary fins and tail of fishes and the Gymnarchidæ are eel-like, with ventrals, anal and caudal wanting.
- 50. Gymnarchus miloticus of the Nile reaches a length of six feet, and it is remarkable as retaining the cellular structure of the air-bladder as seen in the garpike and bowfin. It doubtless serves as an imperfect lung. The best-known genus of Scyphophori is Mormyrus. Species of this genus found in the Nile were worshiped as sacred by the ancient Egyptians and pictures of Mormyrus are often seen among the emblematic inscriptions. The Egyptians did not eat the Mormyrus because with two other fishes it was accused of having devoured a limb from the body of Osiris, so that Isis was unable to recover it when she gathered the scattered remains of her husband. In Mormyrus the bones of the head are covered by skin, the snout is more or less elongated, and the tail is generally short and insignificant. One of the most characteristically eccentric species is Gnathonemus curvirostris, lately discovered by Dr. Boulenger from the Congo. Fossil Mormyridæ are unknown. Fig. 149.—Gnathonemus curvirostris Boulenger. Family Mormyridæ. Congo River. (After Boulenger.) The Haplomi.—In the groups called Iniomi and Lyopomi, the mesocoracoid arch is imperfect or wanting, a condition which in some cases may be due to the degeneration produced by deep-sea
- 51. life. In the eels a similar condition obtains. In the group called Haplomi (ἁπλοός, simple; ὤμος, shoulder), as in all the groups of fishes yet to be discussed, this arch is wholly wanting at all stages of development. In common with the Isospondyli and with soft-rayed fishes in general the air-bladder has a persistent air-duct, all the fins are without true spines, the ventral fins are abdominal, and the scales are cycloid. The group is a transitional one, lying almost equidistant between the Isospondyli and the Acanthopterygii. Gill unites it with the latter and Woodward with the former. We may regard it for the present as a distinct order, although no character of high importance separates it from either. Hay unites the Haplomi with the Synentognathi to form the order of Mesichthyes, or transitional fishes, but the affinities of either with other groups are quite as well marked as their relation to each other. Boulenger unites the Iniomi with the Haplomi, an arrangement which apparently has merit, for the most primitive and non-degenerate Iniomi, as Aulopus and Synodus, lack both mesocoracoid and orbitosphenoid. These bones are characteristic of the Isospondyli, but are wanting in Haplomi. There is no adipose dorsal in the typical Haplomi, the dorsal is inserted far back, and the head is generally scaly. Most but not all of the species are of small size, living in fresh or brackish water, and they are found in almost all warm regions, though scantily represented in California, Japan, and Polynesia. The four families of typical Haplomi differ considerably from one another and are easily distinguished, although obviously related. Several other families are provisionally added to this group on account of agreement in technical characters, but their actual relationships are uncertain. The Pikes.—The Esocidæ have the body long and slender and the mouth large, its bones armed with very strong, sharp teeth of different sizes, some of them being movable. The upper jaw is not projectile, and its margin, as in the Salmonidæ, is formed by the maxillary. The scales are small, and the dorsal fin far back and opposite the anal, and the stomach is without pyloric cæca. There is but a single genus, Esox (Lucius of Rafinesque), with about five or
- 52. six living species. Four of these are North American, the other one being found in Europe, Asia, and North America. All the pikes are greedy and voracious fishes, very destructive to other species which may happen to be their neighbors; "mere machines for the assimilation of other organisms." Thoreau describes the pike as "the swiftest, wariest, and most ravenous of fishes, which Josselyn calls the river-wolf. It is a solemn, stately, ruminant fish, lurking under the shadow of a lily-pad at noon, with still, circumspect, voracious eye; motionless as a jewel set in water, or moving slowly along to take up its position; darting from time to time at such unlucky fish or frog or insect as comes within its range, and swallowing it at one gulp. Sometimes a striped snake, bound for greener meadows across the stream, ends its undulatory progress in the same receptacle." Fig. 150.—The Pike, Esox-lucius L. (From life by R. W. Shufeldt.) As food-fishes, all the Esocidæ rank high. Their flesh is white, fine- grained, disposed in flakes, and of excellent flavor.
- 53. The finest of the Esocidæ, a species to be compared, as a grand game fish, with the salmon, is the muskallunge (Esox masquinongy). Technically this species may be known by the fact that its cheeks and opercles are both naked on the lower half. It may be known also by its great size and by its color, young and old being spotted with black on a golden-olive ground. Fig. 151.—Muskallunge, Esox masquinongy Mitchill. Ecorse, Mich. The muskallunge is found only in the Great Lake region, where it inhabits the deeper waters, except for a short time in the spring, when it enters the streams to spawn. It often reaches a length of six feet and a weight of sixty to eighty pounds. It is necessarily somewhat rare, for no small locality would furnish food for more than one such giant. It is, says Hallock, "a long, slim, strong, and swift fish, in every way formed for the life it leads, that of a dauntless marauder." A second species of muskallunge, Esox ohiensis, unspotted but vaguely cross-barred, occurs sparingly in the Ohio River and the upper Mississippi Valley. It is especially abundant in Chautauqua Lake. The pike (Esox lucius) is smaller than the muskallunge, and is technically best distinguished by the fact that the opercles are naked below, while the cheeks are entirely scaly. The spots and cross-bars in the pike are whitish or yellowish, and always paler than the olive- gray ground color. It is the most widely distributed of all fresh-water
- 54. fishes, being found from the upper Mississippi Valley, the Great Lakes, and New England to Alaska and throughout northern Asia and Europe. It reaches a weight of ten to twenty pounds or more, being a large strong fish in its way, inferior only to the muskallunge. In England Esox lucius is known as the pike, while its young are called by the diminutive term pickerel. In America the name pickerel is usually given to the smaller species, and sometimes even to Esox lucius itself, the word being with us a synonym for pike, not a diminutive. Of the small pike or pickerel we have three species in the eastern United States. They are greenish in color and banded or reticulated, rather than spotted, and, in all, the opercles as well as the cheeks are fully covered with scales. One of these (Esox reticulatus) is the common pickerel of the Eastern States, which reaches a respectable size and is excellent as food. The others, Esox americanus along the Atlantic seaboard and Esox vermiculatus in the middle West, seldom exceed a foot in length and are of no economic importance. Numerous fossil species are found in the Tertiary of Europe, Esox lepidotus from the Miocene of Baden being one of the earliest and the best known; in this species the scales are much larger than in the recent species. The fossil remains would seem to indicate that the origin of the family was in southern Europe, although most of the living species are American.
- 55. Fig. 152.—Mud-minnow, Umbra pygmæa (De Kay). New Jersey. The Mud-minnows.—Close to the pike is the family of Umbridæ, or mud-minnows, which technically differ from the pikes only in the short snout, small mouth, and weak dentition. The mud-minnows are small, sluggish, carnivorous fishes living in the mud at the bottom of cold, clear streams and ponds. They are extremely tenacious of life, though soon suffocated in warm waters. The barred mud-minnow of the prairies of the middle West (Umbra limi) often remains in dried sloughs and bog-holes, and has been sometimes plowed up alive. Umbra pygmæa, a striped species, is found in the Eastern States and Umbra crameri in bogs and brooks along the Danube. This wide break in distribution seems to indicate a former wide extension of the range of Umbridæ, perhaps coextensive with Esox. Fossil Umbridæ are, however, not yet recognized. The Killifishes.—Most of the recent Haplomi belong to the family of Pœciliidæ (killifishes, or Cyprinodonts). In this group the small mouth is extremely protractile, its margin formed by the premaxillaries alone much as in the spiny-rayed fishes. The teeth are small and of various forms according to the food. In most of the herbivorous forms they are incisor-like, serrate, and loosely inserted in the lips. In the species that eat insects or worms they are more firmly fixed. The head is scaly, the stomach without cæca, and the intestines are long in the plant-eating species and short in the others. There are nearly 200 species, very abundant from New England and California southward to Argentina, and in Asia and Africa also. In regions where rice is produced, they swarm in the rice swamps and ditches. Some of them enter the sea, but none of them go far from shore. Some are brilliantly colored, and in many species the males are quite unlike the females, being smaller and more showy. The largest species (Fundulus, Anableps) rarely reach the length of a foot, while Heterandria formosa, a diminutive inhabitant of the Florida rivers, scarcely reaches an inch. Some species are
- 56. oviparous, but in most of the herbivorous forms, and some of the others, the eggs are hatched within the body, and the anal in the male is modified into a long sword-shaped intromittent organ, placed farther forward than the anal in the female. The young when born closely resemble the parent. Most of the insectivorous species swim at the surface, moving slowly with the eyes partly out of water. This habit in the genus Anableps (four-eyed fish, or Cuatro ojos) is associated with an extraordinary structure of the eye. This organ is prominent and is divided by a horizontal partition into two parts, the upper, less convex, adopted for sight in the air, the lower in the water. The few species of Anableps are found in tropical America. The species of some genera swim near the bottom, but always in very shallow waters. All are very tenacious of life, and none have any commercial value although the flesh is good. Fig. 152a.—Four-eyed Fish, Anableps dovii Gill. Tehuantepec, Mexico. The unique structure of the eye of this curious fish has been carefully studied by Mr. M. C. Marsh, pathologist of the U. S. Fish Commission, who furnishes the following notes published by Evermann & Goldsborough: "The eye is crossed by a bar, like the diameter of a circle, and parallel with the length of the body. This bar is darker than the other external portions of the eyeball and has its edges darker still. Dividing the external aspect of the eye equally, it has its lower edge on the same level as the back of the fish, which is flat and straight from snout to dorsal, or nearly the whole length of the fish; so that
- 57. when the body of the fish is just submerged the level of the water reaches to this bar, and the lower half of the eye is in water, the upper half in the air. Upon dissecting the eyeball from the orbit, it appears nearly round. A membranous sheath covers the external part and invests most of the ball. It may be peeled off, when the dark bar on the external portion of the eye is seen to be upon this membrane, which may correspond to the conjunctiva. The back portion of the eyeball being cut off, one lens is found. The lining of the ball consists, in front, of one black layer, evidently choroid. Behind there is a retinal layer. The choroid layer turns up anteriorly, making a free edge comparable to an iris. The free edge is chiefly evident in the lower part of the eye. A large pupil is left, but is divided by two flaps, continuations of the choroid coat, projecting from either side and overlapping. There are properly then two pupils, an upper and lower, separated by a band consisting of the two flaps, which may probably, by moving upward and downward, increase or diminish the size of either pupil; an upward motion of the flaps increasing the lower pupil at the expense of the other, and vice versa." This division of the pupil into two parts permits the fish, when swimming at the surface of the water, as is its usual custom, to see in the air with the upper portion and in the water with the lower. It is thus able to see not only such insects as are upon the surface of the water or flying in the air above, but also any that may be swimming beneath the surface.
- 58. Fig. 153.—Round Minnow, Cyprinodon variegatus Lacépède. St. George Island, Maryland. According to Mr. E. W. Nelson, "the individuals of this species swim always at the surface and in little schools arranged in platoons or abreast. They always swim headed upstream against the current, and feed upon floating matter which the current brings them. A platoon may be seen in regular formation breasting the current, either making slight headway upstream or merely maintaining their station, and on the qui vive for any suitable food the current may bring. Now and then one may be seen to dart forward, seize a floating food particle, and then resume its place in the platoon. And thus they may be observed feeding for long periods. They are almost invariably found in running water well out in the stream, or at least where the current is strongest and where floating matter is most abundant, for it is upon floating matter that they seem chiefly to depend. They are not known to jump out of the water to catch insects flying in the air or resting upon vegetation above the water
- 59. surface, nor do they seem to feed to any extent upon all small crustaceans or other portions of the plankton beneath the surface. Fig. 154.—Everglade Minnow, Jordanella floridæ Goode & Bean. Everglades of Florida. "When alarmed—and they are wary and very easily frightened—they escape by skipping or jumping over the water, 2 or 3 feet at a skip. They rise entirely out of the water, and at a considerable angle, the head pointing upward. In descending the tail strikes the water first and apparently by a sculling motion new impetus is acquired for another leap. This skipping may continue until the school is widely scattered. When a school has become scattered, and after the cause of their fright has disappeared, the individuals soon rejoin each other. First two will join each other and one by one the others will join them until the whole school is together again. Rarely do they attempt to dive or get beneath the surface; when they do they have great difficulty in keeping under and soon come to the surface again."
- 60. Fig. 155.—Mayfish, Fundulus majalis (L.) (male). Wood's Hole. Fig. 156.—Mayfish, Fundulus majalis (female). Wood's Hole.
- 61. Fig. 157.—Top-minnow, Zygonectes notatus (Rafinesque). Eureka Springs, Ark. Fig. 158.—Death Valley Fish, Empetrichthys merriami Gilbert. Amargosa Desert, Cal. Family Pœciliidæ. (After Gilbert.) Fig. 159.—Sword-tail Minnow, male, Xiphophorus helleri Heckel. The anal fin modified as an intromittent organ. Vera Cruz. Of the many genera of Pœciliidæ, top-minnows, and killifishes we may mention the following: Cyprinodon is made up of chubby little fishes of eastern America with tricuspid, incisor teeth, oviparous and
- 62. omnivorous. Very similar to these but smaller are the species of Lebias in southern Europe. Jordanella floridæ of the Florida everglades is similar, but with the dorsal fin long and its first ray enlarged and spine-like. It strongly resembles a young sunfish. Most of the larger forms belong to Fundulus, a genus widely distributed from Maine to Guatemala and north to Kansas and southern California. Fundulus majalis, the Mayfish of the Atlantic Coast, is the largest of the genus. Fundulus heteroclitus, the killifish, the most abundant. Fundulus diaphanus inhabits sea and lake indiscriminately. Fundulus stellifer of the Alabama is beautifully colored, as is Fundulus zebrinus of the Rio Grande. The genus Zygonectes includes dwarf species similar to Fundulus, and Adinia includes those with short, deep body. Goodea atripinnis with tricuspid teeth lives in warm springs in Mexico, and several species of Goodea, Gambusia, Pœcilia, and other genera inhabit hot springs of Mexico, Central America, and Africa. The genus Gambusia, the top-minnows, includes numerous species with dwarf males having the anal modified. Gambusia affinis abounds in all kinds of sluggish water in the southern lowlands, gutters and even sewers included. It brings forth its brood in early spring. Viviparous and herbivorous with modified anal fin are the species of Pœcilia, abundant throughout Mexico and southward to Brazil; Mollienesia very similar, with a banner-like dorsal fin, showily marked, occurs from Louisiana southward, and Xiphophorus, with a sword-shaped lobe on the caudal, abounds in Mexico; Characodon and Goodea (see Fig. 53, Vol. I) in Mexico have notched teeth, and finally, Heterandria contains some of the least of fishes, the handsomely colored males barely half an inch long.
- 63. Fig. 160.—Goodea luitpoldi (Steindachner). A viviparous fish from Lake Patzcuaro, Mexico. Family Pœciliidæ. (After Meek.) In Lake Titicaca in the high Andes is a peculiar genus (Orestias) without ventral fins. Still more peculiar is Empetrichthys merriami of the desert springs of the hot and rainless Death Valley in California, similar to Orestias, but with enormously enlarged pharyngeals and pharyngeal teeth, an adaptation to some unknown purpose. Fossil Cyprinodonts are not rare from the Miocene in southern Europe. The numerous species are allied to Lebias and Cyprinodon, and are referred to Prolebias and Pachylebias. None are American, although two American extinct genera, Gephyrura and Proballostomus, are probably allied to this group. Amblyopsidæ.—The cavefishes, Amblyopsidæ, are the most remarkable of the haplomous fishes. In this family the vent is placed at the throat. The form is that of the Pœciliidæ, but the mouth is larger and not protractile. The species are viviparous, the young being born at about the length of a quarter of an inch.
- 64. Fig. 161.—Dismal Swamp Fish, Chologaster cornutus Agassiz. Supposed ancestor of Typhlichthys. Virginia. In the primitive genus Chologaster, the fish of the Dismal Swamp, the eyes are small but normally developed. Chologaster cornutus abounds in the black waters of the Dismal Swamp of Virginia, thence southward through swamps and rice-fields to Okefinokee Swamp in northern Florida. It is a small fish, less than two inches long, striped with black, and with the habit of a top-minnow. Other species of Chologaster, possessing eyes and color, but provided also with tactile papillæ, are found in cave springs in Tennessee and southern Illinois. Fig. 162.—Blind Cave-fish, Typhlichthys subterraneus Girard. Mammoth Cave, Kentucky. From Chologaster is directly descended the small blindfish Typhlichthys subterraneus of the caves of the Subcarboniferous limestone rocks of southern Indiana and southward to northern
- 65. Alabama. As in Chologaster, the ventral fins are wanting. The eyes, present in the young, become defective and useless in the adult, when they are almost hidden by other tissues. The different parts of the eye are all more or less incomplete, being without function. The structure of the eye has been described in much detail in several papers by Dr. Carl H. Eigenmann. As to the cause of the loss of eyesight two chief theories exist—the Lamarckian theory of the inheritance in the species of the results of disuse in the individual and the Weissmannian doctrine that the loss of sight is a result of panmixia or cessation of selection. This may be extended to cover reversal of selection, as in the depths of the great caves the fish without eyes would be at some slight advantage. Dr. Eigenmann inclines to the Lamarckian doctrine, but the evidence brought forward fails to convince the present writer that results of individual use or disuse ever become hereditary or that they are ever incorporated in the characters of a species. In the caves of southern Missouri is an independent case of similar degradation. Troglichthys rosæ, the blindfish of this region, has the eye in a different phase of degeneration. It is thought to be separately descended from some other species of Chologaster. Of this species Mr. Garman and Mr. Eigenmann have given detailed accounts from somewhat different points of view. Concerning the habits of the blindfish (Troglichthys rosæ), Mr. Garman quotes the following from notes of Miss Ruth Hoppin, of Jasper County, Missouri: "For about two weeks I have been watching a fish taken from a well. I gave him considerable water, changed once a day, and kept him in an uninhabited place subject to as few changes of temperature as possible. He seems perfectly healthy and as lively as when first taken from the well. If not capable of long fasts, he must live on small organisms my eye cannot discern. He is hardly ever still, but moves about the sides of the vessel constantly, down and up, as if needing the air. He never swims through the body of the water away from the sides unless disturbed. Passing the finger over the sides of the vessel under water I find it slippery. I am careful not to disturb this slimy coating when the water is
- 66. Welcome to our website – the ideal destination for book lovers and knowledge seekers. With a mission to inspire endlessly, we offer a vast collection of books, ranging from classic literary works to specialized publications, self-development books, and children's literature. Each book is a new journey of discovery, expanding knowledge and enriching the soul of the reade Our website is not just a platform for buying books, but a bridge connecting readers to the timeless values of culture and wisdom. With an elegant, user-friendly interface and an intelligent search system, we are committed to providing a quick and convenient shopping experience. Additionally, our special promotions and home delivery services ensure that you save time and fully enjoy the joy of reading. Let us accompany you on the journey of exploring knowledge and personal growth! textbookfull.com