2 — ame = i = oe - a > = = > a PUES epee! PU be PRINCIPLES OF ECONOMIC ZOOLOGY BY L. S. DAUGHERTY, M.S., Ph.D. PROFESSOR OF ZOOLOGY, STATE NORMAL SCHOOL, KIRKSVILLE, MO. AND M. C. DAUGHERTY AUTHOR WITH JACKSON OF ‘‘AGRICULTURE THROUGH THE LABORATORY AND SCHOOL GARDEN” SECOND EDITION, REVISED WITH 301 ILLUSTRATIONS PHILADELPHIA AND LONDON We Bs SAUNDERS. COMPANY 1917 Copyright, 1912, by W. B. Saunders Company. Reprinted May, 1915. Revised, reprinted, and recopyrighted September, 1917 Copyright, 1917, by W. B. Saunders Company PRINTED IN AMERICA PRESS OF W. B. SAUNDERS COMPANY PHILADELPHIA ©o1a473152 PREFACE TO THE SECOND EDITION Tue authors have corrected some errors that crept into the first edition. We have added suggestions, problems, and questions which we hope will be of use to our fellow teachers. We have diligently compared our text with the latest Ger- man, French, English, and American Zoélogies, and we be- lieve we have given the correct facts. THE AUTHORS. September, 1917. il oes aa Pei wer ee Tur authors have long felt the need of one book in the hands of the student which would give not only the salient facts of structural Zodlogy and the development of the various branches of animals, but also such facts of natural history—or the life and habits of animals—as to show the interrelations of structure, habit, and environment. For we believe that a knowledge of both structure and life-history is necessary before any suggestions or discoveries can be made concerning the prin- ciples which underlie and control all animal life, including that of man. For it is principles and their application for which we are searching. This book is an attempt to supply this need. It is especi- ally designed to accompany the “Field and Laboratory Guide” (Part I). For the sake of the natural history many examples have been included. To reduce the size of the book it has been necessary to print this natural history in smaller type, but that in no way implies that it is of mimor importance, and it is by far the most interesting portion of the subject. The scien- tific names need not, in all cases, be learned. They have been used because common names are so often misleading. v vi PREFACE Much of the subject matter has been derived from our own observation and experience, but we have made use of material from all available sources and we have tried to give credit by continual reference to the authorities used. That a book of this character can never be original; everyone knows. The scope is too great for the observations of one lifetime. We are aware that we have fallen far short of our ideal. But we believe the book will be of much service if followed as suggested and used in connection with Part I. “Tf a better system is thine, impart it frankly. If not, make use of mine.” THE AUTHORS. KirKsviLie, Mo. CONTENTS : PAGE VAIN @ Eee AR OR OZ OVACa a esis vsis ances, = ate rdw papas eM in Aine an dames 1 Class I. Rhizopoda, 1.—Class II. Mastigophora, 4.—Class III. Sporozoa, 4——Class IV. Infusoria, 5. VAIN Hie OR MEE RUAG Gs fy 4h Aeon ie atl ee rote Oarie bla Newnan Satie teh Nic, aeons ae) A wap on sate 10 BPAINICHIs ©. CHERINDRFUATA sen sop firs cael een mn wed sides See ul gis uel ate acees/ ai ars 17 Class I. Hydrozoa, 18.—Class II. The Scyphozoa, 26.—Class III. Actinozoa, 26.—Class IV. Ctenophora, 31. : BRANCH URL AT YEMEMIUN THES. 2f.y5 sa scisc -telets ely ses bees eee s Socceis Sika 34 Class I. Turbellaria, 34.—Class II. Trematoda, 35.—Class III. Cestoda, 37.—Class IV. Nemertinea, 39. BRANCH INEMATHNLMINTHES. 5.2.5.0 .50.00c000050-000hs00550 00% Al Class I. Nematoda, 41.—Class II. Acanthocephala, 44.—Class III. Chetognatha, 44. BRANCH (RROCHELMINTHES .20200 2. 5. occ oe sce ek oe de ok eek be Class I. Rotifera, 46.—Class II. Dinophilea, 47.—Class III. Gastrotricha, 47. BRANCH VIOMEUSCOLDAS xa aki folds ae bonnes) nee coe ike oko a 48 Class I. Polyzoa, 48.—Class II. Phoronida, 48.—Class III. Brachiopoda, 48. ES EZAUN CO Hash CHUN ODEIENUAT A Mistey elf) eacy eons Svcs Sue seep Pees Bt ska See ere 50 Class I. Asteroidea, 54.—Class II. Ophiuroidea, 56.—Class III. Kchinoidea, 58.—Class IV. Holothuroidea, 60.—Class V. Crinoidea, 62. EPUN OIE AUNIN UD AUD AGS ee eras nist 8a tae ales ue Ve AD SA re ook 65 Class I. Chetopoda, 65.—Class II. Gephyrea, 69.—Class III. Hirudinea, 69. LENE JNIRICIET JNO ORSL CUES ae re cai a lo a a 72 Class I. Pelecypoda, 73.—Class II. Gasteropoda, 81.—Class ITI. Cephalopoda, 84. vii viii CONTENTS BRANGE ARTHROPODA idee ole hayes eeletste che sot cairn a ane niet nana Class I. Crustacea, 90.—Sub-class Entomostraca, 90,—Order I. Phyllopoda, 90.—Order II. Ostracoda, 90.—Order III. Cope- poda, 91.—Order IV. Cirripedia or Barnacles, 91.—Sub-class {l. Malacostraca, 92.—Order I. Phyllocardia, 93.—Order II. Decapoda, 93.—Order IIL. Arthrostraca, 102. Class II. Arachnida, 103.—Order I. Scorpionida, 103.—Order Il. Phalangidea, 104.—Order III. Araneida or Spiders, 104.— Order IV. Xiphosura, 110. Class III. Myriapoda, 111.—Order I. Chilopoda, 111.—Order Il. Diplopoda, 112. Class IV. Insects, 112.—Order I. Aptera or Thysanura, 126.— Order II. Ephemerida, 127—Order III. Plecoptera, 128.— Order IV. Odonata, 129.—Order V. Isoptera, 131.—Order VI. Orthoptera, 132.—Order VII. Hemiptera, 140.—Order VIII. Coleoptera, 148.—Order IX. Diptera, 153.—Order X. Siphon- aptera, 161.—Order XI. Lepidoptera, 162.—Order XII. Hymen- optera, 174. BRANCH. CHORD ATAsH 22 dipsiclo is ain en eben me Suet felts tcc ee Sub-phylum and Class I. Adelochorda, 191.—Sub-phylum and Class II. Urochorda or Tunicata, 192.—Sub-phylum and Class III. Acrania or Amphioxus, 194. Sub-phylum, IV. Craniata or Vertebrata, 195.—Class I. Cy- clostomata, 195. Class II. Pisces, 196.—Sub-class I. Elasmobranchu, 206.— Sub-class II. Holocephali, 207.—Sub-class III. Dipnoi, 208.— Sub-class IV. Teleostomi, 209.—Order If. Crossopterygn, 210.— Order II. Chondrostei, 210.—Order ILI. Holostei, 210.—Order IV. Teleostei, 211. Class III. Amphibia, 221.—Order I. Stegocephala, 228.—Order Il. Apoda or Gymnophiona, 228.—Orddr III. Urodela or Cau- data, 229.—Order IV. Anura or Ecaudata, 233. Class IV. Reptilia, 236.—Order I. Rhynchocephalia, 238.— Order II. Ophidia, 239.—Order III. Lacertilia, 243.—Order IV. Chelonia, 248.—Order V. Crocodilia, 253. Class V. Aves, 258.—Division A. Ratite, 278.—Diision B. Carinate, 281.—Water Birds: Order I. Pygopodes, 281.—Order Il. Longipennes, 282.—Order III. Tubinares, 283.—Order IV. Steganopodes, 284.—Order V. Anseres, 285.—Order VI. Odon- toglosse, 286.—Order VII. Herodiones, 286.—Order VIII. Paludicole, 289.—Order IX. Limicolw, 290.—Land Birds: Order X. Galline, 291.—Order XI. Columb, 292.—Order XII. Raptores, 294.—Order XIII. Psittaci, 297.—Order XIV. Coccyges, 297.—Order XV. Pici, 298.—Order XVI. Machro- chires, 300.—Order XVII. Passeres, 300. oo CONTENTS 1x PAGE Class VI. Mammalia, 311.—Order I. Monotremata, 319.— Order II. Marsupialia, 320.—Order III. Edentata, 323.—Order IV. Sirenia, 325.—Order V. Cetacea, 326.—Order VI. Ungulata, 329.—Order VII. Rodentia or Glires, 350.—Order VIII. Car- nivora, 356.—Order IX. Insectivora, 366.—Order X. Chirop- tera, 368.—Order XI. Primates, 372. THEORIES OF DEVELOPMENT...........0cccccccecccecccceesaees 382 QUESTIONS, PROBLEMS, AND SUGGESTIONS.............----++..05. 394 (CeO SSA Yooper eee tunis cs ee Sa an ead oly Le ree OR eer) ee De Leen St co 413 ‘‘There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.” SHAKESPEARE. PRINGIPLES OF mEeONOMIC ZOOLOGY BRANCH PROTOZOA TE: animals of this branch are one celled and microscopic, or very small. These cells may unite, but as the union is not organic, it is said to form a colony, and not an individual animal as is the case in the higher forms. A colony may consist of a few cells, as in Gonium, or of many cells, as in Volvox. Since protozoans are so minute and their soft protoplasmic substance is so easily dried up, they are usually aquatic, but some forms are parasitic, while others, as Ame’ba terric’ola, are terrestrial, but these live or remain active in moist places only. Protozoans are most abundant in salt water, or in stagnant pools of fresh water, and are found in almost all parts of the globe. Since, by reason of their simplicity, protozoans are adapted for living where other animals could not exist, they are supposed to be the oldest or first animal life, and it is believed that they existed in the Archean time. (See Fig. 302.) Numbers.—There are many thousands of species of these protozoans, each species differing from all others in some detail, yet all agreeing in their unicellular simplicity. Only a few of the typical forms can be mentioned. CLASS I. RHIZOPODA The lowest class, or Rhizdp’oda, is represented by the Ameba (Fig. 1). It is an irregular mass of colorless, semifluid, or jelly- like living protoplasm destitute of a cell wall. There is no dis- 1 2 BRANCH PROTOZOA tinct line between the clear outer homogeneous layer, or ecto- plasm, and the inner granular substance, the endoplasm. Within the endoplasm is the nucleus, a small, round, denser mass. Sometimes the contractile vacuole, a clear sphere of liquid and gas, appears, increases in size, then contracts, and disappears, and a new one isformed. This is supposed to aid in respiration Fig. 1.—Ameba polypodia in six successive stages of division. The dark white-edged spot in the interior is the nucleus. (Schulze.) and in carrying off the waste products formed by oxidation, such as carbon dioxid. Motion and Locomotion.— Under the microscope the amceba may be identified by its movements. The body surface will be seen to protrude or rather flow out at one or several points, forming irregular lobes, called false feet, or pseudopodia, which RHIZOPODA 3 may be contracted, or the whole body protoplasm may flow along after them, thus producing locomotion as well as constant change of form. According to the experiments of Professor H. 8. Jennings, particles attached to the ectoplasm move forward on the upper surface, disappear over the anterior edge, and, as the proto- plasm flows along, appear again at the posterior end, to repeat the circuit, showing that this locomotion is a sort of “ rolling -process.”’ Feeding.—As the amceba flows or rolls along, if it comes in contact with a particle which is unfit for food, it passes by or over it, but if the particle is fit for food, it flows about and en- velops it, and forms the so-called food vacuole. As this food vacuole moves along the endoplasm, the digestible part of the food disappears in digestion, while the indigestible portion is left behind as the protoplasmic body moves along. Multiplication in the case of the Ameba is by binary division or fission and by sporulation. This becomes necessary, since the entire animal is but a single cell, and all the functions for the whole animal must be performed by this one cell. Hence, it must remain exceedingly small, so the nucleus, as well as the body substance, dividés into two halves, and two individuals result. Encysting —Under unfavorable environment, such as drouth, the Ameba contracts into a tiny sphere, becomes encysted or encased in a horn-like membrane, and remains in a dormant condition until favorable environment returns to it, or it is trans- ported by the wind or carried by other animals—in the dirt which has clung to them—to a favorable environment, where it bursts its cyst and resumes active life. The Radiola’ria are marine Rhizopoda which have their pseudopodia arranged like rays. Many of these forms possess a silicious shell or skele- ton, and myriads of these shells are found in rocks of various geologic ages. One type reproduces by swarm spores, the original nucleus dividing into hundreds of daughter-nuclei. The Foraminif’era are Rhizopoda whose fresh-water forms have chitinous or silicious coverings, while the typical members, which are marine, have calcareous shells. When the animal dies the shell sinks to the bottom of the ocean. Such multitudes have existed that vast formations of chalk or limestone rock have been made by their shells. The stone of the Pyra- mids is said to be composed of fossil Foraminifera. 4 BRANCH PROTOZOA It is said that in the bodies of some Radiolaria are found unicellular Algee, or microscopic plants, which furnish, even in this low stage of life, an example of symbiosis, or the living together of different kinds of organisms for mutual benefit. CLASS II. MASTIGOPHORA The Eugle’na is a representative of the second class of Pro- tozoans (Mastigoph’ora). It has a more fixed arrangement of parts than the Ameba. The cell is surrounded by a delicate membrane perforated at the blunt anterior end by a funnel- shaped mouth through which the food passes into the body sub- stance. From the base of this mouth the protoplasm extends out in a long flagellum which, by its lashing, propels the body forward, and produces currents of water which bear food into the mouth. Back of the mouth is a tiny pigment spot beside a clear space which is sensitive to light. CLASS III. SPOROZOA This class consists of parasitic protozoans. The Gregari’na is parasitic in the intestines, reproductive organs, or, rarely, in the body cavity of invertebrates, such as crayfish, insects, and worms. It absorbs liquid food from its host and has no mouth nor pseudopodia. One or two individuals become encysted and then break up into a number of minute portions called spores. The Hemosporid’ia are sporozoans which live in the blood-corpuscles of vertebrates. In man they are the germs which produce malaria. The malaria-producing protozoans spend part of their life in man and part in a certain genus of mosquito Anoph’eles). When this mosquito sucks the blood of a malarial patient the germs are taken into the stomach of the mosquito. ‘‘ After fertilization the odsphere wanders into the intestinal wall of the mosquito, grows larger, encysts, and produces many sporo- blasts, which in time form many sporozoites.’ These pass out with the saliva of the female Anopheles as it “ bites ”’ another person, and thus the germs of malaria are transferred to his blood, where, under proper condi- tions, they multiply rapidly, and fever results. It is evident that the bite of this mosquito does not cause malaria unless the mosquito is itself in- fected with the germs. Yellow fever is believed to be caused by another sporozoan carried by a different genus of mosquito (Stegomy’ia). (See p. 157.) INFUSORIA CLASS IV. INFUSORIA The fourth class of protozoans is the Infuso’ria, of which the Paramecium, or “slipper animalcule,” is a type (Fig. 2). It is somewhat cylindric in form and is surrounded by a cuticle perforated with minute openings, through which the protoplasm projects in the form of short hair-like structures, called cilia, which are the organs of locomotion. On the ventral surface of the Paramoecium is a groove which runs backward and inward into a short tube or gullet. Both the tube and the gullet are lined with vibrating cilia which cause currents of water. These currents carry the food into the inner end of the gullet, where it is pushed by occasional constrictions into the soft endoplasm and carried about in its movements as a food vacuole. The un- digested particles are cast out at a fixed point in the cell wall, but it is not per- manently open, so it is not easily recog- nized. The Paramcecium is supplied with two coiled threads which may be used as organs of defense. The Paramcecium has two nuclei, one, the macronucleus, supposed to be the seat of all vital func- tions, and the other, the micronucleus, which controls the reproduction. The Paramoecium reproduces by fission, both nuclei being divided, but conjugation also is manifested. In conjugation, two Paramcecia unite temporarily, ex- change a portion of the micronuclei, and perform other processes; they then separate, and continue more actively the process of transverse division or fission. Fig. 2.—Parame- cium caudatum, from the ventral side, show- ing the vestibule en face; arrows inside the body indicate the di- rection of protoplasmic currents; those outside, the direction of water currents caused by the cilia. c.v, Contractile vacuoles; f.v, food vac- uoles; w.v, water vacu- oles; m, mouth; mac, macronucleus; mic, mi- cronucleus; @, esopha- gus; v, vestibule. . The anterior end is directed upward. (Sedgwick and Wilson.) While these examples are only a few of the thousands of species and of the countless myriads of individuals of proto- zoans, yet, if carefully studied, they teach many things. 6 BRANCH PROTOZOA Fig. 3.—Organisms very abundantly found in common sea-water that has stood a few days in an open shallow dish: a, Acineta with embryo budding off; 6, resting spores of alga, with bacteria; c, Chilodon; d, small Navicula; c, Cocconeis; f, larger species of Navicula; g, heliozoan, with two entrapped infusoria; h, germinating alga cells; 7, small colony of bac- teria in zo6glea stage with small flagellate infusoria near by; hk, flagellate infusorian; m, infusorian Mesodinium; n, ciliate infusorian; v, Vorticella, with small portion of its stalk. (Bull. U.S. F. C., 1895.) INFUSORIA 7) Protoplasm.—Living protoplasm is the active substance of all living organisms. All the forces or conditions which tend to cause response or reaction in living protoplasm are called stimuli. The principal stimuli! may be classed as chemical stimuli, differences in temperature, light, contact, electricity, and gravity. Protozoans possess: (1) Irritability, that property of living protoplasm which gives it power to respond to stimuli; (2) automatism, the power of movement, or of changing the form. Locomotion.—Protozoans move by means of pseudopodia, cilia, or flagella. Some forms, as the Vorticel’la, are fixed, and can move only by the contractility of their stalks or stems. Nutrition—The food of protozoans is composed of whatever minute organisms or fragments of organic matter they are able to obtain in the water. The parasitic forms, of course, simply absorb nutriment from the liquids of the host. The proc- ess of nutrition in the simplest protozoan consists In wrapping or, more correctly, flowing itself about the particle of food, absorbing the nutriment needed, and rejecting what it cannot use. Thus we see that it has the power of selective absorption, or digestion. Circulation is brought about by simply changing the form of the body mass, thus changing the position of the absorbed nutriment in the one-celled body. Assimilation, or the making of this absorbed material into Its own body substance, next takes place, and, as a consequence, growth. The using up of assimilated material for heat or motion (energy), or metabolism, also takes place. 1'The reactions (orientation) of animals in response to these various stimuli are called tropisms; the response to chemical stimuli is called chemotropism; to heat, thermotropism; to light, phototropism; to contact, thigmotropism; to electricity, electrotropism; to gravity, geotropism, and so on. Loeb and others claim that the movements of the lower forms and many of those of the higher forms are purely physical and chemical reac- tions, just exactly as those known to us in the inorganic world. H. S. Jennings, who is another very careful investigator, asserts that his inves- tigations show “‘ that in these creatures their behavior is not, as a rule, on the tropism plan—a set, forced method of reacting to each particular agent —but takes place in a much more flexible, less directly, machine-like way by the method of trial and error. . . . This method leads upward, offer- Ing at every point opportunity for development, and showing even in the unicellular organisms what must be considered the beginnings of intelli- gence and of many other qualities found in higher animals.” 8 _ BRANCH PROTOZOA Respiration, or the taking in of oxygen and the giving off of carbonic acid gas and other wastes, is effected by the absorb- tion of the one and the throwing off of the other through the surface. Excretion takes place through the surface or through the contractile vacuole, there being a definite point at which the waste is ejected in the more advanced forms, such as the Paramecium and the Vorticella. Multiplication—While these life processes are going on, the animal grows or increases in size. This size must necessarily be very limited, for only small animals could live in this primi- tive way; hence, when the protozoan has reached a sufficient size, it divides into two complete halves, each half containing its share of the original cell-nucleus, as well as of the cytoplasm or protoplasmic cell body. This cell division, or the multiplica- tion of individuals, is called fission. After simple fission has taken place for many generations the fusion of two individuals, or conjugation, in which the nucleus of one individual is broken up and fused with that of the other, occurs. After this fusion, the process of fission continues, in which each new individual now contains a portion of the two parent nuclei which were fused in conjugation, instead of one parent nucleus as before con- jugation. This surely contains a suggestion of sexual mul- tiplication, though the conjugating cells may appear exactly alike. However, instances are given in which the individuals differ in size, the ‘ males” being smaller and more mobile. Also we see, not exactly “ alternation of generations,” but, at any rate, alternation of methods of reproduction. Animal Mind.'—Of the mental life of the protozoan little is known. If the rudiments of future complex animals is fore- shadowed in the protozoan, why may we not recognize the fact that here, too, is found the merest suggestion of the mental life as well? It has been abundantly demonstrated that protozoans possess trritability and contractility. It has been shown that they are sensitive to touch or contact, and, indeed, can discriminate 1 Mind is here used in the biologic sense, and is the “sum total of all psychic changes, actions, and reactions.”’—Jordan and Kellogg’s ‘“ Evolu- tion and Animal Life,” p. 448. INFUSORIA 9 between a hard substance and a softer substance suitable for food, as well as to recognize their kind by contact. Weir, in his ‘‘ Dawn of Reason,” tells of observations with an Actinoph’rys, in which it was seen to discriminate between starch grains and uric-acid crystals. Protozoans are also known to be responsive to heat and light. Weir also states as his opinion that all animals can distinguish day from night. The question remains as to whether or not this is ascertained by sight. However this may be, there can be absolutely no vision, because there is no mechanism for it. Importance of Protozoans.—(1) They furnish, either directly or indirectly, food for all higher forms of life. (2) They are scavengers of decayed organic matter. (3) By their countless numbers throughout the ages, vast formations of chalk or lime- stone have been made. Myriads of them are still sinking to the bottom of the ocean as Globigeri’na ooze or feadiolarian ooze. Since these animals are aquatic, geologists know that wherever these vast formations are found, there was once the sea. (4) Some of them are parasitic in the lower animals and in man, causing diseases which are ofttimes widespread and serious.’ Classification (Adapted from Parker and Haswell): Class. Examples. I. Rhizdp’oda. Amee’ba, ete. II. Mastigdph’ora. Euglé’na, Vol’vox. III. Sporozd’/a. Grégari’na, ete. IV. Infuso’ria. Paramce’cium and Vorticél’la. 1 Colonial Protozoa. See Jordan’s “Evolution and Animal Life,” p. 217. BRANCH PORIFERA ALL animals except the Protozoans are multicellular and are classed as Metazoa. Differentiation.—In all we find, to a greater or less degree, dwision of labor among the cells, or the differentiation into tissues and organs for special functions. Reproduction.—True sexual reproduction is the characteristic method among Metazoans. Porifera.—These aquatic, many-celled animals were formerly considered as plants. Indeed, they look like seaweeds among the rocks at the bottom of the sea. Most of the sponges are marine, but there are a number of fresh-water forms. Fresh-water sponges are widely distributed, and are attached to weeds or submerged objects along the margins of clear springs or ponds. Sponges vary in color from a greenish hue to red, brown, or flesh color. All of the soft parts, as well as the skin or covering, is gone from the commercial sponges. Their shape, as is seen in the sponges of commerce, is irregu- lar even in the same species; it varies with the environment, In order that the sponges may adapt themselves to the surface to which they are attached or the depth and currents of the water. Their size varies from a fraction of an inch to two or three feet in diameter. Structure-—The body of the Porifera consists of many cells arranged in two layers, an inner, or endoderm, and an outer, or ectoderm. There is a middle undifferentiated layer (mesoglea). The simplest sponge is cylindric or vase shaped (Fig. 4), while others, more complicated, consist of a system of branch- ing tubes. At the free end of each is a small opening, the osculum, or exhalant orifice, while the walls of the cylinder are perforated by exceedingly minute inhalant pores. The ecto- derm consists of flattened cells, which are also found to extend for a short distance inside the osculum, while the rest of the tube 10 MULTIPLICATION ial is lined with a single layer of peculiarly shaped columnar cells, each possessing a flagellum. The skeleton is developed in the middle layer and may consist of silicious or of calcareous spicules of a great variety of form, sometimes they are anchor shaped, and again others are club shaped, spear shaped, or cruciform. The so-called glass _ sponges sometimes have beautiful silici- _ ous skeletons. In other cases the skele- ton consists simply of fine, flexible, mter- woven fibers of tough, horny spongin. It is the skeleton, denuded of the flesh, or sarcode, that covers it in life, which forms the commercial sponge. A few sponges have no skeletons. Nutrition—There are no organs of digestion, circulation, or respiration in the sponge. The food consists of micro- scopic plants or animals, or of minute particles of organic matter floating in the water. The food-laden water enters through the inhalant pores and is carried by the movement of the flagella through the canals or paragastric cavities. The food as well as oxygen is taken up by the cells lining the canals and by the ameboid cells. The waste is carried out by the outgoing currents of water, which (bere nt empty through the osculum, or, if the Fig. 4—A simple sponge is complex, the oscula. sponge (Calcolynthus _ Locomotion.—At first the larval sponge sere fee is free swimming, by means of cilia. (After Hickel.) It soon becomes fixed to some stone or other object or animal, and assumes the fixed ways of its ancestors. Multiplication—(1) Asexual, by external budding and the consequent formation of a united colony, or by internal gem- mules; (2) sexual, thus insuring the perpetuation of the species. Sponges are hermaphroditic, that is, both the male elements 2 BRANCH PORIFERA (sperm cells) and the female elements or eggs (ova) are con- tained in the same individual (Fig. 5). It is from the union of a sperm cell with an ovum that the new individual sponge is developed. The sperm cells and the ova rarely mature at the same time in the same individual. Hence, the ova in the canals of one sponge are fertilized by the spermatozoa of an- other sponge, which are carried to them by the afferent currents of water in the canals, thus insuring cross-fertilization. The eges are retained in the canals until the blastula stage of their Fig. 5.—First stages in embryonic development of the pond snail (Lymneus): a, Egg cell; 6, first cleavage; c, second cleavage; d, third cleay- age; e, after numerous cleavages (Morula); f, blastula (in section); g, gastrula just forming (in section); h, gastrula completed (in section). (After Rabl.) This may be taken as a type of the earliest development of all many celled animals (Metazoa). (From Jordan and Kellogg, “ Animal Life,” D. Appleton and Co., Publishers.) development is reached, then they are set free and pass out at the exhalant opening or osculum. The fresh-water sponges (spongilla) bear small, seed-like bodies called gemmules toward the approach of winter. The parent sponge dies, the gemmules remain dormant until the next spring, when the rising temperature calls them to renewed life. They grow into mature spongilla, bear other gemmules, and thus the life- history of their race is repeated. Animal Mind.—Sponges have no well-marked nerve-cells, though the simplest elements of both nerve and muscle have been PROTECTIVE RESEMBLANCE 13 described as belonging to them. It is evident that the sponge possesses irritability and contractility. It has the instincts of self-preservation and of the perpetuation of its species. No one can. correctly interpret the psychologic phenomena of any animal until he has passed through the same psychic phenomena as that animal, and then become a man with the memory of these experiences and what they signified to that animal. Since we cannot do that, we must be content to infer the significance _of certain biologic phenomena from comparison with our own experiences. Environment.—As has been said, sponges are greatly in- fluenced as to their shape by the objects to which they are at- Fig. 6.—A young sponge. (After Burnet.) tached and by the depth and currents of the water. They are much more nearly uniform in deeper waters. The plastic sponge well illustrates the influence of gravity (geotropism) upon an animal. It also shows rheotropism.' Protective Resemblance.—Their protective resemblance is exceedingly good. They look so much like the seaweed and other aquatic vegetation that they are well concealed from ‘the animals which prey upon them, such as worms, crustaceans, mollusks, and other marine invertebrates. Their tough, horny texture and their silicious or calcareous spicules are also a means of protection. Their characteristic odor, said to re- semble garlic, makes them distasteful to fishes. 1 See Glossary. 14 BRANCH PORIFERA Symbiosis.—Examples of symbiosis are found among them, as that of the sponge and the crab. The sponge attached to the crab is carried about by it and given better opportunity of ob- taining food and oxygen, while the crab, in turn, is concealed from its enemies by the sponge. In the fresh-water sponge, a green alga sometimes grows, giving the green color to the mass. Various small marine forms are found in the sponges, giving good examples of commensalism. Sponges are never parasitic. Fig. 7.—Spongers at work. The “sponge hook” is a three-toothed curved hook attached to a pole, the length of which varies with the depth of the water. The sponge-glass is a common water-pail with the bottom knocked out and a pane of window glass put in its place. It is used for seeing below the surface where the water is disturbed by ripples. (Cobb, in Circular 535, U.S. F. C., 1902.) Use.—They are of use as food for other animals, and their skeletons form a very useful article of commerce. The sponges of shallow water are obtained by men in boats, with a dredge or a long-handled hook or rake (Fig. 7); those of the deeper waters, by divers. They are then exposed to the air for a time and then heaped up in water again in tanks CLASSIFICATION 15 provided for them, where they decay. The animal matter in them is ‘ beaten, squeezed, or washed out,” and their skeletons sent to market (Fig. 9). Geographic Distribution.—Fresh-water sponges are found in streams and lakes in all the continents. Marine forms are found in all seas and in all depths, from the shore between tide-marks to the deepest abysses of the ocean. ‘They are most abundant in tropical waters. _ Geologic Distribution.—Silicious sponges were not uncommon in the Cambrian Period, and are found in the formations from bin Fig. 8—Bringing sponges from the vessels to sponge wharf at Key West. (Report U.S. F. C., 1902.) that time on. They were abundant in the Jurassic and very abundant in the Cretaceous of Europe; none have been found in that of America. Important Biologic Facts.—Even in this low type there is a differentiation of certain cells for certain purposes, as the skeletal and reproductive cells. True sexual reproduction ap- pears for the first time in the Porifera. Conjugation was noted in the Paramcecium. Classification.—Sponges are of three kinds: (1) The calcar- eous sponges, containing much lime. They are of little or 16 BRANCH PORIFERA no commercial value. Example, Grantia. (2) The silicious sponges, in which the skeleton is largely silica. Example, Euplectel'la. (3) The horny sponges of commerce. Euspongia group. To this group belong the half-dozen species of Florida and the Mediterranean and the Red Seas. Our American sup- ply comes principally from Florida and the Mediterranean Sea = sya Fig. 9.—A sponge auction at Anclote. (Report U.S. F. C., 1902). from water not exceeding 30 fathoms deep. Examples of this group are Spongia, and the fresh-water forms of the genus Spongilla. Most zodlogists make but one class of porifera; others, two classes: I. Calca’rea. Il. Non-calea’rea. BRANCH CQiLENTERATA ‘Tuis branch comprises our fresh-water Hydra, and a few allies, and the marine forms, jelly-fishes, corals, and sea-ane- mones. This branch finds representatives from the shore line and the surface to the profound depths of the ocean. ' The body, which is usually radially symmetric, consists es- sentially of a two-layered sac, which is open at one end and closed at the other, and in which there is a simple or branched gastric cavity. The outer layer is called the ectoderm; the inner layer, the endoderm, and a gelatinous non-cellular layer between them, the mesoglea. Some ccelenterates are soft- bodied, others secrete a calcareous or limy substance called coral. Around the free open end of the sac-like body are a varying number of tentacles. Nettle Cells.—Stinging or nettle cells are characteristic of this branch, except in Cetenoph’ora, where they are replaced by adhesive cells. These stinging cells, which are especially abundant on the tentacles, contain a fluid, and a spirally wound thread provided with barbs, which, when the animal is disturbed, are discharged into the body of the intruder, paralyzing it. It is then seized by the tentacles and drawn into the mouth. Size.—Ccelenterates vary in size from the little fresh-water hydra, a fraction of an inch in length and of the diameter of a pin, to the giant jelly-fishes, as the Cya’nea, which sometimes reach 7 or 8 feet in diameter and have tentacles more than 100 feet long. Locomotion.—Some members of this branch are free, as the jelly-fishes; some are permanently fixed; as the Corals, while some, as the Hydras, are temporarily fixed, moving from one position only to adhere to another, and thus making slow pro- gression. Multiplication is both sexual (by eggs) and asexual (by budding). Origin.—They are of ancient origin, being abundant in the Cambrian Period. 2 . 17 18 BRANCH CQ@LENTERATA CLASS I. HYDROZOA In this class are found the worldwide fresh-water Hydras and the marine Hydroid Colonies, such as Campanula’ria or Obe'lia. The Hydras are small fresh-water Hydrozo’a from 4 to 1 or possibly 3 inch in length. They may be white or colorless, or green or brown. The body is a simple cylinder (Fig. 10) or sac, closed at one end, and near the other surrounded by six or eight tentacles, Fig. 10.—Hydra: Longitudinal section of animal, showing m, mouth; t, tentacle; d, digestive cavity; b, bud; s, spermary; 0, ovary; ec, ectoderm; en, endoderm. Magnified. (From Dodge’s “‘ General Zodlogy,’”’ American Book Co., Publishers.) above which is the conical hypostome, at the apex of which is the mouth. The muscular fibers of the ectoderm extend lengthwise, while those of the endoderm extend around the body.! If disturbed, the Hydras protect themselves by withdrawing into a tiny sphere, while the tentacles contract until they look like so many small buds. The endoderm has flagellate cells lining the gastrovascular cavity. 1 Hertwig’s “Manual of Zodlogy,”’ Kingsley, p. 230. HYDROZOA 19 The food is obtained by the viscid tentacles, which, when the Hydra is undisturbed, are extended (as is usually the body), ready to grasp the prey, for this tiny animal is carnivorous, feeding upon small organisms, usually crustaceans. There are nettle cells, or nematocysts, in the ectoderm of the tentacles. When an animal comes in contact with a tentacle, the nemato- cysts near the point touched throw out stinging threads which partially paralyze the animal by the fluid which they discharge into the wound they have pierced. The tentacles then pass the prey to the mouth, which opens into the gastrovascular cavity, in which digestion is carried on and into which the wastes are gathered and thrown out through the only opening, the mouth. The Hydra, by its wide-open mouth and envelop- ing lips, often takes in organisms much larger than itself. Nerve-cells, sex-cells, and nettle-cells are situated in the ectoderm. Multiplication in the Hydra is both sexual and asexual. It reproduces by budding, but as the buds mature they become ' detached, so that no permanent colony is formed. It also reproduces by eggs, the animal being hermaphroditic, that is, the reproductive organs of both sexes are found in the same indi- vidual. Near the base of the tentacles are found the spermaries from which the sperm cells are discharged into the water; the ovaries are situated farther down, near the lower end of the body. The eggs are cross-fertilized, that? is, fertilized by the sperm cells of another individual. After fertilization the ova remain in the ectoderm for some time, when they become en- cysted in spiny cysts, drop off into the water, and sink to the bottom. They lie here till the following spring, when they break their casing and come forth as minute Hydras. In the encysted condition they are able to withstand cold and drouth, thus insuring the perpetuation of the species. Hydras also have the power of regenerating the whole body from a part in case of injury. Locomotion.—The Hydra is temporarily fixed by adhering to the submerged stems of water plants by means of a sticky secretion from the closed end of the tube. It can detach itself, and, by grasping with its tentacles, can pull itself up and again attach the end of its tubular body to an object. By this cater- 20 BRANCH CQGSLENTERATA pillar-like looping it is able to change its position or perform slight locomotion. Dispersal— While the mature Hydra has very limited powers of locomotion, or direct dispersal, its offspring may be widely Fig. 11.—A, Part of the colony of Bougainvil’lea mus'cus, one of the com- pound Hydrozoa, of the natural size. B, Part of the same enlarged: p, A polypite fully expanded; m, an incompletely developed reproductive bud; m', a more completely developed reproductive bud; f, ccoenosare with its investing periderm and central canal. C, A free reproductive bud or medu- siform gonophore of the same: n, Gonocalyx; p, manubrium; c, one of the radiating gastrovascular canals; 0, ocellus; v, velum; ¢t, tentacle. (After Allman.) separated from the parent through indirect dispersal, or the drifting about of the encysted eggs by means of currents and HYDROZOA Zl waves, or the transporting, by the same means, of the débris to which they are attached in later life. Symbiosis is exemplified by Hyd'ra vir’idis, or the green Hydra, the color probably being due to the presence of small green alge. Another species found in Russia, Polypo’dvum hydrifor'me, of which little is known, is parasitic on sturgeon eggs.’ A Hydroid Colony (Fig. 11).—Suppose a hydra-like animal to bud and branch until it looked like a ty bushy shrub. This will give you some idea of these plant-like hydroids. These hydra-like animals, or polyps, are connected by a system of tubes, the common stem or axis bearing many individual zoéids. A ff Fig. 12.—Obe’lia flabella'ta. (Hincks.) Fig. 13.—Obe'lia commissura'lis. Obelia (Figs. 12, 13) is a good representative of such colonies. The axis is made up of a creeping horizontal portion and of vertical axes. The short, alternate, lateral branches of these axes bear zodids at their extremities, or, again branching, the polyps or zodids are borne on the second set of branches. When these zodids are immature, they are little, club-shaped enlarge- ments. When mature, the polyps are surrounded proximally by a little glassy, protective cup, the hydrotheca, and distally bear about a score of tentacles. These are the nutritive zodéids, for division of labor is found here. The tentacle-bearing indi- viduals procure the food, and since the tubes are all hollow 1 Hertwig’s ‘‘ Manual of Zodlogy,” Kingsley, p. 241. De, BRANCH CQ@LENTERATA and connected, the whole colony shares the food thus supplied. When disturbed the polyp withdraws into the hydrotheca for protection. Blastostyles.——But while the majority of the members of this colony are hydra-like, tentacle-bearing polyps which reproduce by budding only, and can enlarge the original colony, they have no power of directly producing a new colony in a more favorable position. There is, therefore, another set of individ- uals (see Fig. 11). These, while forming a part of this tubular colony, are modified in their form for a particular function. They are situated toward the proximal region of the colony and are long, cylindric bodies, known as blastostyles, each of which is enclosed in a transparent case, the gonotheca. ‘These are the reproductive zodids, and bear small lateral circular buds called medusa buds, which, as they mature, become detached and pass out through an opening now formed at the end of the gonotheca. Alternation of Generations.—These medusa buds are sexual and diecious, i. e., the sexes are separate, one individual producing the ova and another the sperm cells. -After fertilization, which takes place in the water, the egg develops into a simple, free- swimming ciliated larva, the planula, which soon attaches itself to some object, develops into a polyp, and, by budding, forms a new colony. This regular reproduction by budding, and then by eggs, and then by budding again is called alternation of genera- tions, or metagenesis. Meduse.—Careful study shows that the Medusa is only a highly developed or modified zodid. The cylindric body has been developed into a disk or umbrella-shaped body (Fig. 14); the long axis has been greatly shortened and is suspended be- neath the center of the sub-umbrella, as the under surface of the disk is called, where it takes the name of manubriwm, or “handle.” At the free end of this manubrium is the mouth, which opens into the gastric cavity that occupies the whole interior of the handle. At the base of the manubrium four radial canals, equally distant from each other, are sent out to the circular canal, which runs around the margin of the umbrella, but within its substance. Thus, the food taken into the mouth is distributed to the whole animal. The whole canal system is lined by endo- HYDROZOA Dey derm, which is ciliated. The endoderm also forms the axes of the tentacles. There is also a layer of endoderm between the radial canals extending from the circular canal to the gastric cavity. Between the endoderm and the ectoderm, which covers the convex surface or ex-umbrella, is a much-thickened jelly-like mass of the mesoglea, while between the endoderm and the ectoderm covering the sub-umbrella there is a thin layer of mesoglea. The ectoderm, of course, covers the tenta- cles, where it is well supplied with stinging cells. At the margin the ectoderm of both the sub- and ex-umbrellas forms a narrow Fig. 14.—1, Pela’gia panopy’ra, oral view of mature medusa. 2. The same, side view. (Mayer, i in Bull. U.S. F. C., 1903.) fold or shelf, the velwm, which hangs down when at rest, but draws up like a diaphragm across the bottom of the umbrella when the bell contracts. By the forcing out of the water the animal is forced forward, and so locomotion is effected. Around the outside of the velum is a row of tentacles, usually four or some multiple of four in number. Muscles of a longitudinal character control the tentacles, while circular striped muscles surround the sub-umbrella and velum, and, by contracting the umbrella and velum, produce locomotion. 24 BRANCH CQ2LENTERATA The nerve ring surrounds the margin between the circular muscles of the umbrella and those of the velum. At the bases of two of the tentacles of each quadrant there are sense organs. They probably aid the medusa in determining in what direction, with regard to the vertical, it is swimming, that is, whether it is moving up, down, or sidewise. In other medusz the simplest of eyes, red pigment spots, which may or may not have a lens, are found. The food of the medusa consists of both plants and animals. It is very voracious and grows rapidly after leaving the colony. WW ANN ) \ \" ne cy @. ic b Fig. 15.— Hydractin'ia polycli’na: a, Nutritive individual; b, reproduc- tive individual; c, spiral zodids or fighting individuals. (Bull. 455, U.S. 19, (Gs Multiplication After a time either eggs or sperm cells develop, and are set free in the water, where they unite with those of some other medusa and develop into the tiny larval form, which soon attaches itself and grows into a hydroid, to bud and branch and produce again the medusez, thus repeating the life-cycle and the reproduction by alternation of genera- tions. There are more than a thousand species of the class Hydrozoa. In some forms (Fig. 15), as the Hy’dractin’ia, there are several classes of _ individuals—the nutritive, the defensive, and the reproductive—with HYDROZOA rots the corresponding division of labor. These Hydractin’ia live upon the surface of the shells of sea-snails or whelks, which are inhabited by hermit crabs, and afford another good example of symbiosis. The Hydractinia gets free transportation, aiding it in secur- ing food; it also probably feeds upon minute fragments of the crab’s food; while the crab, in turn, is protected from intruders by the stinging cells of the Hydractinia. If the hydroids are in any way torn from the shell, the crab finds another colony, and, tearing it loose from its supporting object, places it upon its borrowed shell. Millep'ora alcicor’nis is a species of so-called hydroid ‘‘ corals’’—the beau- tiful elk-horn or stag-horn coral of Florida. The permanent colony num- bers thousands of individuals, which differ in their structure according to their division of labor. Their cal- careous skeletons are a cuticular prod- uct of the ectoderm. Another order of the class of Hydrozoa is characterized by a closed float containing air or gas which serves to keep the colony vertical in the water. In the “ Portuguese man-of-war ”’ (Fig. 16), found as far north as New England, there are suspended from the large float (3 to 12 cm.)! peacock blue, or, in some cases, orange in color, several kinds of individuals; some of them, many feet in length and armed with nettle cells, capture the food and bear it to the mouth-bearing or nutritive polyps, which digest the food and distribute it to the col- Sn MAP Yel ler a oS \ Ry SS wt Fig. 16.—A Portuguese man= of-war (Physalia), with man-of- war fishes (Nomeus gronovit) liv- ing in the shelter of the stinging feelers. Specimens from _ off Tampa, Fla. (From Jordan and Kellogg, ‘“‘ Animal Life,” OD. Appleton and Co., Publishers.) ony. Others, the feelers, are groups of deep blue medusoids re- sembling bunches of grapes, while others, with swimming move- ments, aided by the wind, drive the colony from place to place. 1 Parker and Haswell. 26 BRANCH CQSLENTERATA CLASS II. THE SCYPHOZO’A Jelly-fishes are soft umbrella-like creatures resembling molds of jelly or gelatin, as one sees who picks them up along the beach, where they have been cast ashore by the waves. Their tissues are very watery, hence the scarcity of their fossil remains. However, very perfect impressions of jelly-fishes are found in the upper Jurassic Period. Most jelly-fishes are marine and free swimming, though a few are temporarily attached. They are most abundant in the tropics. Great schools of them are sometimes seen. Sometimes they are phosphorescent. They vary in size from about 4 mm., in the simple little, bell-like Tessera, to 1 foot in the Aurelia, and 7 or 8 feet in diameter in the Cyanea, whose tentacles sometimes reach the length of 130 feet. A small form, Gonionemus, found at Wood’s Holl, Mass., is green and about 1 inch in diameter. It grows on eel- grass. All are carnivorous, feeding mostly upon crustaceans, though some of the larger ones capture fishes of considerable size. The food is captured by the tentacles, which are suspended from the margin of the umbrella and which are armed with stinging thread cells. Locomotion is effected by the flapping of the umbrella-like body, there being usually no velum. Minute colored “ eye-specks”’ are around the rim. Multiplication usually is by alternation of generations, but the young medusa or ephyra, as it is called, undergoes a meta- morphosis or change of form as it matures. In some cases the egg develops directly into the larval medusa and there is no alternation of generations, but simple metamorphosis. CLASS III. ACTINOZO’A This class includes sea-anemones, sea-pens, and corals. Only the polyp form is found in this class, no medusa being known among them. They are exclusively marine. They are usually fixed and many form permanent colonies. One point in their development is a step in advance of the Hydrozoa, 2. e., the development of a gullet, esophagus, or stomodeum, the beginning of which is seen in the Seyphozoa. The hypostome, which in Hydrozoa bore the mouth at its apex, ACTINOZOA rae is here inflected and forms a tube dipping down into the body cavity, but not reaching the bottom of it. The lower end of this tube or esophagus (which is really the beginning of the ali- mentary tube of higher animals) corresponds to the mouth of the Hydra, so that the tube is lined with ectoderm. The mouth is the only external organ, and serves both for the entrance of food and the ejection of waste. The body cavity about this tube is divided by thin partitions into radiating spaces. _ No actinozoan is microscopic. All are long lived. One in an English aquarium lived more than sixty years.' The sea-ane- mones and all true corals producing reefs and islands have the number of their tentacles in multiples of six. SS Z SSs YZ SSS 7 =A =~ We We TED. S ; UGH We = GA Fig. 17.—Sea-anemone (Metrid’ium). (Emerton.) The Sea-anemones (Fig. 17).—As one gazes in wonder at the sea-anemones in their marine home, he can scarcely persuade himself that those beautifully colored objects, so flower-lhke— hollow cups with their petals and sepals of such wonderful tints —are else than flowers. But he touches one, the “ sepals and petals ” close in upon his fingers, they tingle, and he finds that this flower-like object is an animal and that the “‘ sepals and petals’ are tentacles. A very different appearance it makes when the body has been drawn down close to its attachment by the longitudinal muscles, while the circular muscles shut in the 1‘*General Zodlogy,’’ Dodge, p. 75. 28 BRANCH CCQALENTERATA Fig. 18.—Athe'lia mirab'ilis. General view of branch. View of a calice. (Vaughan, in Bull. U.S. F. C., 1900.) Fig. 19.—Favia fragum (Esper). View of a corallum from the side. (Vaughan, in Bull. U.S. F. C., 1900.) retracted tentacles until it looks like a round mass of flesh. The tentacles are hollow and are armed with lasso cells, which are ACTINOZOA 29 useful not only for defense, but for capturing crabs and small fishes which form the anemone’s food. Sea-anemones are solitary, that is, they form no permanent colony. They have no true skeleton. There is no alternation of generations. They vary in size from § inch to 2 feet in diameter, and, though attached, have the power of changing their position. The Stony Corals (Fig. 18).—The coral polyps resemble small sea-anemones on a much-branched stem. The calcareous skele- Fig. 20.—Isopo'ra murica'ta forma prolifera lam. "nd of branch, height 9em. (Vaughan, U.S. F. C. Bull., 1900.) ton is secreted by the ectoderm. The branched form arises from the continual budding and branching from a parent stem. The different forms (Fig. 19) of coral are caused by the different modes of budding in the various species. Corals are of various colors and some are said to be phosphorescent. The members of a coral colony are organically connected. Each feeds himself, it is true, but no individual of the colony is independent of the others. The size varies from that of the head of a pin to inch, RATA LENTE 101) 1 BRANCH C 2A) ter. lame d in f 1 foot These myriads of coral polyps (Fig. 20) secrete great quanti- ties of lime, the waves break off the branches the solitary mushroom coral being sometimes of the exceptional s1Ze O 1 them up, , grinc Bae aan These are confined to warm regions it Te a ae caren bes mix them with sand and shells, and thus build up coral reefs and islands of vast extent. fan. a A se ‘je, 21.— ce coral colonies in iS) ) de of the equator i ') ch about 30 degrees on ea ey tS) S508 ESF: fe) eS Gel S| =| Cres me M4 S 6 S| © SS tee ee (aD) aSHF SSO a=) Se Ss 63 0 sor 2 re Som & epee Sma 72 8 & ice LS ss =) 7 Gu Ss Bp SE iS) aj Bee ce ESL eS DS ap so =) fs “SI eee we Moa ee See ae ane SRBC 5 A femes £ ao eae N Coe a 2+ S = & w o— Sus Se Aa) 2 Sia Saad they cannot live at the mouth of a river. 1 Scott’s ‘ Geology.” CTENOPHORA 31 The Octocoral’la, or those forms which have eight tentacles, are found in all seas, both in shallow water and at great depths. They include the organ-pipe coral, the precious red coral (Corallium rubrum) of the Medi- terranean Sea, and the sea-pens and the sea-fans. The mesoglea of many octocoralla contains irregular calcareous spicules. The sea-pens (Pennatula’cea) usually form an elongated colony. The stem, one end of which is embedded in the sand or mud of the sea bottom, is supported by a calcareous or horny skeleton. The distal portion is dis- tended like a feather and bears the dimorphic polyps. Fig. 22.—Photograph taken with the camera submerged,. to show aquatic animals in their natural environment. In the background are seen sea-fan and branching gorgonian. (Bull. U.S. B. F., 1907.) The sea-fans (Gorgona’cea) (Fig. 21) havea branched colonial axis formed of horny or calcareous substance from the ectoderm, with spicules in the mesoglea. In some cases the skeleton formed by the spicules forms a branched axis, as in Coralliwm rubrum, or it may form a “ series of connected tubes for the individual, as in the organ-pipe coral (T'ubip’ora).” ‘The red coral is found only in the Mediterranean Sea at a depth of from 10 to 20 fathoms.’ CLASS IV. CTENOPHORA The Cténédph’ora, or ‘ comb-jellies,’ are so-called from eight bands of comb-like cilia fused at their bases, which sur- round their nearly transparent bodies. The body is non-con- 1 Parker and Haswell’s ‘‘Zodélogy.” 32 BRANCH CQRLENTERATA tractile, and these cilia accomplish locomotion. They are free and single, there being no polyp stage. They are found from the tropical to the arctic seas. They are small—from 5 to 20 mm. in diameter—and their shape varies from that of a pear to a sac-like or ribbon-like form. They have but two tentacles. They are hermaphroditic, multiplying by eggs. The central nervous system is represented by a ciliated area on the aboral pole, and is connected with a single sensory organ. Economic Value.—The animals of this branch are of great use to man, indirectly, by furnishing food for other animals, and, directly, by the formation of great beds of limestone and of coral reefs and islands, also by forming an article of commerce of no small value.! ‘The red coral of commerce is obtained in the Mediterranean Sea off the coast of Africa and the west coast of Italy. The price varies according to the color. The finest rose pink in large pieces is valued at $400 or more an ounce. The common article brings from $1 to $1.50 an ounce.’ Geologic Distribution—The hydrozoa are believed to be represented by the Graptolites, which appeared in the Cambrian Period, were numerous in the Ordovician, greatly diminished in the Silurian, and almost extinct in the Devonian. Large numbers of casts of jelly-fishes are found in the Cambrian rocks.’ Hydroids and true corals were important. Marine life and reefs were formed in the Silurian Period. Corals vastly increased in size and number in the Devonian Period, and were abundant in the Carboniferous, contributing largely to the limestone. Hydractinia were ‘oxcundl § in the Cretaceous Period. Important Biologic Facts.—In the Ctenophora is found for the first time a true middle layer of mesoderm cells.* In the hydroid colony is found the division of labor among the different sets of individual zodids and a differentiation of structure according to their function. 1“ The fishing for the red coral (Corallium rubrum) at Naples amounts yearly to half a million dollars.”—Kingsley. 2 Adam’s ‘‘Commercial Geography.” 3 Scott’s ‘‘ Geology,” p. 371. 4 Parker and Haswell’s ‘ Zoélogy,” vol. 1, p. 207. CTENOPHORA 33 Classification.— Class. Examples. I. Hydrozd’a. Hy’dra, Hydroid Colonies. Il. Se¥phozd’a. Jelly-fishes. Ill. Actinozd’a. Sea Anemones and Coral Polyps. IV. Cténdph’ora. ““ Comb-jellies.”’ 3 BRANCH PLATYHELMINTHES Platyhélmin’thes, or Flat Worms, have three germ layers, the ectoderm, the mesoderm, and the endoderm. They are flattened dorsoventrally and are bilaterally symmetric. They have no skeleton, no circulatory system, and no ccelom or body cavity. ‘They have an anterior and a posterior end, but rarely a distinct head. The nervous system is composed of superesophageal ganglia and lateral nerve-trunks. The excretory system consists of water-vascular tubes. There is no anal opening. Development is sometimes with and sometimes without a metamorphosis. Habitat—Some, as the liver-fluke and the tapeworm, are parasitic; others, as Planaria, live in fresh water. Some live in moist places or in the mud at the bottom of ponds and streams; while others, as Leptoplana, are marine. Size.—The parasitic forms are sometimes 30 or 40 feet in length, while the free forms are but 2 or 3 inches in length. These are often found under stones, and are exceedingly deli- cate. Protective resemblance is very great, in some species, while a few are nearly transparent. : CLASS I. TURBELLARIA The class Turbella’ria consists principally of non-parasitie forms which are ciliated externally. There is usually a diges- tive cavity. The prevailing shape is leaf-form, like that of Plana'ria. Some marine forms, however, are shaped like “a thin ribbon with puckered edges,” others may be thickened and band-like, as in the land planarians, while others approach the shape of a cylinder. Locomotion is performed by the fine vibratile cilia which cover the surface. The eetoderm contains sensory and gland-cells. 34 TREMATODA 35 CLASS II. TREMATODA The class Trématd’da is comprised of worms either internally or externally parasitic. { & Fig. 23.—The common liver-fluke (Fasci’ola hepat’ica) enlarged to show the anatomic characters: ac, Acetab- ulum;c, p., cirrus pouch; ?, intestinal ceca; m, mouth with oral sucker; ov, ovary; p. b., pharyngeal bulb; s. g., shell gland; ¢, profusely branched testicles; uf, uterus; va, vagina; v. g., profusely branched vitellogene gland. (After Stiles, 1894, p. 300.) The body is usually thicker than that of the turbellarians. The form is usually _ leaf-like, ‘though it is sometimes elon- gated. The anterior end is distinguished by the arrange- ment of suckers, and, in some of the external parasites, by eyes. | Fig. 24—Embryo of the com- mon liver-fluke (Fasciola hepatica) boring into a snail—x 370. (After Thomas, 1883, p. 285.) The suckers are organs of adhesion and are sometimes armed with bristles or hooks. They are also used in locomotion, which is a sort of looping, like that of the leech. Except in two cases the vibratile cilia are not found on the surface. — 36 BRANCH PLATYHELMINTHES The trematodes are hermaphroditic, and the development may be either with or without a metamorphosis. The Liver-fluke (Fig. 23) is parasitic in sheep. The eggs pass down the bile-ducts of the sheep into the intestine, and from there to the exterior, when the embryo escapes by the separating of the lid, or operculum, from the egg-shell. The ciliated larva swims about in the water or remains in the damp vegetation until it comes in contact with a pond or land snail (Fig. 24). It then bores into the body of the snail, where it develops into a_ sporocyst (Fig. 25), which produces redia. These redie possess a mouth, a pharynx, an intestine, and an opening for the escape of the young, which are internally produced. According to the season, these young are cercarie or redia, several generations of which may follow before the cercariw appear. The cercarie are adapted for aquatic life. Fig. 25.—Sporocyst of the com- Fig. 26.—Free-swimming cercaria mon liver-fluke from the body of a of the common liver-fluke, greatly snail, containing redie in course of enlarged. (After Leuckart.) development—enlarged 200 times. (After Leuckart.) The cercarie (Fig. 26) escape from the snail, swim about with their vibra- tile tails for a time, when the tails drop off and the cercarie become encysted on a plant. When this plant is eaten by a sheep, cow, or hog, the young escapes from the cyst and makes its way up the bile-ducts to the liver, where it develops into the mature worm and produces reproductive organs, thus completing the life-cycle. Sheep pastured in swampy places are likely to be infected by this para- site, and wet seasons cause epidemics. CESTODA ah In England the annual loss of sheep killed by the liver-flukes is estimated at $1,000,000, and it has been known to reach $3,000,000 in one year. There have been a few cases of this parasite found in man. CLASS III. CESTODA A tapeworm (Te’nia so’lium) is a parasite in the intestine of man. It is ribbon shaped (Fig. 27), beg much narrower at the attached end, the head, or scolezx. The scolex is knob-shaped and bears the organs of attach- ment, a circle of hooks at the end, and a sucking disk or cup- shaped sucker on each of the four sides. The attachment is temporary. Fig. 27.—Te'nia Bee (Eichhorst.) Segments.—The remainder of the tapeworm, except a short portion immediately posterior to the head, is made up of a series of segments or proglottides, the number of which varies in differ- ent species. In Teenia solium there are about eight hundred and fifty segments, while in the smaller species there are three or four hundred, and in the larger species, several thousand. These segments or proglottides are derived from the head by a kind of budding. Thus it is that so long as the head remains the tapeworm continues to grow. Digestion—There is no digestive system, the nutrition simply being absorbed from the liquids of the host. The nervous system consists of a pair of ganglia, from which two main nerve-cords extend back through the length of the worm. The excretory or water-vascular system consists usually of 38 BRANCH PLATYHELMINTHES four principal trunks extending throughout the scolex and proglottides. Multiplication and Development——Each proglottis, as it matures, becomes hermaphroditic. Since these proglottides are originally developed from the head, the posterior ones are * oldest. When filled with embryos, they are detached and pass out with the waste material from the intestine. When taken into the alimentary canal of the hog with its food, the hooked embryos bore through the intestinal wall and into the voluntary muscles, where they grow and continue to develop until they - {2 EOS BP RA x Fig. 28—Tenia echinococ’cus, en- Fig. 29.—Portion of the intestine larged. (Mosler and Peiper.) of a dog infested with echinococcus tapeworms, natural size. (Oster- tag.) reach the bladder-worm stage, or cysticercus. When pork containing a cysticercus is eaten, unless it has been killed by thorough cooking, the head is everted from the bladder-like covering and is attached to the intestinal wall of the host, where proglottides are rapidly developed. These mature in ten or twelve weeks. Species.—There are many species of tapeworms. One form, Tenia saginata, which occurs in man, is obtained through eating beef cooked rare; another form, Tenia solium,' already mentioned, from eating pork; and another, Bothrioceph’alus 1 Tenia solium is sometimes found in the encysted or intermediate stage in the muscles, eye, or brain of man. The eggs are thought to have been taken into the stomach with lettuce, cress, and the like, which had been watered with liquid manure. NEMERTINEA 39 latus, from eating fish. The latter species is the largest tape- worm found in man and sometimes reaches a length of 40 feet, and is composed of more than four thousand proglottides. It is rare in America, but is abundant in Russia, Switzerland, and the eastern provinces of Prussia. Another form (Fig. 28), perhaps the most formidable, is a small one, Tenia echinococ’cus, which lives, in the adult stage, in dogs (Fig. 29), and the eggs are easily taken into the human stomach by a person fondling and kissing infested dogs. The embryos (Fig. 30), when set Fig. 30.—Portion of hog’s liver infested with echinococcus bladder-worm. (Stiles. ) free, work their way into the liver, lungs, brain, or other organs, and produce tumors which sometimes reach a large size. Several species are found in domestic birds, one causing epidemics among chickens. A variety of Te’nia cenu’rus, in the brain of sheep, causes “staggers.” Rabbits, horses, cats, mice, and rats are also infested by tapeworms. CLASS IV. NEMERTINEA (Doubtful Platyhelminthes) The Nemertineans are most abundant in the mud or under stones along the seashore, only a few species living in fresh water. They differ from all other Platyhelminthes in having 40 . BRANCH PLATYHELMINTHES an alimentary tract with an anal opening and a distinct blood- vascular system.' They are usually dicecious.’ Geographic Distribution —This branch of animals is the most widely distributed of any above the protozoans. They are found on land, in streams, and in the depths of lake and sea. The parasitic forms are found in some stage in almost every class of metazoans, while others have a commensal life with ascidians. All are carnivorous. Economic Importance-—Many domestic animals are hosts for these parasites and much loss is occasioned thereby. A number of class Cestoda are parasitic in man and cause annoy- ing if not dangerous diseases. The only sure preventive of these parasites is to have all meats thoroughly cooked and fruits and vegetables well washed. Important Biologic Facts—-An anterior end—one placed foremost in locomotion—and a posterior end appear for the first time in platyhelminthes. Also right and left and dorsal and ventral sides are found. In the Nemertinea there is an alimentary tract with a mouth and an anal opening. There is no distinct ccelom. Class Turbellaria is the most primitive and the most closely related to the Ccelenterates, but it is not thought to be derived from them, though it shows special points of resemblance to the Ctenophora. It is thought that Trematoda and Cestoda are descendants of Turbellaria. In Trematoda is seen an alterna- tion of generations consisting of the succession of several dis- tinct generations in regular series. Such an alternation of gen- erations is termed heterogeny. The simple structure of parasitic forms illustrates the principle that easy life—one requiring little exertion—is accompanied by a low stage of development. Classification.— Class. Examples. I. Turbella/ria. Planarians. II. Trémato’da. Liver-fluke. III. Césto’da. Tapeworms. TV. Nemertin’ea. Carinella, Tetrastemma, etc. 1 McMurrich, p. 160; Osborn’s ‘‘ Economic Zoélogy,” p. 85; Kingsley’s | Hertwig, p. 289. 2 “ Invertebrate Zoélogy,” MeMurrich, p. 162; Parker and Haswell, p. 279. BRANCH NEMATHELMIN’THES Round- or Thread-worms.—The worms of this branch are elongated and cylindric and have a ccelom or body cavity. The vinegar-eel affords a good example. They differ from annelids in that they are not divided into segments or rings. CLASS I. NEMATODA The members of class Nématd’da are best known as para- sites, but there are many fresh-water and marine forms. The tough body wall encloses a body cavity which surrounds a straight alimentary tube having a terminal mouth and a ventral anal opening. An excretory system is usually present. The nervous system consists of an esophageal nerve ring which sends out six nerves anteriorly and six posteriorly. The only sense organs are sensory papille on the lips. The sexes are usually separate. Many of the aquatic forms are free. Some of the parasites infect plants, as Tylen’chus trit’/ici, which does great damage to wheat, and Heterode’ra schach’tii, to turnips in Europe. One form, Ascaris nigrovenosa,! living a parasitic life in the lungs of frogs and toads, is hermaphroditic. The embryos reach the alimentary canal and pass out with the waste material. In water they develop into a stage in which the sexes are separate. The eggs develop in the body of the female and devour the entire substance of the tissue of the mother, leaving only the cuticle. When set free they live in the mud until they are taken into the mouth of a frog, when they pass into the lungs and develop into the hermaphroditic stage. Here, again, is a peculiar alterna- tion of generations (heterogeny), the alternation of an hermaphroditic with a dioecious form. Trichinel’la spira’lis (Fig. 31) is another member of this class. In the adult stage it lives in the alimentary canal of man or of other mammals. The length of the adult male is about 7; inch, and that of the female about s Inch. The sexes are separate. The young, at least one thousand, are born alive. The young worms (Figs. 32, 33) pass through the intestinal wall and make their way to the voluntary muscles, where they penetrate the sarcolemma and become encysted. 1 Parker and Haswell, vol. i., p. 286. McMurrich, p. 176. 41 42 BRANCH NEMATHELMINTHES mi) pany ae ) Div) Bt mn ) ) Hh Dp} Fig. 32.—Larve of T'richinella spiralis im mus- cle, not yet encysted; enlarged. (Leuckart.) Fig. 33.—Piece of pork showing larve of Trichinella spiralis encysted in the muscle- fibers; natural size. (Ostertag.) Fig. 31.—Trichinella spiralis. Adult female, showing embryos, emb., in a uterus; gp., genital open- : ing through which the Sbvor = discharged; Fig. 34.—Enecysted larva of Trichinella spira- enlarged. (Leuckart.) lis; enlarged. (Leuckart.) NEMATODA 43 When the infested flesh, unless thoroughly cooked, is eaten by man the cysts are dissolved, the young entering the small intestine, the worms con- tinue developing and become sexually mature in a few days, the female penetrates into the superficial layer of the imtestinal villi, and in the course of a month gives birth to young, and then dies. The young wander through the lymph-vessels and blood-vessels into the capillaries, pass into the muscle and become encysted (Fig. 34), as did the parents in the former host; 1 ounce of infested pork, unless thoroughly cooked, may liberate 80,000 worms. If half of these were females, each producing 1000 embryos, 40,000,000 worms would shortly begin to migrate into the muscles, causing trichinosis, which may be fatal. The worst epidemic known was in Emmers Leben, Saxony, in 1884, where 364 persons were infected from eating one pig, and 57 persons died within a month. The Guinea-worm (Dracun/culus medinen/sis) is an East India parasite in the subcutaneous connective tissue of man. It is long and slender, sometimes 1 yard long. It forms abscesses under the skin. When the newborn young pass out of their host, if they pass into water, they enter the body of a small crustacean (the Cy- clops), which is necessary to their develop- - ment. It is supposed that they reach Gu the human system through the Cyclops, f which is swallowed in unfiltered drinking- water. A’ 0 +, v \| Fig. 35.—Eggs of the gape-worm Fig. 36.—Windpipe of chicken (Syn’gamus trachea/lis), one of them split open to show gape-worms at- hatching; enlarged 260 times. tached to its inner surface; en- (After Mégnin.) larged. (After Mégnin.) The hook-worm ( Neca’tor america’nus), of the Southern United States and the West Indies, is thought to have been introduced from Africa by macs “Tt is about { to 3 inch long and about as thick as a small hairpin.” —wtiles. “In hook-worm disease we have ground-itch, tibial ulcer, anemia, inter- ference with physical and mental development, and, in bad cases, dirt eating.” —Stitt, 244. Other Species.—There are various other species. Some, as the pin-worm . (Oxyuris vermicularis) and the round-worm (As/caris luwmbricoi'des), are parasitic in man. Some are parasitic in other mammals and some in birds. One of the latter, Syn’gamus trachea'lis (Fig. 35), about 4 inch in length, causes “‘gapes” in poultry (Fig. 36). 44 BRANCH NEMATHELMINTHES Gordius, the “ hair-worm,”’ is found in watering-troughs and erroneously believed by superstitious people or those ignorant of biologic principles to be horse hairs transformed into live worms.’ The larve are parasitic in the grasshopper, the adults live in water. Agassiz tells of experimenting with one 18 inches long which was wrapped in and out of its eggs, which were rolled up into a ball about the size of a coffee bean. He disentangled it and it ‘‘ sewed ”’ itself through and through the little white mass. Three times he separated the worm from its eggs, and each time the process of entangling was repeated, convincing Agassiz that there was a definite’ purpose in its attempts, and that even a being so low in the scale of animal existence has some dim consciousness of a relation to its offspring.t He placed a small portion of the egg mass under the microscope, and estimated that there were not less than 8,000,000 eggs in the whole mass, which, when unwound, made a string 12 feet long. CLASS II. ACANTHOCEPHALA Most of the class Acan’thocéph’ala are small parasites. The chief genus (Echinorhyn’chus) is parasitic in the intestines of mammals, birds, reptiles, amphibians, and fishes. The largest species is found in the pig, and one species, Hchinorhynchus hominis, is extremely rare in man. CLASS II. CHAXTOGNATHA This class contains but two genera of curious arrow-shaped worms, all but one species of which are pelagic. They are hermaphroditic and have three pairs of ccelomic pouches, ‘“‘ fins,”’ and bristle-like jaws. Economic Importance.—In this branch may be found worms which are harmful and those which are helpful to man. Those forms like Trichinella spiralis, which are parasitic In man, are very injurious. The only preventive upon which it is safe to rely is thorough cooking. Those forms which infest wheat and turnips are also harmful to man, in that they destroy his food; while Gordius, which is parasitic in the grasshopper, is indirectly beneficial to man. Important Biologic Facts.—For the first time in the scale of animal life, a celom, or body cavity, appears. It is filled with a clear fluid, and through it extends the straight alimentary tube which consists of pharynx or stomodeum, an intestine, and a rectum. There are no circulatory and no respiratory organs. 1“ Methods of Study in Natural History,” Agassiz, pp. 63, 64. CHA TOGNATHA 45 This branch presents similarities to both Platyhelminthes and Annulata, but the relationship with either is not close. Classification.— Class. Examples. I. Némato’da. — Trichina, Gordius. II. Acan’thocéph’ala.! Echinorhynchus. Ill. Chetog’natha.1 Sagitta. ~1The affinities of the Acanthocephala and Chetognatha with the Nematoda are somewhat doubtful,” Parker and Haswell’s ‘‘ Zodlogy,”’ vol. i, p. 275. BRANCH TROCHELMIN’THES THE animals associated together in this group may have de- veloped independently from trochosphere-like ancestors, but cull ws \) Fig. 37—A _ rotifer, highly magnified (Hy- datina senta): A, cilia; a, anus; b, contractile vesicle; c, water-ves- sels; e, ovary; f, gang- lion. (From MHolder’s ‘“Elements of Zodl- ogy,” American Book Co., Publishers.) since they agree in general character- istics, they have been regarded by some as constituting a well-marked phylum. On account of their size they were formerly regarded as protozoans, but they are multicellular and possess well- defined digestive, excretory, nervous, and reproductive systems. They have no circulatory system. Respiration takes place through the surface of the body. CLASS I. ROTIFERA The Rotif’era (Fig. 37), or ‘wheel animacules,’’ are many-celled, micro- scopic, unsegmented animals, most of which are worldwide inhabitants of fresh- water ponds and streams, or even of mud- puddles and water-troughs. A number of forms are marine. The anterior end is a retractile disk surrounded by cilia, which are locomotive organs as well as aids to securing food. The mobile tail is often composed of tele- scopic rings, rendering it retractile into the trunk. The posterior ring of the tail frequently has a pair of pincer-like stylets. These and the adhesive glands enable the rotifer to attach itself to objects. There is a ccelom. The alimentary tube consists of a ventral mouth, an esophagus, a chewing apparatus (mastax), a glandular stomach, and an intestine which ends in a dorsal anal opening. 46 GASTROTRICHA 47 The nervous system consists of a dorsal ganglion with which are connected one or more eye-spots. There are peculiar tactile organs which consist of ‘ rod-like structures tipped with deli- cate sensory hairs.” There are excretory and reproductive organs. They are dimorphic (of two forms). The sexes are separate. The males are rarer, much smaller, and less highly developed than the female. The female lays thin-shelled summer eggs of two sizes—the larger developing into females, the smaller into males—and thick-shelled winter eggs, which in the spring de- velop into females. The majority are free swimming, being propelled by the trochal disk, but the Bdelloida also have a looping movement like that of the leech. The rotifers may be dried up in the mud for several months, and upon being brought into contact with water they revive, or, some think, their contained eggs bring forth live animals. When in the dry condition they may be carried long distances on the feet of birds or by the wind. CLASS II. DINOPHILEA These, like the rotifers, are modified trochospheres. They are minute and worm-like. They have a prostomium or head, a body of five to eight segments, and a short tail. Both the body and the head are ciliated. The Dinophilea are marine. In the arrangement of the nephridia in pairs, corresponding to the imperfect segments, and in the tendency to seg- mentation, they resemble the Annulata. CLASS II. GASTROTRICHA This class resembles the Rotifera, though the relationship is not close. The class comprises a small number of minute fresh-water forms with spindle-shaped bodies, flattened ventrally. The dorsal surface bears eae rows of cuticular processes, while the ventral surface has two rows of cilia. Classification.— Class. Examples. I. Rotif’era. Brachionus. II. Dindphil’ea. Dinophilus. Ill. Gastrot’richa. Ichthydium. BRANCH MOLLUSCOIDA In this branch there is usually a body cavity, with the ali- mentary tube suspended by mesenteries. The mouth and anal aperture are near together, the dorsal surface being shortened. Inthe adult there is a tentacle-bearing ridge, or lophophore, about the mouth, containing a compartment of the body cavity. The tentacles are used not only in securing food, but in respira- tion. The nervous system consists of one or two ganglia or of a nerve ring.! CLASS I. POLYZOA Molluscoi’da, which usually form colonies of zodids by budding, are Polyzo'a. The character of the colony differs, according to the mode of budding in the different species and the character of the exoskeleton. It varies from a bush-like colony to a calcareous or gelatinous sheet. Each zooid has a crown of ciliated tentacles which can be extended or with- drawn. They are held together by the common exoskeleton formed by the ectoderm. There is no vascular system. The digestive tract is bent like the letter U, the anal opening being near the mouth, within or just outside of the ring of tentacles. The nervous system consists of a gang- lion situated between the mouth and the anal opening. Polyzoans are usually hermaphroditic. CLASS II. PHORONI’DA The classification of this group of worm-like forms of the sea is doubtful. The worm is covered by a leathery cylindric tube into which it may withdraw. The body is unsegmented and bears a crown of tentacles. The mouth and anus are close together and are situated at the tentacle- bearing end of the body. The body cavity is divided into three chambers. There is an alimentary tract and a closed system of blood-vessels contain- ing red blood-corpuscles. The central nervous system consists of a horse- shoe-shaped nerve ring at the base of the tentacles. The Phoronis is hermaphroditic. There is a metamorphosis. CLASS III. BRACHIOP’ODA Brachiopods are marine and were abundant in former geologic times, being very plentiful as early as the Cambrian Period. There are a few living species. They are enclosed in a bivalve shell (Fig. 38), the valves being dorsal and ventral instead of right and left, as in the mollusks. They are at- tached to foreign objects by a peduncle or stalk, which passes through the larger or ventral valve near the hinge. They do not form colonies. 1 Parker and Haswell, p. 313. 48 BRACHIOPODA 49 The shell is only partially filled by the body, and the valves are lined by the mantle lobes, whose free edges are bristled. The mantle lobes enclose a large mantle cavity. In the body is a spacious ccelom, which is extended into the mantle lobes. The ccelom contains the digestive tract, the liver, and the reproductive organs. The latter are chiefly in the mantle lobes. The digestive tract, which is bent much as in the Polyzoa, consists of gullet, stomach, and intestine. The mouth is surrounded by the tentacled lophophore or “arms.” The inner surface of the tentacles is covered with cilia, which set up currents in the water and sweep minute animals and alge: into the mouth for food. The heart, usually present, lies Fig. 38.—Diagram of a brachiopod: b, Tentacles around mouth, m; 1, Beetle: the shell black, the stalk to the’ right. (Kingsley’s “ Compar a- tive Zodlogy,” Henry Holt & Co., Publishers.) dorsal to the stomach, to which it is attached. The nervous system con- sists of an esophageal ring. Sense organs are usually wanting in the adult. Important Biologic Facts.—For the first time, according to the classification used, a closed system of blood-vessels and red blood-corpuscles are found. The digestive tract has been developed into gullet, stomach, and intestine, and a liver also appears. The Brachiopoda were formerly supposed to belong to branch Mollusca. But the valves of the shell are dorsal and ventral, not right and left, while the tentacled lophophore, the character of the nephridia, and the modified trochosphere larva all tend to show relationship with members of branch Molluscoida. Classification.— Class. Example. I. Polyzo’a. Bugula avicularia (Bird’s-head Coralline). II. Phoroni’da. Phoronis. III. Brachidp’oda. Magellania. 4 BRANCH ECHINODER’MATA Plan of Structure.—These animals are characterized by their five-rayed or pentameral plan of structure. While the echino- derm is radially symmetric, the development shows that it is derived from the bilateral type. The larve are bilateral. The REET aa 3 3 sake TT e Sas i Eases SE SSS S EN S SSS Tig. 39.—Solas/ter endeca (small specimen, natural size), oral view. (Bulletin, U.S. F. C., 1902.) central portion is the disk, from which arms or rays project, as seen in the starfish. Close examination will reveal this penta- merous plan in the sea-urchin and in the sea-cucumber. For, suppose the rays of the starfish were flexed and their edges joined, the form of the sea-urchin would appear. Again, 50 GEOGRAPHIC DISTRIBUTION BL lengthen the sea-urchin in the direction of the mouth to aboral surface, and you have the form of the sea-cucumber. The crinoid also reveals this plan, not so clearly defined, but it is to be seen by the careful observer. The number of rays varies in the starfish, the author having found them with four, six, or even as many as twenty-two rays. letin, U.S. F. C., 1902.) The Skeleton or ‘‘ Tesi.”—The body wall is composed of a thick leathery substance. In the mesoderm, under the epi- thelium, calcareous plates arise, many of which are armed with spines for protection. They are greatly protected also by their resemblance to their environment. Geographic Distribution.— All echinoderms are marine, being abundant even in the deep sea. They are found in all parts of the globe, but are most abundant in the tropics. At the breed- ing season most of the free species frequent the shallow waters ‘ By BRANCH ECHINODERMATA near the coast, where the ova are fertilized in the water. Hchino- derms of the same species are often gregarious. The water-vascular system is a marked characteristic of echinoderms (Fig. 41). It begins externally with the cal- snuscles of the pyloric caeca aasosgageseee “cardiac stomach ~.--intestinal caecum, pyloric caecush ‘muscles of the pyloric caeca Fig. 41.—Dissection of a starfish (Asterias sp.). (From Kellogg.) careous perforated madreporic plate which is connected by a calcareous (Stone) canal with the central ring around the mouth, from which tubes proceed along each arm, in the star- METAMORPHOSIS 53 fish. On the inside of the floor of each ray are the ampulle, small bulb-like water-sacs, which are connected with the tube- feet on the outside of the ray. ‘“‘ By a contraction of the deli- cate muscles in the walls of the ampulle the fluid in the cavity is compressed, thereby forcing the tube-feet out. By the con- traction of muscles in the tube-feet they are again shortened, while the small disk-like terminal sucker clings to some firm object. In this way the animal pulls itself along by successive steps.” By the aid of these ambulacral or tube-feet the starfish is able to turn over if placed upon its back. They also act as suckers to fasten the starfish to the rocks. When once this is accomplished, arm after arm may be broken off before the animal can be pulled loose or the feet will relax their hold. So-called blood canals accompany the ring and radial canals, and associated with them are sometimes two intestinal blood- vessels.! Nervous System.—“ There is a nerve ring and radial nerve, frequently in the ectoderm, to which may be added an entero- ceelic or apical nervous system, possibly of peritoneal origin.” The circulating fluid is somewhat lymph-like and the circula- tion slow. ‘Respiratory organs are represented by the branchie, or thin- walled outpushings of the ccelom, either around the mouth, as in the Echinoi’dea, or on the aboral surface, as in the Asteroi’dea, the burse of the Ophiuroi’dea, the branchial trees of the Holothu- roi’dea, and the various parts of the ambulacral system.””? The alimentary tube is complete, that is, shut off from the body cavity and runs through the body. Its length depends upon the food of the echinoderm. In carnivorous forms, as the star- fish, it is short, but in vegetable feeders, as the sea-urchins and sea-cucumbers, the alimentary tube is two or three times the length of the body. Multiplication is sexual, as a rule, the sexes being separate except in rare cases. Fertilization takes place in the water. They never form colonies by budding. The metamorphosis, or change from the larval to the adult form, is as marked as that from the caterpillar to the butterfly. x Herwig “Manual of Zodélogy,”’ Kingsley, p. 331. 2 Tbid. 54 BRANCH ECHINODERMATA The larva is bilateral,! while the adult is radial, the eee noyouuet being complex. Generally the young shift for themselves, but cases are recorded of broods being cared for by the female echinoderm in a pouch on the dorsal surface. - CLASS I. ASTEROIDEA To this class belong the starfishes, with their central disks and varying number of rays, five being the typical number. They live along rocky seacoasts. Fresh water kills them. The common starfish (Aste’rias vulga’ris) is abundant along the Atlantic coast, especially in the vicinity of oyster-beds, to which they do much injury by devouring the oysters. Star- fishes are found also on the Pacific coast from Sitka to southern California. They are said to devour small fishes as. well as erabs. The body wall is composed of a thick leathery substance in which is embedded a great number of calcareous ossicles (12,000 by estimation), many of which are armed with spines for protection. Between the spines on the aboral surface are soft stalked projections ending in pinchers, called pedicella’rie, with which it cleanses the surface of the body and protects itself from parasites. The alimentary tube extends from the oral to the aboral surface. It consists of a mouth, a short esophagus, and a large sac-like stomach, which is five lobed and fills most of the disk. (See Fig. 41, p. 52.) The stomach is eversible and is furnished with muscles for withdrawing it. From the pyloric, or upper, division of the stomach the ceca extend, a pair into each arm. These ceca secrete much fluid, which is emptied into the pyloric portion of the stomach and used in digesting the food. From the stomach a short conical intestine extends upward to the aboral surface. The aboral opening from the intestine is not exactly in the center of the disk and is often difficult to find. In a few forms it 1s wholly obliterated. Locomotion.—The arms are somewhat flexible, and, aided by their tube-feet,? enable the starfishes to move slowly along in 1 Hertwig’s ‘Manual of Zoélogy,” Kingsley, p. 331. 2 See text, Water-vascular System of Echinoderms, p. 52. ASTEROIDEA 55 search of food. The starfish, by clinging with its sucking disks, ean travel along horizontal or vertical walls It can bend its arms or even its central disk, when necessary, to pass through openings or crevices between rocks. As it moves so slowly, its direct dispersal is very limited, but since it is not attached, it is indirectly distributed by the tides and currents. The exceed- ingly minute young are often borne great distances in this way. Foods and Feeding.—The starfish is carnivorous and very voracious; indeed, it seems to eat continuously. It feeds upon barnacles, clams, oysters (Fig. 42), and, it is said, even small fishes, or, failing of these, it will eat the garbage thrown along the shore, thus acting as a sort of scavenger. The worst damage it = iB all Fig. 42.—_Starfish attacking oysters. (From Fifth Report of Connecticut Bureau of Labor Statistics.) does by its gluttony is to the oyster-beds. Oysters and clams close their shells to the starfish, but it keeps up a steady pull un- til it gets them open, when it reaches its arms about its prey and extrudes the lower part of its stomach, envelops the soft parts, pours out the digestive fluids about them and absorbs them, then withdraws its stomach, leaving the indigestible parts of its victim outside the body. Further digestion of the absorbed food takes place in the pyloric portion of the stomach, aided by the secretions of the hepatic ceca. The fact that all indigestible parts are “ rejected ”’ may account for the shortness of the in- testine, and certainly does account for the small or lacking anal aperture, since there is little left to be ‘“ ejected.” 56 BRANCH ECHINODERMATA The nervous system consists of a circumoral nerve ring, from which a nerve proceeds along the ambulacral groove of each arm to its tip, where it ends in a so-called “ eye-spot ” which has been proved sensitive to light. Special Senses.—Besides the general sense of touch and the ““ eye-spots,” already mentioned, there is at the distal end of each ray a tentacle-like organ which is supposed to be the organ of smell. Multiplication is sexual. Fertilization takes place in the water. The starfish may reproduce asexually, for if a ray be broken off,! either accidentally or purposely by the animal itself, it has the power of reproducing a new disk as well as the rest of the arms, with their internal organs. Similarly, if all the arms are torn off, the disk has the power of growing out new ones. The young are bilaterally symmetric, free-swimming animals. The metamorphosis is complicated, resulting finally in the radial plan of structure of the adult. The starfish, Linckia linckia, is a host for a parasitic gastero- pod (Thyca). Some starfishes are gregarious. In size they vary from less than 1 inch to 3 feet in diameter. In color they may be yellow, brown, red, or purple. Geologic Distribution.—The starfishes appeared before the close of the Cambrian Period, and have been represented in every age up to the present. CLASS II. OPHIUROIDEA These echinoderms resemble the starfish. The arms are slender, jointed, muscular, and are used for locomotion (Fig. 43). The arms may be much branched, as in the basket-fish, and are not hollow as they are in the starfish. The ambulacral groove is closed, the tube-feet are on the sides of the arms, and have no suckers at their distal ends. The arms are much more slender and more flexible than those of the starfish, and locomotion, which is faster than that of the starfish, is accomplished by the lateral movements of the arms, Some species have the power of throwing off pieces of their arms when disturbed. The digestive organs are confined to the disk, the hepatic 1 Parker and Haswell, p. 400. OPHIUROIDEA i ezeca are absent, and the anal opening is lacking. The madre- poric plate is on the oral side. Food.—They are carnivorous, feeding upon worms, crabs, and shell-fish. They are also scavengers. Multiplication Some lay their eggs in the water, where they are fertilized and develop into a pluteus stage like that of the Fig. 43.—Gorgonoceph’alus agassiz’ii (one-fourth natural size). Oral view. (Clark, in Bulletin 550, U.S. F. C., 1902.) Echinoidea, while others are viviparous and care for their broods. In many species there is also a kind of asexual repro- duction, the animal dividing through the disk and each half regenerating its ‘‘ other half.” There are several hundred species known. These echino- derms are variously called brittle-stars, serpent-stars, and sand- 58 BRANCH ECHINODERMATA stars. The one most common on our shores (Ophiopholis) is of a ‘‘ general red hue spotted with brown and paler red.” CLASS III. ECHINOIDEA The globular or disk-like sea-urchins have the pentameral plan, as a cleaned “ test” or shell (Fig. 44) will show. The body wall is composed of several hundred pentagonal calcareous plates arranged in regular order in twenty rows, the whole forming a sort of thin case or shell (see Fig. 44). A YY y == PO) Gee L Fig. 44.—Sea-urchin (EHchi/nus micros/toma) with spines nearly all removed from “ test.’’? (Chapin and Rettger.) The ossicles, or plates, are armed with very long sharp spines for defense (Fig. 45). Alternate rows of plates are perforated for the passage of the tube-feet, there being no grooves. These ten rows of perforated plates constitute the ambulacral areas, and the ten rows of unperforated plates constitute the inter- ambulacral areas. Color.—The colors are brown, olive, purple, red, green, or blue. The protective resemblance is good. The ambulacral system of the sea-urchin is similar m plan ECHINOIDEA 59 to that of the starfish. Locomotion is very slow and is per- formed by the tube-feet, aided by the long spines. The pedicellariz are similar to those of the starfish, but are more fully developed, having three pinchers instead of two. The food consists largely of green alge and brown seaweed, for the sea-urchin is a vegetable feeder, though it eats small marine animals also. Digestive System.—There are five hard white teeth with which they gnaw their food. These teeth are connected with a —— eS = Soy Fig. 45.—Strongylocentrotus drobachiensis. Oral view, showing spines, “feet,” and teeth. (Clark, in Bulletin 550, U.S. F. C., 1902.) complicated calcareous framework under muscular control. The whole apparatus is called “ Aristotle’s lantern.”’ The intestines are long, coiling about two and a half to three times, instead of being short like those of the carnivorous star- fish. The hepatic ceca and gastric pouches are absent. This lack, as well as the structure of the mouth parts and the long coiled intestine, correlates with the feeding habits of these herbivorous animals. 60 BRANCH ECHINODERMATA The nervous system is upon the same plan as that of the starfish. Multiplication.—The eggs are laid in the water and fertilized by the tadpole-like sperm cells. Some forms have a marsu- pium, or brood-pouch, in which the eggs are hatched. Development.— After fertilization, segmentation of the egg takes place until the bilaterally symmetric young “ pluteus,”’ which is very unlike the adult, appears. It is free swimming and lives on minute organisms it can procure in the water. As it develops it takes on the radiate or pentameral plan of its branch. The ‘‘ sand dollars’ so common on both the Pacific and the Atlantic coasts are flat sea-urchins with short spines. Geologic Distribution—A primitive type of sea-urchin ap- peared in the Ordovician period.! CLASS IV. HOLOTHUROIDEA Holothurians are free, and a close examination reveals the pentameral plan of the branch, although they are more or less bilaterally symmetric. Fig. 46.—Cucuma’ria frondo’sa, side view. Note tentacies and rows of feet. (Clark, in Bulletin 550, U.S. F. C., 1902.) The shape (Fig. 46) is much like that of the garden cucumber in our common varieties, but some are long and slender and 1 Seott’s ‘‘Geology,” p. 381. HOLOTHUROIDEA 61 more worm-like in appearance. Some are so long and slender that they are sometimes thought to be worms. The size varies from 3 inch in one species found upon the Massachusetts coast, to 3 feet, in another species found in Monterey Bay, California. The body wall is tough, leathery, muscular, and not so rigid as in the starfish or sea-urchin, although minute calcareous spicules are scattered throughout it. The tube-feet may be in rows, or scattered, or entirely want- ing, depending upon the species, of which several hundred are recorded. The sea-cucumbers move with their long axis parallel to the ground. They creep along . with the help of the tentacles. Protective Resemblance. Their colors, which are reddish brown or yellowish, harmonize so closely with those of their en- vironment that their protective resemblance is almost perfect. As the animals rest on the bot- tom of the sea with their feathery tentacles spread out they closely resemble the vegetation of the sea bottom. A person may stand within a foot of the sea- cucumber and not see it. The alimentary tube (Fig. 47) abe is soveral times the length of til. 47,, Soxeueumur (Mote the animal, and the intestine is mentary tube, al.t. (Leuckart.) coiled in a uniform manner. The food of the holothurians consists of organic matter obtained from the sand which they swallow, or of small animals which they capture with their tentacles. They are nocturnal in their feeding habits, resting quietly during the day on the bottom of the sea or buried in the sand. The respiratory system consists, probably, of the so-called “‘ respiratory trees,” two hollow, much-branched organs open- ing into the cloaca, which is periodically filled with water. 62 BRANCH ECHINODERMATA They are probably excretory organs also, and are connected with the manipulations of the tentacles.' Multiplication is generally similar to that of the starfish, except in rare cases of hermaphroditism. There are also cases recorded of the female caring for her brood in dorsal pouches. In unfavorable conditions they void the whole viscera and yet live and replace the lost parts.’ In the development from the bilateral larva to the radial adult there is a marked metamorphosis. Several species are hosts for certain parasites. A small fish infests the cloaca and branchial trees of one or two species. A snail lives in one species and a mussel in another. Use.—They are used for food by the Malays, who call them ‘“‘trepang,” and use them principally for soups. Millions of them are captured in the south seas, where hundreds of vessels are engaged in the trepang fisheries. Distribution.—Holothurians are widely distributed, being found from the arctic to the tropical regions. Geologically, they date from the Carboniferous Period. CLASS V. CRINOI’/DEA Crinoids are fixed echinoderms with a flexible stem or stalk of calcareous perforated disks, bearing a flower-like body at the top of the stem (Fig. 48). This body consists of a cup- shaped center bearing’ five or ten arms, usually branched. The ‘ feather stars,” found at a less depth, later become de- tached and float around in the water. Ambulacral Grooves.—Five ciliated ambulacral grooves (Fig. 49) extend from the mouth out on the arms and their branches, and give off branches to the pinnules. They serve as channels through which the food passes to the mouth, and also for the purpose of respiration. Food.—They feed on small crab-like animals and on marine unicellular animals and plants. The nervous system consists of a nerve ring surrounding the mouth, and given off from this nerve ring are a series of ambu- lacral nerves which extend the entire length of the arms and pinnules. 1 Parker and Haswell’s ‘“ Zodlogy,” vol. 1, p. 372. 2 Tbid., p. 400. ® CRINOIDEA 63 Fig. 48.—Crinoid (Brehm.) Fig. 49.—Mouth area of a crinoid (Comat’ula), showing the course of the intestine leading from the mouth (m) to the vent (a); g, grooves Jeading from arms to mouth. (From Kingsley’s “Comparative Zodlogy,’’ Henry Holt and Co., Publishers.) Digestive System.—The mouth is directed upward and leads into the digestive tract, censisting of esophagus, stomach, and 64 BRANCH ECHINODERMATA intestines. The interradial anal opening (see Fig. 49) is situated near the mouth. Multiplication—Crinoids multiply by eggs, which pass through complex changes before reaching the adult stage. Habitat—The living crinoids are deep sea animals with the exception of two genera, which live at a less depth. Some have been dredged from a depth of 11,100 feet. At this depth the water pressure must be enormous. Geologic Distribution—Primitive types (the cystids and blastoids) of this group are among the most ancient fossils. True crinoids appeared before the close of the Cambrian Period. They reached their culmination in the Carboniferous Period. The crinoid fossils of this period are so numerous that many beds of limestone are composed principally of them. Burlington, Iowa, and Crawfordsville, Indiana, are noted for their numerous and well-preserved fossil crinoids. Crinoids, though formerly of such vast numbers, are now almost extinct. Important Biologic Facts—Echinoderms are radially sym- metric, but embryology shows that they have developed from the bilateral type. It is reasonable to regard those classes of echinoderms as the more ancient which have the radial sym- metry less completely developed.! The locomotor-ambulacral system is found in no other branch. The echinoderms are a singularly isolated group, and we look in vain among the known members, living and fossils, of other branches for any really close allies. Classification.— Class. Examples. I. Asteroi’dea. Starfishes. II. Ophiuroi’dea. “¢ Brittle-stars.” III. Echinoi’dea. Sea-urchins. IV. Holothuroi’dea. Sea-cucumbers. V. Crinoi’dea. Sea Lilies, ‘‘ Feather-stars.” VI. Cystoi’dea. Fossil. VII. Blastoi’dea. Paleozoic fossil, asin Class VI. 1 Parker and Haswell’s “ ZoGdlogy,” vol. i, p. 401. BRANCH ANNULATA THE branch Annila’ta is distinguished from the other branches of worms by having external and internal segmentation, that is, being divided into rings or segments (metameres) ‘“ containing homologous organs or similar portions of a continuous organ.””! They have, usually, a well-developed ecelom or body cavity, divided into segments by muscular partitions or septa. These worms are bilaterally symmetric. The body is usually elongated. CLASS I. CHETOPODA Class Cheetdp’dda consists of fresh-water and marine annelids which bear sete, or bristles. The sete arise from special fol- licles, and may occur singly or in bunches. These setz, which are controlled by special muscles, act as tiny levers in locomo- tion. They have a body cavity which is partially divided into com- partments corresponding to the segments. The alimentary tube extends through the body and is usually constricted at the septa. There is usually a well-developed circulatory system. Respiration is usually through gills or branchie and through the body wall. In some forms the sexes are distinct, while other forms are hermaphroditic. Fresh-water annelids de- velop without a metamorphosis, but in many marine forms the trochosphere larvee occur. Few are true parasites, but a number are commensal, habitu- ally associating with other animals for their food and shelter. Many sea-worms are phosphorescent: The earthworm (Lum/bricus) has an elongated cylindric body of many segments or metameres. Digestive System (Fig. 50).—The mouth is covered by a rounded, lobe-like projection, the prostomium. The mouth leads into a small buccal cavity, back of which is the larger, thick-walled, muscular pharynx. This pharynx can be pro- * Galloway’s “ Zodlogy.” 5 65 66 BRANCH ANNULATA truded and retracted. Fig. 50.—Eartiworm dissected to show aliment- ary tube, al. ¢t (From Jordan and Kellogg, “Animal Life,’’? D. Apple- ton and Co., Publishers.) The radially arranged muscular fibers which run from the pharynx to the body wall retract the pharynx and at the same time dilate it. Back of the pharynx is the narrow esophagus, with a pair of pouches and two pairs of ealciferous glands, which communicate with these pouches and which contain alimy fluid. Posterior to the pharynx is the thin-walled crop, and back of this is the very thick-walled rounded gizzard, with its tough, chitinous lin- ing, in which the food is ground by sand, and from which the intestine ex- tends to the anal opening in the pos- terior segment. The typhlosole, a prominent ridge extending along the middle of the dor- sal surface of the intestine and dipping down into the interior, renders the hollow of the intestine crescent shaped. This typhlosole increases the absorb- ing surface and is well supplied with blood-vessels. The circulation is carrried on in a well-developed system of blood-vessels. The dorsal tube extends along the median line of the dorsal surface’ and is plainly seen in the live earthworm. The forward movement of the blood can usually beseen. The ventral blood-ves- sel lies below the alimentary tube. In this ventral blood-vessel the blood is pro- pelled backward by the peristaltic action of the tube. The three smaller blood- tubes, the subnural and two lateral nural tubes, lie close to the nerve cord. Each segment has a transverse vessel connecting the dorsal and ventral blood-vessels. Those from the sixth to the eleventh CH®TOPODA 67 segment are dilated and pulsate ryhthmically, hence are some- times called hearts. The blood is red, the color being due to the presence of hemoglobin (the same substance which makes our blood red) in the liquid itself, though the blood contains . colorless corpuscles. The nervous system consists of a double cerebral ganglion connected with a double ventral chain of ganglia by a pair of commissures which pass around the esophagus. The earthworm has no eyes, yet it can distinguish not only light, but the direction from which it comes, and it will crawl ““ away from the light of high intensity and toward a light of low intensity.”” This tendency, and the fact that the moisture of the skin would be rapidly evaporated in daytime, and the ab-- sence of enemies, induce the earthworms to feed at night. The earthworm has no organs of hearing, but its general sense of touch is so delicate that it detects the approach of danger by the jarring of the earth about its burrow. It can distinguish and choose between different kinds of food, so it must have a sense akin to smell or taste. It is thought that the ‘“‘ goblet-shaped bodies”? on the prostomium and on the anterior segments are the seat of this sense. The body wall is composed of, first (on the outside), the cuticle, then the epidermis, the dermis, a muscular layer of circular fibers, a layer of longitudinal muscle-fibers, and underneath this the ccelomic epithelium which lines the body cavity. Respiration takes place through the thin moist skin which is everywhere underlaid by a network of blood-vessels. These absorb the oxygen from the air and give off the carbonic acid gas through the skin. Locomotion.— Each segment, except the one at each end of the worm, is furnished with four pairs of sete, or short, stiff, chitin- ous bristles. They arise from the setigerous glands or sacs made by the infolding of the cuticle. By special muscles, at- tached to the base of each of these sacs, the setze can be turned in different directions. In locomotion the earthworm uses these setee as levers. When it moves forward the setz are turned backward and stuck into the soil, the longitudinal muscles contract, pulling the body together, then the circular muscles contract, making the body smaller and longer and fore- 68 BRANCH ANNULATA ing it forward, since the sete prevent its moving backward. When the earthworm moves backward the sete are directed forward, and the same processes propel the worm backward. Excretion.—In all the segments of the body except the first three and the posterior one is a pair of tubular kidneys (nephri- dia). Each begins in a ciliated funnel—which opens into and takes up the waste from the body cavity—in the back part of a segment, and continues in a long, much-looped tube, which opens externally by a small excretory pore on the ventral surface of the segment posterior to the one in which the funnel- shaped beginning is situated. Multiplication—The earthworm is hermaphroditic, but cross-fertilization takes place. The lateral and dorsal portions of the segments from the thirty-second to the thirty-seventh are swollen and somewhat fused together, forming a sort of girdle (the clitellum). The glands of this clitellum secrete a viscid fluid. This secretion hardens, upon exposure to the air, and forms a band or collar about the clitellum. This collar moves forward, gathers the eggs and sperms! as it passes the openings, and finally is slipped off over the head.?, The ends of the collar now close and it forms a tough egg-capsule. The egg-capsules are hidden under stones, boards, or logs, or are buried in the earth, especially about barnyards and compost heaps. ‘‘ The worms are about 1 inch long when hatched.’ They hibernate below the frost line in winter. Enemies.—The chief enemies are moles and birds. To avoid the birds they feed at night or early morning, and some- times drag a pebble into the mouth of the burrow, closing it after them. The marine worms (Polyche’ta) are dicecious, and the young undergo a more or less complete metamorphosis. The larva is a trochosphere.4 Some burrow in the sand; some are free swimming; some secrete a mucus which hardens and forms tubes; others form tubes by sticking together with mucus pieces of shell, sand, mud, or limestone. Most of the tube-building species are fixed to some object, but a few carry their tubes about. Many of these marine worms live in shallow water, but some have been found at a depth of 3000 fathoms. 1 These have been obtained from another earthworm. 2 Shipley and MacBride, p. 100. 3 Colton, ‘‘ Descriptive Zodlogy.” 4 See Glossary HIRUDINEA 69 The nereis, or sand-worm, which is found on the seashore, has a distinct head, bearing eyes and tactile sense organs, such as tentacles and palpi. Each segment has a fleshy outgrowth, the parapodium, bearing many bristles. “This is the first appearance of true appendages, though they are not jointed to the body nor in themselves.” The sand-worm varies in color in different stages, and the length varies from 6 inches to 2 feet. It has an eversible pharynx, which, when infolded, conceals two horny jaws. These jaws are deeply notched and the ends are incurved. When food is taken the pharynx is everted, the Jaws thrust forth, and the prey seized and swallowed. CLASS II. GEPHYR’EA Class Géphyr’ea is composed of oval or spindle-shaped worms, which are unsegmented in the adult form. Sete are entirely wanting. The mouth, which is at the anterior end, is either surrounded by tentacles or overhung by a ‘‘ proboscis ”’ which may be several times the length of the body. These worms are widely distributed. They live in both deep and shallow water and, ‘for the most part, either in natural rock-fissures or in burrows which they excavate in sand or mud or in coral or rock.” CLASS III. HIRUDIN’EA The body of the leech tapers at both ends and is flattened dorsoventrally. It is composed of many segments which are superficially divided into several rings, so that there are not so many true segments as there are surface rings. The principal order of this class contains the common fresh- water leech familiar to barefoot boys. It is a temporary para- site on vertebrates. The leech (Fig. 51) has no setz nor appendages, but is pro- vided with two suckers. The one on the posterior ventral sur- face is used for attachment in locomotion, and the other, which surrounds the mouth and is not well developed, is used in suck- ing the blood into the large crop. In the pouches of this crop, it is said, enough blood can be stored to last a year. A narrow stomach and a short intestine follow the pouched crop. The ccelom is considerably obliterated by a growth of muscle and connective tissue, called parenchyma. Leeches are hermaphroditic. The eggs are usually laid in small packets or cocoons, and these are deposited in moist 70 BRANCH ANNULATA soil. The eggs are hatched in four or five weeks, but it takes them several years to mature. Some leeches are said to live twenty years. Leeches are widely distributed. Many of them are in- habitants of fresh water. Some live in salt water, while others live in the forests of many regions, especially those of the tropics, where they are the terror of men and beasts. One species ( Hiru’do sanguisu’ga) is a parasite in the nasal passages of man. Another (H@emop/- sts vo/rax) lives in the pharynx or trachea of the horse, being taken in with water when small. Another form (Branchel’lion) is a permanent ex- ternal parasite on fishes. Distribution.—The members of branch Annulata are widely distributed, the rep- resentatives of its many species being found from frigid to tropical regions, and even in the isolated islands of the sea. It is known that marine worms existed in the Cambrian Period by their “ tracks and borings in the sand, which are now consolidated into hard rocks.” Economic Importance.—The earth- worm swallows the soil which it exca- vates for the sake of the partially de- cayed organic matter it contains, which the worm appropriates to the building up of its body tissue. The indigestible portions it deposits on the surface at nieces } night as coiled castings. They also feed = Bee ee es on fresh or decayed leaves which they sucker; , posterior drag into their burrows, and sometimes sucker; c, anus; d,d,d, pon young seedlings and tender roots. stomach; @, esophagus; : : i, intestine: s, s, glands Darwin, who studied the earthworm for of the skin. (Holder.) forty years, estimated that in the tillable soil of England there were fifty thousand earthworms to the acre, and that they brought to the surface from 10 to 18 tons of soil annually. In this way the whole HIRUDINEA fal superficial layer would be enriched by passing through their bodies in a few years. Their burrows may extend vertically or obliquely for several feet underground, their depth depending upon the distance of the moist soil from the surface. They are connected by underground tunnels, so that the soil is thoroughly exposed to the chemical action of the gases and acids of the air and water.”! Thus the action of the earthworm has both a chemical and a mechanical effect upon the soil. Leeches were formerly used very frequently by doctors when bleeding was more often practised. They are still sometimes thus used. They are raised in France for commercial purposes. Swamps are stocked with them and they are fed upon old and worn out farm animals. Important Biologic Facts.—This branch is distinguished from all preceding groups by its metameric segmentation. The excretory system is characterized by the peculiar nephridia. There is a well-developed circulatory system and a circulating fluid containing hemoglobin. In leeches eyes are found, while the “ goblet-shaped organs’ in leeches and earthworms are thought to be the seat of smell or taste. True appendages ap- pear in the Nereis. The trochosphere larvae show relationship between Chetopoda and the Turbellaria and the Nemertinia. Classification. Class. Examples. I. Cheetdp’oda. EKarthworms, Sand-worms. Il. Géphyr’ea. Sipunculus. III. Hirudin’ea. Leeches. ‘Jackson and Daugherty, “Agriculture Through the Laboratory and School Garden.” BRANCH MOLLUS’CA THESE animals have soft, unsegmented bodies, as contrasted with the segmented Arthropoda. The body is generally bi- laterally symmetric, but it may be asymmetric, as in the snail. They vary in size from a fraction of an inch to from 2 to 5 feet in length; and in weight from a fraction of an ounce to 500 pounds. The body may be naked, as the slug; or coyered f Fig. 52.—Part of a bunch of oysters from Great Point Clear Reef, showing attachment of barnacles and mussels. (Bulletin, U.S. F. C., 1895.) with a univalve shell, as the snail; or with a bivalve shell, as in the common mussel; or it may have an internal horny pen, as in the squid. The structure and form of the Mollusca are very various, and the number of known living and fossil species exceeds forty thousand. Some mollusks are marine, some are fresh-water forms, and others are terrestrial. 72 PELECYPODA 73 The circulatory system consists of a dorsal heart of one ventricle and one or more auricles, enclosed in a pericardium. Aortze carry the blood from the ventricle to different parts of the body, but the blood-vascular system is not entirely closed. Respiration is carried on through the body wall in a few Mollusca, but most of them breathe through gills or lungs. The nervous system is characterized by three pairs of ganglia which are joined by connective nerve cords. The cerebral ganglia are situated dorsal to the esophagus and supply the tentacles and eyes. The pedal ganglia lie ventral to the mouth and supply the foot and otocysts. The visceral ganglia, also ventral, but farther back, supply the body, the mantle, and the so-called “ osphradia,”’ or olfactory organs. Some mollusks lack special sense organs. _ Locomotion is accomplished by the single so-called “ foot,” a muscular plowshare-shaped thickening of the body. Multiplication The Mollusca may be sexually separate or hermaphroditic. This branch includes some very valuable food animals for man, as clams and oysters. Other examples are snails, slugs, scallops, cuttle-fishes, squids, and fresh-water mussels. CLASS I. PELECYPODA This class is called by various names by different zodlogists, depending upon the character taken for the basis of classifica- tion—as Aglossa (without a tongue), Acephala (without a nead), Bivalva (of two valves), Péléc¥Yp’oda (hatchet-footed), Lamellibranchiata (leaf-like gilled). We may then characterize this class as the hatchet-footed, headless, tongueless, bivalved, leaf-like gilled mollusks. Mussels, clams, and oysters are com- mon examples of this class. The body is soft, unsegmented, and is modified into the large “foot ” used for locomotion. The mantle, a great fold of skin, covers the body, one lobe over each side. Between the mantle lobes and the body are the four large leaf-like gills. The labial palpi are the small leaf-like structures anterior to the gills, and lead into the mouth. This organ secretes the shell. Food consists of small organisms which the water carries into the mantle cavity and to the ciliated labial palpi, which 14. : BRANCH MOLLUSCA pass the food into the mouth. From thence the food passes into the stomach and to the long coiled intestine which passes through the pericardium, usually perforates the ventricle, and ends dorsal to the posterior adductor muscle. The Pelecypoda are sexual and sometimes hermaphroditie. There is a metamorphosis, there being usually a trochosphere stage. The sea mussel (Mytilus) is an example of this class. Great clusters of this edible mussel are found just below low-tide marks. The shell is generally of a purple or dark color. The long slender foot (Fig. 58) throws out yellowish horny fibers (the byssus), by which the mussel attaches Fig. 53—Mytilus edulis: O, Mouth; S, labial palps; P, foot; B, byssus secretion; Br, gills; M, thickened edge of mantle. (After Claus.) itself to foreign objects. If food becomes scarce or conditions unfavorable, it can detach itself and slowly move to another position by stretching out the threads of the byssus and attaching them ahead or above, and then ees itself up to them, hence it is sometimes called the “ climbing mussel. Ano/mia, of the same order as My/tilus, is permanently fixed. The oyster (Os’trea) is amember of this class, which in adult life is fixed to the sea bottom or to some foreign object—very often the shell of another oyster. Great clumps (see Fig. 52, p. 72) may be thus fastened together, but their union is not organic. Oysters vary in size from a few inches to 2 or 3 feet, the largest being a Japanese species. The shell of the oyster (Fig. 54) is rougher than that of the clam, and the hinge is at the pomted end, which corresponds to the anterior end of the clam. Its two valves are not alike, but the lower or left one is much larger and becomes deep enough to contain the body, while the upper or right valve is flat and serves as a lid. There is but one adductor muscle. PELECYPODA aD By its contraction the shell is closed. Its location is changed from year to year as the animal grows. A brown scar in the shell indicates where the attachment has been. The oyster can open its shell but little. The oyster, since it is fixed, needs no organ of locomotion, and so has no foot. Neither has it any siphon, but the food-bearing water (Fig. 55) enters along the curved border of the shell and passes out near the larger Fig. 54.—Shell of typical American oyster: 1, Inner face; 2, outer face. (Report U. 8. Geol. Survey.) end on the straight side. A fresh supply of sea-water is necessary to fur- nish it with food and oxygen. If the oysters settle too deep in the mud or if they are covered by silt and sand in time of storms they smother. Our species of oysters (Ostrea virginiana) is bisexual, while the European species are hermaphroditic.1. The reproductive organ is attached to the 1“ Hertwig’s Manual of Zodélogy,’”’ Kinglsey, p. 367. 76 BRANCH MOLLUSCA large adductor muscle. The eggs are deposited in the water. They are very numerous. It has been estimated that one female will produce from 9,000,000 to 40,000,000 eggs in a single season. The breeding season is from May to August. If the eggs are not eaten by enemies or carried away by currents, they sink to the bottom. After a few hours of develop- ment the larvee swim to the surface. Multitudes of these larve are de- voured by surface-living fishes. The larvee (Fig. 56) swim by means of cilia. Ina few days the larve or fry, as they are called, sink to the bottom Fig. 55.—Food of South Carolina oyster. A few typical organisms (x 225). Numbers 1 to 20 are diatoms. 1-5, Navicula (Bory); 6, N. didyma (K.); 7, Pinnularia radiosa (?) (K. 8.); 8, Amphora sp. (K.); 9, Pleurosigma fasciola (E.8.); 10, P. littorale (S.); 11, P. strigosum (8.); 12, Actinocyelus undulatus (K.); 13, Coscimodiscus radiatus (E.); 14, Cyclotella rotula (E.); 15, Synedra sp. (E.); 16, Diatoma sp. (De C.); 17, Cymbella sp. (Ag.); 18, Mastogloia smithii (Thw.); 19, Triceratium alternans (Br. Bai.); 20, Biddulphia sp. (Gr.); 21, Grain of pine pollen (Pinus rigida); 22, Foraminifera (Rotalia); 23, Zodspore (Ulva?); 24, Spicules. (After Bashford Dean.) (From Moore, U. S. Com. of Fish and Fisheries. ) and attach themselves by the mantle-fold to some other oyster or to any object with which they come in contact. It takes them from three to five years to attain their growth. The blue crab (see Fig. 74, p. 101) is very destructive to the young oyster. One of the greatest enemies of the oyster is the starfish (see p. 55). Other enemies (Fig. 57) are boring snails, boring sponges, and internal parasites. One little crab (Pinnothe’res) which lives in the mantle cavity seems to be an example of symbiosis rather than a parasite; at least it does not appear to harm the oyster. PELECYPODA 77 Oysters abound in quiet, shallow inlets of the Atlantic coast south of Cape Cod, and of the Gulf of Mexico. We have the best oysters in the world.! Our most extensive oyster-beds are on the Chesapeake Bay, at Baltimore, where they cover 3000 acres and furnish millions of bushels yearly. We not only supply the markets of our own great cities, but send large quantities to British markets. Oysters are found also on the Pacific coast, on the coasts of Europe, of Australia, and of Japan. The scallop (Pecten) has an almost round, fluted shell with a straight hinge without teeth, and with unequal valves, one being more nearly flat than the other. The shell is usually brilliantly tinted. The foot is rudi- mentary or altogether lacking. The mantle- folds are fringed with slender tentacles and the edge of each lobe is set with a row of brilliant bluish ‘ eyes.”’ When at rest the scallop lies on the sea bottom with its one ad- ductor muscle relaxed and its shell open. If disturbed, it quickly closes the shell by con- tracting the strong muscle. This catches a quantity of water which is forcibly ejected through a round aperture at either end of the peel ene of the hinge. The reaction caused by forcing this water against the great agus : : body of water outside propels the animal for- _ Fig. 56.—Right side of ward. Thus, by rapidly opening and closing embryonic oyster, six days its shell, it swims through the water with old: m, Mouth; s, vent; /, comparative ease. right lobe of liver; ol, The edible scallop (Pec’ten irra’dians) is velum. (Moore, Bull. U. about 24 inches in diameter and its color S. F. C., 1897.) varies from a whitish to a reddish or purple hue. The adductor muscle is the portion used by man for food. This scallop is found on the Atlantic coast south of Cape Cod. Pec’ten max’imus, found on the coast of Great Britain, in water 30 to 40 fathoms deep, is much larger. Its deeper shell was formerly used as a baking-dish for oysters, hence the origin of the term “ scalloped oysters.”’ The shell of another form common in the Mediterrnaean Sea (Pec’ten elas us) Was worn as a badge by the crusaders returning from the Holy Land. The so-called pearl-oyster (Meleagri’na), which does not belong to the oyster family at all, has a shell which is more nearly circular, a little convex, and sometimes a foot in diameter. They are found in Madagascar, Panama, Ceylon, East Indies, Australia, South Sea islands, Philippines, and the West Indies. Pearls are deposits of nacre formed about some foreign substance. Prof. Jameson has discovered? by investigation upon the sea-mussel that, in their case, pearls are caused by a parasitic worm (T7rematode). Pearls are collected by divers who go down from 6 to 8 fathoms for them. Hun- +“ On the coasts of Holland, Belgium, and France far greater care is taken of their species (Os’trea ed’ulis) than we take of ours (Os’trea virginia’na), but our natural conditions are superior to theirs.””-—Linville and Kelly, p. 169. ? Linville and Kelly’s ‘‘ General Zodélogy,”’ p. 173. 78 BRANCH MOLLUSCA dreds of vessels are engaged in this industry. Pearls of various shapes are found. Their colors may be white, yellow, pink, blue, red, green, or even Fig. 57.—Some enemies of the oyster: 1, Drill ( Urosalpinaz cinerea); 2, mussel (Mytilus edulis); 3, Sabellaria vulgaris; 4, periwinkle (Fulgur carica). (Report of Fish Commision for 1897.) black. Round lustrous white ones are most prized in Europe and America, but those of the yellowish hue are preferred by Asiaties. PELECYPODA 79 Fig. 58.—Section of Anodon’ta, showing the digestive tube: m, Mouth; g, gullet; U, liver; s, stomach; r, 7, intestine; a, anus; p, pericardium; k, kidney; s.c., chamber above the gills. (Furneaux.) Fig. 59.—Anodon/ta, lying in one valve, with upper lobe of the mantle removed: p, Pericardium; k, kidney; p.r., posterior retractor muscle; p.a., posterior adductor muscle; a.a., anterior adductor muscle; a.r., anterior retractor muscle; p.p., protractor pedis muscle; a, anus; e.s., exhalent siphon; 7.s., inhalent siphon; /.m., cut edge of the mantle; o0.g., outer gill- plate; m.l., mantle lobe; v.g., inner gill-plate; v, internal organs; f, foot; l.p., labial palps; l, liver; p.l., pallial line. (Furneaux.) Fresh-water mussels (Figs. 58, 59) or clams of our ponds, lakes, and streams have firm leaf-like gills and two nearly equal adductor muscles. SO BRANCH MOLLUSCA The siphon is incomplete and the pallial line is entire, that is, without sinus or indentation. The foot is long and compressed. The valves of the shell are held together by the strong adductor muscles, and opened, when these relax, by the elastic spring or hinge ligament. ‘The shells are a dull black on the outside, and pearly white, tinted with iridescent hues, on the inside. The shell of the Unio is not so large and strong as that of Anodonta, while the latter genus has no hinged teeth. Clams are found in ponds and large streams (which do not dry up in the summer), distributed along the direction of the strongest currents to insure food supply. They are partly buried in the mud, the open edge of the shell down and the valves slightly apart, with the fleshy foot protruding from the anterior ventral margin. When disturbed, the foot and edges of the mantle-lobes are retracted and the valves tightly closed. The shell is the mussel’s principal means of defense. It has many enemies besides man, such as the musk-rat, raccoon, mink, otter, and other mammals that live in and about the streams where the clam is found. Such animals as the musk-rat gnaw off the hinge ligament to get the shell open. The young clams are carried in the gills, and were formerly mistaken for parasites, and are called glochidea. They differ much in shape from the adult. The glochidea, or young clams, pass out through the exhalant siphon and attach them- selves by hooks on the valves to the gills or fins of fishes, by which they are protected from enemies and kept supplied with fresh water until suffi- ciently mature for independent existence, when they detach themselves from their host and drop to the bottom of the stream. The giant clam (Tridac’na gi’gas) of the tropics has a shell from 2 to 4 feet long, which may weigh from 300 to 500 pounds. The soft-shelled clam (My/a arena’ria) abounds in the mud flats of the Atlantic coast north of i Cape Cod. The young clams swim about on the Fig.60.—Tere’dona- surface of the water. After the shell appears, val/is, removed from its they sink to the bottom and attach themselves by calcareous tube, with the byssus. When the clam is about + inch long, elongated siphons. the byssus disappears and the animal buries itself (Quatrefages. ) in the mud. As it grows, it keeps enlarging and deepening its burrow until it may extend from 8 to 12 inches below the surface of the mud. The long siphons are extended up to within reach of the sea-water, whose currents bring to the clam food and air. The water enters through the ventral siphon, is driven through the gills, and finally passes out through the excretory tube, the dorsal siphon. Daaihen form much used for food is the ‘* Quahog ”’ (Venus mercenaria), which is characteristic of warmer waters, and is found from Cape Cod to Texas. It burrows a little way below the surface, but is often found with GASTEROPODA 81 its shell partly exposed. Along the Atlantic coast people use the Mya or Venus for their “ clam-bakes.”” Many hundred bushels are used every year for this purpose. The razor-shell clams have similar habits. They are concealed in vertical holes in the sand with the posterior end of the shell uppermost. They have a powerful club-shaped foot, and can dig so rapidly that unless one approaches very cautiously they escape from view. ‘They seem to be sensitive to light and to the “ jar ’’ made by approaching footsteps. The borer (Pho/las) has its brittle but very hard shell marked like a file, with which it bores into the hardest rocks. The united siphons are longer than the rest of the body. Some forms are phosphorescent, emitting bluish-white light. ‘The ship-worm (Tere’do) (Fig. 60), another borer, works into wood, doing much damage to ships in the tropics. The larva enters the wood when it is extremely small and enlarges the tunnel as it grows. The wood which it excavates is not used for food, but is carried off by the excretory siphon. Its food, which consists of microscopic organisms, is brought in by the currents. The amount of damage these borers do, seems incredible. They completely honeycomb the hull of a wooden vessel. The best protection against them is the sheathing of the hull with copper. Palmetto is the best resistant among woods. The ship-worms caused the destruction of a dam in Holland, threatening destruction to the country. Their dis- persal is wide, since they are carried all over the world in the floating wood which they attack. CLASS II. GASTEROP’ODA These are asymmetric, usually univalve mollusks, and the head region bears either one or two pairs of tentacles. As in the snail (Fig. 61), the eyes are borne either at the bases or at the Fig. 61.—A snail. (After Tenney.) tips of the tentacles. The shorter tentacles are probably organs of smell. The head contains the mouth, in which is the tongue, covered by the radula, a ribbon-like organ supplied with chitinous teeth and used for rasping the food. The manile is not divided into two parts as in the mussel, but unites around the neck, leaving but a small respiratory aperture 6 82 BRANCH MOLLUSCA into the mantle cavity. The foot is broad and flat and is used for locomotion. Respiration is accomplished through the wall of the mantle cavity, or by one or two plume-like gills or ctenidia in the mantle cavity. In the air-breathing forms there may be simply a pulmonary sac. The shell is a spiral, either flat or elongated (Fig. 62), and is usually closed by a flap or operculum (a horny plate growing on the posterior portion of the foot) for protection. apex Suture «<* whords forming the spzr2 . body whorl - aperture Fig. 62.—A snail shell. (Morse.) Some Gasteropods are marine, some are fresh-water forms, and still others are terrestrial. The limpets (Patel’lide) are uncoiled forms with open conical shells. They are found adhering to rocks between tide-marks. The foot acts as a sucker, enabling the animal to resist a force of a thousand times its weight when one attempts to detach it. The common limpet (Patella vulgata) is used as food. It feeds upon seaweeds. The ear-shells ( Haliot/ide), found on our western coast, have a row of perforations near the margin of the shell through which the tentacles pass to the exterior. The shells are much used in inlaid work on account of their beautiful iridescent color. They are also used as food, and the shells are used for making buttons. 1 The cowries (Cypre’ide) have richly enameled shells with small open- ings. They are beautiful and are sold for ornaments, some species being much prized. A beautiful yellow shell, an inch or less long, which abounds in the East Indies, is used as money in Siam and in parts of Africa: 6400 cowries are equal to about 36 cents. The cowries are tropical, but a few species are found in temperate seas. GASTEROPODA 83 The helmet-shells (Cassid’id@) are composed of layers of different colored material and are used for carving cameos. The tritons or sea conchs (7'riton’ide) have handsome shells, frequently more than a foot in length. The shells of one species is used by the South Sea Islanders as a trumpet. The T'riton’ide have a proboscis, a well-developed siphon, and a short foot. ° “The long, nearly cylindric shells of the Cavolinide make up much of the ‘ pteropod ooze’ of the deep seas.” The common periwinkle (Littori/na) (see Fig. 57, p. 78) abounds on the coast of New England and southward, where it is used as food. It is a native of Europe. It is a vegetable feeder, and is valuable in cleaning up the seaweeds from oyster-beds. The oyster drill ( Urosal’pinx ciner’ea) (see Fig. 57, p. 78) bores a hole through the shell of the oyster and feeds upon its soft parts. Natica is another drilling sea-snail common on our Eastern coast. It burrows in the sand for clams and bores a hole with its radula, rotating its own body in the action. The Nudibranchs.—In the Nudibranchs the shell is entirely absent in the adult. True ctenidia are replaced as breathing organs by a number of secondary branchiz, sometimes simple, sometimes branched processes or leaf-like tufts, which may be distributed over the dorsal surface (as in H’olis), or placed in a row on each side beneath the mantle-flap (as in Pleurophylli’dia). These soft naked sea-slugs live in shallow water near the shore, crawling about and feeding upon the seaweeds. Their protect- Ive resemblance is very great on account of both color and form. They move very slowly. This also aids them in escaping the notice of their enemies. The land snails and slugs (Pulmona’ta) are air breathing. The air enters the mantle cavity through a small opening which is near the right side in the deztral forms (that is, the spiral of the shell turns like the hands of a clock from left to right), and on the left side in the left-handed (sinis- tral) forms. Land snails ( Helic’ide) are common in moist woods. They come out at night or in cloudy weather to feed on succulent vegetation. When they are numerous they do much damage. They, in common with the pond snails, have thin spiral shells. They have two pairs of tentacles. The upper and larger pair bears the eyes at their tips, and the shorter pair is the organ of touch. ° (See Fig. 61, p. 81.) The land snail (Helix) has no operculum, and when frost comes it with- draws into its shell, fitting the opening to some smooth object, and secretes - a layer of mucus. This hardens upon drying and forms a tough membrane. the epiphragm, which closes the opening. In at least one species of Helix a small hole is found just below the lung aperture, through which an ex- change of gases may take place. As a rule, snails lay their eggs in strings or masses, but the land snails bury their eggs singly or deposit them thus in moist places. Snails are used as food, being even shipped to the United States from Europe. Land slugs (Limac’ide) are naked. The shell is vestigial and con- cealed by the mantle. They have a rasping tongue like the snail’s. The giant yellow slug of California (Ariolimaz californica) reaches a length of 12 inches. The Pulmonata are hermaphroditic. The garden snail hibernates by coiling up in its underground burrow in winter. Pond Snails.—The common pond snails have but one pair of tentacles, and the eyes are situated at the bases of these. They breathe by means 84 BRANCH MOLLUSCA of a lung-sac instead of by gills, and must come to the surface occasionally for air. In genus Physa the spiral of the shell is left-handed; in Limne’a, right-handed, and in Planor/bis the shell is discoid or a flat spiral. The eggs of genus Physa are deposited in gelatinous, transparent, oblong capsules of an inch or less in length attached to submerged sticks or leaves. Genus Limne’a lays the eggs late in spring in capsules sur- rounded by a mass of jelly. The young pass through a metamorphosis. Still other pond or river snails breathe by means of gills. They live in the bottom of ponds or streams and are carnivorous. CLASS III. CEPHALOPODA Class Cephalop’oda (head-footed) consists of such forms as the squid, cuttle-fish, octopus, and nautilus. They are all marine, and,inmanyrespects, the most highly developed of all mollusks. There is a distinct head, bearing a pair of large well-developed eyes, and surrounded by arms or tentacles which are modifica- tions of the anterior margins of the foot.!_ The posterior part of the foot is transformed into a funnel-like siphon. The body is bilaterally symmetric. Respiration is through gills which line the mantle cavity. The shell may be external, as in the nautilus; or internal, as the pen of the squid; or lacking, as in the octopus. They are usually carnivorous. Some are solitary, as the devil-fish; others, as the squid, go in Immense shoals. The senior author has seen acres of ground covered with the catches of them on the Pacific coast. The circulatory system is closed and consists of a somewhat complete heart and arteries, capillaries and veins. The principal ganglia are grouped about the esophagus. The nervous system is the most highly developed of any of the branch, consequently they are the most intelligent of all mol- lusks. They have the power of quickly changing color to harmonize with their environment. Cuttlefishes are rapid-swimming Cephalopoda living at a depth of several fathoms, but sometimes coming into shallower water. The cuttlefish has a distinct head bearing ten long arms, and a pair of highly developed eyes resembling those of a fish. The free end of the head bears the mouth. The inner surface of each arm or tentacle is flat and bears four longitudinal rows of suckers. The fourth pair of tentacles is much longer and more slender than the others, and the club-shaped end bears suckers. The 1See McMurrich, p. 341. CEPHALOPODA 85 body is covered by the thick integument of the mantle. The internal shell is calcareous and furnishes the cuttlebone used for canary birds. Cuttlefishes are carnivorous, feeding upon crabs, clams, or fishes. They delight in the daylight and in the open sea, so they need to be pro- tected from the view of their enemies. For this purpose they discharge an inky fluid to cloud the water so as to escape detection. The dark- colored secretion is carried in the ink-bag connected with the siphon. The ink was used in ancient times as a writing fluid. The sepia ink used by artists in making the sepia pictures is manufactured from this fluid of the cuttlefish. The cuttlefish is also used as an article of food in the Old World. Fig. 63.—Loli’go vulga'ris. (After Verany.) Squids (Fig. 63) swim in schools. They, unlike cuttlefishes, are noc- turnal. They are carnivorous, feeding upon young fishes. The common squid is a foot or less in length. The internal shell is a horny “ pen” shaped something like a feather, which is embedded in the dorsal portion of the mantle. By alternately taking water into the mantle cavity and forcing it out, the squid is driven rapidly backward. It avoids detection by its color changes and by an inky discharge like that of the cuttlefishes. It feeds upon small fishes and crabs, which it kills by biting with its power- ful horny beak. Its enemies are large fishes and man. Giant squids are over 9 feet long, with arms 20 or 30 feet in length. The octopus is another member of this class. It has a short subspherical body without any shell. It has eight sucker-bearing arms, with which it SO BRANCH MOLLUSCA Fig. 64.—The chambered nautilus. “‘Vear after year beheld the silent toil That spread his lustrous coil; Still, as the spiral grew, He left the past year’s dwelling for the new, Stole with soft step its shining archway through, Built up its idle door, Stretched in his last-found home, and knew the old no more. ““Thanks for the heavenly message brought by thee, Child of the wandering sea, Cast from her lap, forlorn! From thy dead lips a clearer note is born Than ever Triton blew from wreathed horn! While on mine ear it rings, Through the deep caves of thought I hear a voice that sings:— “‘Build thee more stately mansions, O my soul, As the swift seasons roll! Leave thy low-vaulted past! Let each new temple, nobler than the last, Shut thee from heaven with a dome more vast, Till thou at length art free, Leaving thine outgrown shell by life’s unresting sea.” Oliver Wendell Holmes. CEPHALOPODA S87 graspsits prey. ‘“‘ Devil-fishes”’ are found in all seas. They are gregarious when young, but the adult is solitary. They creep about among the rocks upon the extremities of their arms, generally moving sideways; or swim rapidly, either forward or backward. The arms are somewhat webbed at the bases. Some devil-fishes measure 12 to 15 feet, others but a few inches. They are found on our western coast and in the Pacific islands. They are much used for food along the Mediterranean Sea and by the Chinese and Italians of San Francisco. The Nautilus (Fig. 64).—This Cephalopod has a many-chambered, spiral, univalved shell, lined with pearly nacre, hence is often called the “pearly nautilus.” It has four gills instead of two. It crawls about on the sea bottom by means of its many (about forty) small tentacles. It has no suckers. The outer chamber of the shell is a large compartment in which the animal lives. As it grows, the nautilus partitions off the space behind it and meves forward. A calcareous tube containing the siphuncle, a slender tubular continuation of the body, extends through all the septa. The abandoned compartments are filled with air. The nautilus has a beak and a rasping tongue, like those of the squid. Each of its two disk-shaped eyes is attached by its convex side to a short thick stalk. The aperture of the eye is small, and there is no cornea, no iris, nor vitreous humor, but simply the retina at the base of a disk or pit. The nautilus has not the power of changing its color, and has no ink sac. It lives in the deep water in the south Pacific Ocean, and has been but little studied. Many of the species of former ages are extinct. This is the “chambered nautilus,’ immortalized by Oliver Wendell Holmes. Economic Importance.—Mollusks are probably of more direct use to man than any other invertebrate branch. The oyster industry is of vast importance, giving employment to thousands of persons and bringing an annual income of millions of dollars. Clams are also used extensively for food, and peri- winkles and snails less extensively. We get also pearls, and the mother-of-pearl for the making of buttons, knife-handles, and novelties. Factories have been established in Illinois and Iowa for making buttons on a large scale from the fresh-water mussel shell. This industry threatens to exterminate these bivalves unless means are taken to protect and perpetuate them. The squid is extensively used as bait in cod-fishing, while both the squid and the cuttlefish furnish the sepia ink used by artists. The cuttlebone used for canaries is another product of the cuttlefishes. The ship-worm does much harm to dikes, wharves, and piles, or any wooden structures which have been in water some time. Important Biologic Facts.—The mollusks are the most highly organized of any of the invertebrates except the Arthropoda, 88 BRANCH MOLLUSCA and many zodlogists place them above the Arthropoda. They have a well-defined circulatory system and nervous system and especially highly developed eyes. They usually have a metamor- phosis, some of the stages of which show indications of affinity with ‘‘worms.”’ Classification.— Class. Hxamples. Pél’/ecyp’oda. Sea-mussel, Oysters, Scallop, Fresh-water mussel. Gas’ terop’oda. Limpets, Periwinkle, Snails. Céph’alop’oda. Cuttlefish, Octopus, Nautilus. BRANCH ARTHROPODA ARTHROP’ODA may be characterized as animals having bi- laterally symmetric segmented bodies with jointed appendages and a chitinous exoskeleton. The segments of the body are not so numerous as in the worms. This branch includes a vast assemblage of animals which are widely distributed over the earth. They vary in habitat, being aquatic, terrestrial, subterranean, aérial, or some com- bination of these. Some are of direct use in furnishing food for man, as the lobster and the bee. Many cross-fertilize plants, and are thus of indirect use to man. As common examples of this branch may be named the lobsters, crabs, crayfishes, spiders, ‘“‘ thou- sand-legs,”’ and insects. The digestive system is between the circulatory system and the nervous system. It is not much coiled, but runs almost straight through the body. (See Fig. 69.) The circulatory system consists of a dorsal blood-vessel open at the anterior end. The blood is pumped forward. It fills all the irregular spaces of the body, through which it bathes all the tissues and makes its way back to the dorsal vessel. The corpuscles are colorless and ameboid. The respiratory system consists of gills in the aquatic forms, and of air-tubes or tracheze in the insects and other terres- trial forms. The nervous system consists generally of a double chain of ganglia, connected by a double nerve cord, running along the ventral side of the body. (See Fig. 69, N.) Weshould expect to find a pair of ganglia to each segment, but several ganglia may be united, as inthe crayfish, where there are thirteen well-marked ganglia, the three anterior ones uniting to form the so-called brain. Multiplication—The sexes are usually distinct. Multiplica- tion is generally by fertilized eggs. 19 0) 9 90 BRANCH ARTHROPODA CLASS I. CRUSTA’CEA As examples of this class may be named crayfishes, lobsters, crabs, and “ pill-bugs.”’ The body has a limited number of segments, about twenty in the crayfish. Each pair of append- ages is regarded as being attached to a different segment. The head and thorax are united and called cephalothorax. The chitinous covering, rendered hard by deposits of carbonate and phosphate of lime, is called the carapace. Respiration is by gills, or branchie, though some breathe through the skin. The appendages are biramous, as seen in the swimmerets of the crayfish. A typically developed appendage, as the third pair of swimmerets, consists of a main stalk (protopod) and two branches, the outer (exopod) and the inner (endopod). Several of the appendages lack some of these parts. The student should homologize the appendages and tell or demonstrate which ones have missing parts. The class Criista’cea is usually divided into two sub-classes, the En’tomés’traca and the Mdl'acés’traca, with several orders under each. Sub-class Entomostraca is composed of crustaceans with a varying number of joints or segments. They are usually small or microscopic. There is a metamorphosis, the first stage being the free-swimming nauplius. ‘‘Parthenogenesis occurs in many genera of Phyllocardia and Ostracoda.’”’—Sedgwick. Order I. Phyllép’oda are small aquatic crustaceans with segmented bodies and leaf-like appendages. The brine shrimp, fresh-water Branchipus, and Daphnia are examples of the order. Daphnia is shelled and looks like a very small clam. The animals of this order form an important part of the food of fresh-water fishes. The eggs of many species can resist the drought, which is a valuable means of perpetuating them in small streams which dry up in summer. Order II. Ostrac’oda are small crustaceans with apparently unsegmented bodies enclosed in a bivalve shell, as the fresh- water Cypris. The abdomen is rudimentary. There are only two pairs of thoracic appendages, two pairs of maxille, one pair of mandibles, one pair of antennz, and one pair of antennules. The antenne and antennules are used for locomotion. The CRUSTACEA 91 antennules are also provided with olfactory hairs. Many of this order are marine., Some, however, live in brackish or in fresh water. They live usually at the bottom of their aquatic habitat. Order III. Codpép’oda.—As examples may be named para- sitic fish lice and the fresh-water cyclops. Respiration takes place over the entire body surface. The Cyclops (Fig. 65) is a small, white, shelless animal with elongated segmented body. It has a rather large eye in the center of its head. Order IV. Cirripe’dia or Barnacles. —These fixed, marine, shelled crusta- ceans are very abundant along the seacoast, the rocks being covered with them in places. Their food consists of small animals in the water. One may see thousands of barnacles snap- ping their food as the waves and tides dash over them. Some forms attach themselves to crabs, mollusks (Fig. 52), or even to whales, while others are true external parasites, sucking the juices of the ani- mals to which they are attached. The parasitic forms are extremely degenerate. Since they have no power of loco- motion by which to escape their ene- ‘ mies, the barnacles (Fig. 66) are pro- eee. ue: tected by shells capable of ‘‘ complete f, eggs. (Clark.) closure.’”’ The body is flexed ventrally and bears six pairs of cirri, which are used in straining small organisms from the water and in carrying them to the mouth. The mouth is surrounded by a pair of mandibles and two pairs of maxille. Barnacles are hermaphroditic, but cross-fertiliza- tion may occur. They have a metamorphosis, having first a nauplius and then a cypris stage, the latter developing into the fixed adult (Fig. 67). This order furnishes a good illus- tration of the principle that inactivity leads to degeneration. 92 BRANCH ARTHROPODA The barnacles (Lepas) are found in clusters on the bottom of ships and often greatly impede their progress. Fig. 66.—Anatomy of Lepas fascicularis (Packard): A, c, Six pairs of legs or cirri; f, filamentary appendages; m, mouth; s, stomach; h, openings of the liver (/) into the stomach, which is represented as laid open; 7, in- testine; a, vent; t, testis; v, vasa deferentia, one cut off; p, male appendage; 0, ovary; e, adductor muscle connecting the two basal valves; vs, scutal valve; vc, carinal valve; vt, tergal valve. Enlarged twice. B, 1, Palpus; 2, mandibles; 3 and 4, first and second maxille. C, Nervous system: s, Brain, sending the optic nerves to the rudimentary eye (e), each optic nerve having an enlargement near the eye, 7. e., the ophthalmic ganglion (0); between o and a are the nerves which go to the peduncle; a, nerve sent to the adductor scutorum; @, commissure between the supra- and infra-esophageal ganglia (7); c, c, c, c, c, c, nerves to each of the six feet. Enlarged four times. (After Kingsley.) Sub-class II. Mal’acés’traca is composed of crustaceans of a definite number of segments, usually twenty—the head of five segments; the thorax, eight; and the abdomen, seven. ‘These CRUSTACEA 93 segments are sometimes so fused as to puzzle one to distinguish twenty segments, as in the crayfish, but by regarding one pair of appendages to each segment one is able to count the number of segments present in the specimen. There is a number of orders under this sub-class, but only a few can be mentioned. Order I. Phyllocar’dia is marine. The genus Nebalia, with its bivalve carapace, its leaf-like thoracic feet, and biramous eae hh { ; 4 Fig. 67.—Three adult crustaceans and their larve: a, Prawn (Peneus), active and free living; b, larva of prawn; c, Sacculina, parasite; d, larva of Sacculina; e, barnacle (Lepas), with fixed quiescent life; f, larva of barnacle. (After Hackel.) (From Jordan and Kellogg, ‘ Animal Life,” D. Appleton and Co., Publishers.) abdominal appendages, may be taken as an example of this order. Order II. Décap’oda.—This order consists of both marine and fresh-water crustaceans. It contains the best-known forms as well as the most useful ones to man, as the crayfish, lobster, shrimp, prawn (Fig. 67), and crab. As the ordinal name sug- 94 BRANCH ARTHROPODA Vox l (ee 5 Au Fig. 68.—Astacus fluviatilis. Ventral or sternal views (nat. size). A, Male; B, female: a, Vent; gg, opening of the green gland; /b, labrum; mt, metastoma or lower lip; od, opening of the oviduct; vd, that of the vas deferens; 1, eye-stalk; 2, antennule; 3, antenna; 4, mandible; 8, second maxillipede; 9, third or external maxillipede; 10, forceps; 11, first leg; 14, fourth leg; 15, 16, 19, 20, first, second, fifth, and sixth abdominal ap- pendages; x, x1, xiv, sterna of the fourth, fifth, and eighth thoracic somite; xvi, sternum of the second abdominal somite. In the male, the 9th to the 14th and the 16th to the 19th appendages are removed on the animal’s left side; in the female, the antenna (with the exception of its basal joint) and the 5th to the 14th appendages on the animal’s right are removed; the eggs also are shown attached to the swimmerets of the left side of the body. (Huxley.) CRUSTACEA 95 gests, they have ten “ feet.’”’ The first pair is very large and armed with large strong pincers or chelw, for defense or for securing their prey. Their eyes are on movable stalks and can be withdrawn under the rostrum or beak for protection. The anterior thirteen segments are covered by a chitinous calcareous shield called the carapace. The Crayfish (Fig. 68) is the best known inland example of this order. The twenty segments may be discerned by counting one segment to each pair of appendages, which are arranged in the following order: one pair of antennules, one pair of antennz, one pair of mandibles, two pairs of maxille, three pairs of maxillipeds, five pairs of legs, six pairs of swim- D Aa Va ¢ T SS Fig. 69.—Longitudinal section through Astacus fluviatilis: C, Heart; Ac, cephalic aorta; Aa, abdominal aorta; the sternal artery (Sta) is given off close to its origin; ‘Km, masticatory stomach; D, intestine; L, liver; T, testis; Vd, vas deferens; Go, genital opening; G, brain; N, ganglionic cord; Sf, lateral plate of the caudal fin; 0, eye stalk. (Huxley.) merets, or nineteen pairs of appendages and a terminal segment without appendages, called the telson, which contains the vent or posterior opening of the alimentary tube. Its locomotion on four pairs of legs may be forward, sideways, or backward. Its backward locomotion by its “ tail fin” is probably its best and most rapid mode of locomotion. Digestion.—The food is seized by the cheliped and may be conveyed directly to the mouth, or, after being torn into bits, may be transferred to the pincers of the second and third pairs of legs and from there to the mouth. The jaws move from side to side instead of up and down. From the mouth the food passes into the esophagus, which is very short, as the stomach is in the head (Fig. 69). In the inner walls of the stomach 96 BRANCH ARTHROPODA are three “‘ teeth” or hard processes which are controlled by muscles attached to them and to the carapace. By the action of these muscles the food is ground between these teeth, which are sometimes called the “gastric mill.’ In the poste- rior part of the stomach there is a series of filaments or stiff hairs which prevent any coarse or unground food from passing into the intestine. So the stomach is a masticating rather than a digestive organ. When the food is ground fine it passes into the intestine, a straight tube extending from the stomach to thevent. Thefood is acted upon by the digestive fluids from the glands which lie on each side of the stomach and whose ducts enter just back of the stomach. Digestion and absorption take place in the intestine. Circulation.—When the heart (Fig. 71) contracts the blood flows both forward and back- ward. Five tubes, or “‘ arteries,” Fig. 70.—Astacus fluviatilis. A male specimen, with the roof of the carapace and the terga of the ab- dominal somites removed to show the viscera (nat. size): aa, Antennary artery; ag, anterior gastric muscles; amm, adductor muscles of the mandibles; cs, cardiac portion of the stom- ach; gg, green glands; h, heart; hg, hind gut, or large intestine; Lr, liver; oa, ophthalmic artery; pg, posterior gastric muscles; saa, superior abdominal artery; t, testis; rd, vas deferens. (Huxley.) carry it forward, and two, backward. These ‘ arteries ”’ keep ividing until they form minute capillaries with open ends. The blood runs into the irregular body spaces, or sinuses, and CRUSTACEA 97 bathes the tissues, then goes into the larger median ventral sinus below the thorax and abdomen, from which it is conducted to the gills. After being conveyed to the gill filaments, where it is aérated, it is returned to the heart through the pericardial sinus. The blood enters the heart, or dorsal vessel, through three pairs of openings, one on each side, a pair on the top, and another pair below. Valves prevent the blood from returning through these openings. Mga Heat Zi AA HS | : - } Fig. 71.—Astacus fluviatilis. The heart (x 4). A, From above; B, from below; C, from the left side: a.a., Antennary artery; a.c., ale cordis, or fibrous bands connecting the heart with the walls of the pericardial sinus; b, bulbous dilatation at the origin of the sternal artery; h.a., hepatic artery; l.a., lateral valvular apertures; 0.a., ophthalmic artery; s.a., superior valvular apertures; s.a.a. superior abdominal artery; st.a., sternal artery, in B cut off close to its origm. (After Huxley.) Respiration—TVhe plume-like gills are attached to the basal joints of the legs. They are situated in partially closed chambers between the body wall and the carapace. The water is drawn in and out by the “ gill-bailers,” parts of the second maxille, in their vibration back and forth. In passing over the gills the water is separated from the blood by an extremely thin membrane. Through this membrane the carbon dioxid is thrown off and oxygen taken into the blood. Nervous System.—Several ganglia unite to form the supra- a 98 BRANCH ARTHROPODA esophageal ganglion or “ brain,’’ from which a nerve cord passes on each side, uniting below the esophagus in a double (apparently single) ventral nerve cord (Fig. 69), which ex- tends the whole length of the body and connects the ganglia. We should expect to see a ganglion for each segment, but there are but thirteen ganglia, some of these being formed from a union of several. On each side of the esophagus is a large gang- lion; there are five more ganglia in the thorax and six in the abdomen. The stalked eyes are compound, being composed of many facets. The sense of touch is well developed. The surface of the body is sensitive and the antenne are especially adapted for “ feelers.”’ The sense of smell is thought to be seated in the hairs or setz on the antennules. Multiplication.—In the spring the little brown or black eggs may be found attached to the swimmerets of the female. For some time the young crayfishes, by means of hooks on their claws, cling to the swimmerets of the mother for protec- tion. Molting.—The young crayfish, which is of much the same ap- pearance as the adult, grows rapidly. Since the shell is hard the animal cannot enlarge except when it sheds its skinor molts, which it does periodically. Even the hard lining of the stomach is cast. Growth takes place while the new skin or shell is form- ing. Restoring Lost Parts.—Crayfishes have the power of growing a new leg to replace one broken off by accident or in a fight. This accounts for the unequal size of the chelipeds in many specimens. Habits.—Crayfishes inhabit fresh-water streams and ponds, lurking under stones or ledges in daytime and feeding at night. When the streams dry up, they dig holes in the ground until they reach water. These are sometimes many feet deep. The clay dug out around the hole is deposited in a “ chimney.” In these holes they probably live till the next spring. Some species do not live in the water, but burrow in the soft moist earth, and one species has been found in the sea. Crayfishes are omnivorous, eating anything they can get, but they prefer worms, insect larvee, and snails. CRUSTACHA 99 The protective resemblance is excellent, the colors varying from a delicate pink or tan to a dark green or purple. Use.—Crayfishes are used by the million in France, and to a limited extent in the United States, for food. They also furnish food for fishes. Raccoons, muskrats, and crows prey upon them. The lobster (Fig. 72) is marine and is very much like the crayfish, only much larger. Specimens weighing twenty-five Fig. 72.—A small lobster (dorsal view) mounted on a glass so as to show both dorsal and ventral views. Students’ work. pounds have been captured. Among the invertebrates the lobster ranks next to the oyster as an article of food for man. Prawns and shrimps look like our common crayfish and are used to some extent for food. They are small. The common prawn (Palemone’tes vulga’ris) is about 2 inches long. It is transparent, so that the viscera can be seen through the thin leathery carapace. 100 BRANCH ARTHROPODA Hermit Crabs (Fig. 73).—There are a number of species of hermit crabs which are not true crabs, but are more like the lobster and crayfish. They have the habit of backing into empty univalve shells which they carry about with them and into which they may withdraw for protection. This habit has resulted in a soft-skinned, reduced abdomen, with a spiral twist and with no appendages except a pair of hooks for hold- ing on to the inside of the shell. The abdomen is always hidden in the shell. The head, thorax, and legs project when the animal is active, but are withdrawn when danger approaches. Fig. 73.—Hermit crab (Pagu’rus) in shell, with a sea~-anemone (Adam’sia pallia’ta) attached to the shell. (After Hertwig.) (From Jordan and Kel- logg, ‘‘ Animal Life,’’ D. Appleton and Co., Publishers.) As it grows it discards its shell and hunts a larger one. Some of these hermit crabs have a peculiar commensal life with cer- tain sea-anemones (Fig. 73), which they carry about on their shells. If the sea-anemone becomes detached the crab hunts another and places it on its shell. The crab is protected from its enemies by the stinging threads of the anemone, also by its resemblance to the seaweed, while the anemone is assured of a fresh food supply by being carried from place to place by the crab. Crabs are other examples of this order. The cephalothorax CRUSTACEA 101 is much broader than that of the crayfish, and the abdomen, which is used only to protect the eggs of the female, is folded under the cephalothorax. They are great scavengers. Many kinds are used as food. One of the best for this purpose is the Fig. 74.—Successive stages of the molting of one individual of the blue crab, Calli’nectes sa’pidus. (G. Hay, in Doc. 580, Bureau of Fisheries.) edible or “blue crab” (Callinectes sapidus), great numbers of which are caught along the Atlantic and Gulf coasts. They are best liked for food just after their molting (Fig. 74), and are then called ‘ soft-shelled crabs.’ They are 102 BRANCH ARTHROPODA ”) sometimes called ‘‘ swimming crabs’”’ because they have the last pair of thoracic legs flattened and paddle-like, adapted for swimming sideways quite rapidly. They have large sharp lateral spines. The strong chelipeds are adapted for cutting. Each of the other thoracic appendages ends in a point with no forceps. The little ‘‘fiddler-crab” lives in salt marshes along the Atlantic coast. The male has one big and one little cheliped, which he brandishes grotesquely when disturbed. The spider crab (Macrochei’ra) of Japan sometimes measures from 12 to 16 feet from tip to tip of legs, but the body is only a few inches—about a foot—in width, making them very peculiar creatures. At a little distance they look like immense sprawling spiders. The little oyster crab, found so often in our dish of oysters, does no harm to the body of the oyster, but its life within the shell insures its food being brought to it by the currents of water made by the oyster to bring its own food. This is a case of commensalism! where there is a decided advantage to one animal and none, so far as known, to the other, yet the intruder does no harm. Order III. Arthrés’traca comprises both marine and fresh- water forms. The first thoracic segment, and sometimes the Fig. 75.—Beach flea, Gam’marus orna’tus. (After Smith.) second, is fused with the head and bears maxillipeds. The eyes are usually sessile. Gammarus (Fig. 75) is a fresh-water form. The Pill-bug.—If one searches under old boards or logs he will find a small gray or brownish fourteen-footed crustacean, truly terrestrial, with depressed body and with gills on the ab- dominal appendages. It is called “ pill-bug”’ from its habit -.1See Jordan and Kellogg’s “ Evolution and Animal Life,” p. 370. ARACHNIDA 103 of rolling up into a ball when surprised. Its protective resem- blance is good. Its locomotion is by crawling or running. Some of the marine Arthrostraca are parasitic on crabs and in the mouths of fishes. CLASS II. ARACH’NIDA Arachnids are arthropods with the head and thorax generally fused into a cephalothorax, bearing six pairs of appendages. The first and second pairs are for biting. Then follow four pairs of walking legs. There are no antenne, the eyes are simple, and the abdomen is apodal.! The abdomen varies much. It is short in the spiders, long in the scorpions, or is fused with the thorax, forming a stout body in the mites. They are usually oviparous. How- ever, some scorpions and some mites are viviparous. They are generally terrestrial, but some live in the water. There is no well-marked metamorphosis. Order I. Scorpion’ida.—Scorpions (Fig. 76) are arachnids with long slender bodies ending in a poison fang. The head and thorax’ are fused and bear several pairs of jointed appendages. The abdomen consists of a broad anterior and a narrower posterior portion. There are several pairs of eyes. Respiration is by means of four pairs of lung-sacs opening on ventral side of abdomen from the third to sixth segments. Food.—They are carnivorous, feeding upon spiders and in- sects, which they seize with their pincers and sting to death. Multiplication —They are viviparous. The mother cares for the young with great solicitude, carrying them about at- tached to her body. Fig. 76.—Carolina scor- pion (Bu’thus carolinia’nus). 1 See Glossary. 104 BRANCH ARTHROPODA Size.—One giant species in Ceylon is 12 inches in length, while American species are about 4 inches long. Habits and Distribution.—Scorpions are nocturnal. They live in tropical and subtropical countries. Their sting is dreaded by man, but seldom proves fatal. About twenty species are found in North America. Order II. Phalangid’eax—The members of this order look like long-legged spiders, with small bodies. Closer observation shows that the abdomen is fused with the thorax and not F Fig. 77.—Parts of a spider. 1, Under part of a spider’s body: t, Thorax, or chest, from which the eight legs spring, and to which the head is united in one piece; f, fangs; p, palpi, or feelers, attached to the Jaws; a, abdomen; b, breathing-slits; s, six spimnerets with thread coming from them. 2, Front of spider’s head: e, Eyes; p, palpi; l, front legs; h, hasp of fangs; f, poison-fangs; j, outer jaws. (From Holder’s “ Zodlogy,’’ American Book Co., Publishers.) joined by a pedicel, as in the spiders. The “ harvest-man ” or ‘‘ daddy-long-legs’’ is a familiar example. It frequents shady places and feeds on small insects. They are a dull color, to fit their environment. So long as they remain motionless their protective resemblance conceals them very effectively from their enemies. The respiration is by trachez. Order IIL Arane’ida, or Spiders (Fig. 77).—These are arachnids with unsegmented abdomen joined by a pedicel to the thorax. ARACHNIDA 105 Appendages.—There are two pairs of mouth-parts. The mandibles or cheliceree are strong and composed of two por- tions, the basal falx and the sharp-pointed fang, in which is a small opening, the outlet of the poison gland. The palpi are Fig. 78.—The bird-spider (Myg’ale avicular'ia) capturing a humming-bird. (From Holder’s “ Zoélogy,” American Book Co., Publishers.) long and limb-like and are often mistaken for a fifth pair of thoracic legs. The basal joints are broad and adapted for chewing the food. They are called the maxille. Then follow four pairs of seven-segmented legs used for locomotion. The spinnerets on the abdomen are homologous to paired appendages. 106 BRANCH ARTHROPODA Color.—Almost all spiders are covered with hair. The color is partly in the skin and partly in the hair. The most common colors are grays and browns, but the colors are very varied, and in some species, as the jumping spider, they are almost as bright and gorgeous as those of butterflies. Foods and Feeding.—They are generally carnivorous, sucking the juices from their prey. Some spiders spin webs, others do not. The spider’s thread is composed of many fine threads, each passing from the body by a separate tube and then unit- ing. The united thread forms a cord finer than the finest silk of the silkworm, hence it is often used for the “ cross-hairs ”’ of the telescope. Respiration is by lungs or lung-sacs containing bookleaf- like plates, and by trachee. Senses.—The sense of sight is well developed, but they seem to be shortsighted, seeing clearly only at a distance of 4 or 5 inches. The palpi are organs of touch. Dimorphism.—Male spiders usually have longer legs and smaller bodies than the females. Sub-order Tét’rapnea’mones.—These spiders have four lungs and eight eyes. The most important members of the group spring upon their prey, often catching mice and small birds (Fig. 78). The large, dark, hairy spiders (Myg’ale) found in bunches of bananas belong here. The claws of the mandibles or jaws work up and down instead of from side to side. The trapdoor spiders (Ctenz’za) of the Southwest dig tunnels in the soil, line them with silk, and cover them with a close- fitting hinged lid. Sub-order Dipneu’mones.—The members of this sub-order have two lungs and a pair of trachee. This group includes the majority of living spiders. The ground spiders (Dras’sid@) do not spin a web, but hunt their prey at night. Many species make silken tubes in which they lay their eggs or hide when molting or in winter. An eastern species lives in a bag of silk hidden under stones. The tube-weavers (Clubion’idw).—These are also species which spin no web. In summer they live in flat tubular nests on plants, sometimes in rolled leaves. In winter they live in tubular nests under bark and stones. The Funnel Web Weavers (Agalen’idw)—They weave a concave sheet of silk with a funnel-like tube on one side, and with threads extending in ARACHNIDA 107 all directions attached to blades of grass for support. In the morning dew these webs form a shimmering silken sheet. The spider runs about on the upper surface of the ‘‘ sheet ”’ and catches any insects which light upon it. The tube or hiding place opens below, so that the spider can escape if an enemy appears upon the web. These are long-legged brown spiders, of which the common grass spider is a familiar example. The ‘‘curled-thread weavers” are of two kinds, those which spin regular webs and those which spin irregular webs. The curled thread is composed _of silk spun from a special organ, the cribel’lum, in front of the spinnerets. It is combed into shape by means of stiff hairs called the calamis’trum on the metatarsus of the hind legs, as the spider moves the hind legs rapidly back and forth. ’ Those spiders which spin irregular curled threads (Dictyn’idz) usually make variously shaped webs on fences, under stones, in rotten logs, or upon plants having clusters of small flowers like the golden-rod. There are but two genera of these spiders which spin regular webs (Ulobor’idz). The “trianglespider ”’ is found all over the country in pme woods. Its web is usually stretched between the twigs of a dead branch of pine or spruce, and consists of four plain radiating lines and a series of double cross-lines. The spider, which rests near one of the twigs from which a strong line is drawn to one of the other twigs, pulls the web tight, so that the cross-lines are separated as far as possible. When an insect lights upon one cross-line the spider suddenly lets go, so that the whole web springs forward and the insect becomes tangled up in the other cross-lines. The cobweb weavers (Theridi’ide) build their webs, which are ap- parently only a shapeless maze of threads, in the corners of rooms—as the house spider—or out in the fields between the leaves of bushes, or in the fence corners, or among rocks. They are generally rather light colored, small, and soft. They live in their webs, hanging by their feet, with the back downward. The cocoons, several of which are made in one season, are soft and round and hang in the web. The orb weavers (Epei’ride) construct some of the most wonderful homes built by any animal. First, there is an irregular outer framework of supporting lines; then there is a number—from twelve to seventy—of dry and inelastic lines radiating from the center. There is an inner spiral of these inelastic threads which begins at the center and winds outward. The rings of this spiral are about as far apart as the spider can reach. Its use is merely for support. The spider then begins at the outermost part of the web and spins an outer spiral of sticky elastic threads, winding inward, the concentric circles being close together. As it becomes neces- sary, in forming this outer spiral, the threads of the inner spiral are de- stroyed. When an insect touches one of the outer sticky threads the thread not only sticks to it, but it stretches so that the insect becomes tangled up in the other circles, which is all the easier to do since the threads are so close together. Many species strengthen the web by spinning a zigzag ribbon across the center. The making of the entire web seems to be done alto- gether by feeling and can be done in the dark as well as in the daylight. Most of the orb-weaving species have large, nearly spheric abdomens and stout legs, sometimes “‘ with humps and spines.” These spiders are often brightly colored, the colors of the abdomen being arranged in a triangular or leaf-shaped pattern. Some species live near the center of the web, hanging head downward, others hang back downward near one edge of the nest. In some species the male is smaller than the female. 108 BRANCH ARTHROPODA The crab spiders (T’homis’id@) are so-called because of their short broad form and peculiar habit of walking sidewise or backward. ‘ They spin no webs, but lie in wait for their prey.”! Some brightly colored species conceal themselves in flowers. Their protective resemblance is so good that insects visiting the flower often light within reach of the spider before seeing it. They live about plants and fences and hibernate in winter under stones and bark. The jumping spiders (At’tid@) have stout bodies and short legs, bright colors, and conspicuous eyes. They jump quickly sidewise or backward for a long distance. They make no webs except those in which they hiber- nate or lay their eggs. The Running Spiders (Lycos’ide)—These are the familiar hairy dark- colored spiders found under stones and logs. They depend upon their speed for the capture of their prey and run very swiftly. They resemble in appearance and habits the so-called tarantulas of the Southwest, but are smaller. The claws of their mandibles move horizontally. Their eyes are Fig. 79.—Female spider with young ones. (Cooper.) of different sizes. Some of these spiders build tubular nests in the ground and line them with silk. They sometimes conceal the entrance with leaves and sticks. They often drag the egg-sac, a large gray ball, after them. In genus Lyco’sa the young (Fig. 79) climb upon their mother’s back. The female of another genus, Dolome’des, carries the egg-sac ‘in her mandibles until the young are ready to hatch, when she fastens the sac in a buSh and spins a web of irregular thread about it in which the young remain for a time.” Order Acari’na.—These arachnids have stout bodies, there being no apparent segments, the abdomen being united with the cephalothorax. There is no heart nor blood-vessels. The res- piration is performed by means of tracheze. They are generally oviparous; some are viviparous. Many are parasitic (Fig. 80). 1 Comstock. ARACHNIDA 109 The mouth parts are more or less united to form a beak. The common red mite sucks the juices of the house plants which it Fig. 80.—The chicken mite (Dermanys’sus galli’ne): a, Adult; b, tarsus; c, mouth parts; d and e, young. All much enlarged. (Osborn, U. 8. Bu- reau of Ent., 1907). Fig. 81.—Cattle tick (enlarged). (After Salmon and Stiles.) infests. One mite (Dem/’odez) is parasitic in the hair-follicles of the dog, cat, sheep, cow, horse, and man. Another mite 110 BRANCH ARTHROPODA (Sarcop’tes scab’et) is the itch mite, causing the disease called the itch. Still another is called the cheese-mite. Ticks (Ixo’des) are parasitic, blood-sucking Acarina which attack man and other mammals. They do not exceed a centi- meter in length, the males being the smaller. The so-called “Texas fever” of cattle is transferred by the common cattle tick (Fig. 81). | | | | 4 Fig. 82.—Horseshoe or king crab (slightly damaged on left). (From specimen.) Order IV. Xiph’osu’ra.—The Lim/’ulus, or horseshoe crab (Fig. 82), is a marine arachnid living on the bottom of the sea in. shallow water, creeping along in the mud and sand and feeding MYRIAPODA EE: on worms. The body has a chitinous covering. The cephalo- thorax is arched and bears the large compound eyes and two simple eyes. The abdomen is almost hexagonal and ends in a long caudal spine. On the ventral side of the cephalothorax are six pairs of appendages, used for securing food and for locomotion. The last pair, the operculum, is broad and leaf- like and covers the five pairs of leaf-like branchial appendages of the abdomen. These appendages are for respiration. The shape of the body, its hard covering, marginal spines, and its color, which harmonizes with its environment, afford it ample protection and defense. There are several other orders, but these will suffice for our purpose in the present work. CLASS Tl. _MYRIAP’ODA The name indicates myriad footed, hence the common name, thousand-legs. A myriapod is a worm-like tracheate arthropod with a distinct head, a round or flattened body composed of many similar segments, to each of which is attached one or two pairs of appendages. Myriapods have one pair of mandibles, one pair of antenne, and numerous ocelli. ‘“‘ A few species are injur- ious to agriculture, while others are to be classed among our friends.” Order I. Chilop’oda—These are myria- pods with the body flattened, with fifteen to one hundred and seventy or more seg- ments, each bearing a single pair of legs, and with long, many jointed antenne (Fig. 83). The mouth parts are adapted for bit- ing. The opening of the poison gland is on the first pair of legs, which are used with the mouth parts. This order includes the centipedes, as Litho’bius, common under _. ; stones. The bite of the true centipede LN Sree gen (Scolopen’dra) is fatal to insects and to other small animals, their prey, and painful or even dangerous to man. ILI, BRANCH ARTHROPODA Order II. Diplop’oda.—These are myriapods with dorsally convex bodies. Each apparent segment, beginning with the fourth or fifth, bears two pairs of appendages. There are no poison fangs. The antenne are short and few jointed. This order includes the millipeds. An example is Julus. They are found under old stumps or about rotten logs. Their food consists usually of decaying vegetable matter, but some forms Fig. 84.—Class collecting insects. feed upon growing plants, otherwise they are harmless. They have a habit of rolling up into a helix-like coil when disturbed. They are bisexual. When hatched the young have but three pairs of legs. “‘ By successive molts new segments and append- ages are added ” until the adult form is reached. CLASS IV. INSEC’TA This class of Arthropoda comprises a very large number of species. Three hundred thousand, according to Kellogg, are known. INSECTA ite Habits and Habitat.—Insects vary in their habitat. Most of them are terrestrial, some are aérial, others are aquatic, a few even being marine, while still others are subterranean. Labrum (GS) Tarsus Sx ee O @ Q oy Tibia Maxilla \ vi ed yy Femur x Gox Trochanter > & {3 1 ( B Dochattine LS Mesothorax qo Scoutel Ss) —————— ey £ eS a o Meal SE at — ==. } o Wal e of» = Hind Wing ona Abdomen Sfernife A so relished by ants (p. 179) “is now known to be an excretion from the intestine issuing in fine droplets or even spray from the anal opening.” It is sometimes produced in large quantities, so that the leaves below the plant lice are coated with it and the walks beneath the trees spotted by it. It is fed upon by bees and wasps as well as by ants. In addition to the “honey-dew,” many species secrete another fluid, which is excreted as a liquid through ‘ various small open- ings scattered over the body.” This liquid soon hardens into a wax. The total waxy secretion appears as a mass of felted threads or wool, as in the wooly apple aphis, and probably serves as a protection for the soft, defenseless body. The aphids are remarkably variable as regards their reproduction sexually or agamically,? and as regards their possession of wings, so that the life- history varies not only in different species, but in the same species under different conditions. The eggs are laid in the fall, and from them hatches, in early spring, a colony of wingless individuals which may produce (without pairing) either living young or eggs. This may continue under favorable food supply ‘and temperature for a number of generations. Slingerland, of Cornell University, reared four generations of wingless ‘ agamie ”’ aphids. At any time, especially if food becomes scarce or other conditions unfavorable, winged individuals are likely to appear and fly away to other host plants, where they produce, agamically, new colonies. If temperature becomes low or other unfavorable conditions occur, these asexual individuals produce a brood consisting of both males and females. ‘‘ The males may be either winged or wingless, but the females are always wingless.’’ These sexual forms pair and produce one or more large fertilized eggs which lies dormant over winter and hatches into a wingless “ stem-mother ”’ in the spring, and a series of agamic generations follow. The multiplication of aphids is so rapid that, were it not for predaceous insects, such as lady- bird beetles, aphis-lions, and parasitic Hymenop’tera, and for insect-loving birds (see Birds), they would utterly destroy their host plant and ulti- mately starve themselves. Professor Forbes made an estimate of the rate of increase of the ‘ corn-louse,”’ and found that if ‘ all the plant-lice de- scending from a single ‘ stem-mother ’ were to live and reproduce through- out the year we should have coming from the egg the following spring 9,500,000,000,000 young. As each plant-louse measures about 1.4 mm. in length and 0.93 mm. in width, an easy calculation shows that these possible descendants of a single female would, if closely placed end to end, form a procession 7,850,000 miles in length.” Aphids vary sreatly in their feeding habits, many feeding upon the juices of tender leaves, stems, leaf-buds, or blossom-buds, while others suck the juices of tender roots in the soil, and sometimes the same species lives both above and below ground. Above ground they may be fought by strong solutions of soap, by kerosene emulsion, or by a weak solution of nicotin. Since they suck the juices of plants they cannot be affected by poisoning the food. Underground, carbon bisulphid is sometimes used, 1 Comstock. 2 Glossary. HEMIPTERA 145 but about the best remedy is to destroy the infested tree or vine, and plant one of another species which is not a host-plant for the pest. Fig. 114.—Phylloze’ra vasta’trix: a, Leaf with galls; b, section of gall showing mother louse at center with young clustered about; c, egg; d, larva; e, adult female; f, same from side. (a, Natural size; b-f, much enlarged). (Marlatt.) Fig. 115.—Phylloze’ra vasta’'trizx: a, Root-galls; b, enlargement of same, show- ing disposition of lice; c, root-gall louse, much enlarged. (Marlatt.) The grape Phylloxe’ra (Fig. 114) is a native aphid found upon the wild grapevines of the eastern United States. It was introduced into the south of France before 1863 upon rooted vines sent from America, and, 10 - 146 BRANCH ARTHROPODA curiously enough, says Kellogg, ‘‘came to California—in which state it has done much more damage than elsewhere in our country—from France, in- troduced upon imported cuttings or roots”’ (Fig. 115). Probably not less than 30,000 acres of vineyards have been destroyed by it since it was first noticed in 1874. ‘‘ The Phylloxera appears in four forms: (1) the gall form, living in little galls on the leaves (Fig. 114), and capable of very rapid multiplication (this form rarely appears in California); (2) the root form (Fig. 115), which is derived from individuals which migrate from the leaves to the roots, and which by the piercing of the roots, sucking the sap, and producing little quickly decaying tubercles on the rootlets, does the serious injury; (8) the winged form (Fig. 116), which flies to new vines and vineyards and starts new colonies; and, finally, (4) the sexual forms, Fig. 116.—Phylloxe’ra vasta'trix: a, Migrating stage, winged adult; 6, pupa of same; c, mouth parts with thread-like sucking sete removed from sheath; d and e, eggs showing characteristic sculpturing; all enlarged (Marlatt.) male and female (Fig. 117), which are the regenerating individuals, ap- pearing after several agamic generations have been produced.” The gall stage may be omitted, and the individuals hatched from the fertilized eggs go directly to the roots. The gall form can be prevented by spraying to kill the winter eggs. But about the only real cure for the infested roots is to dig them up and burn them and plant out resistant vines. The wild vines of the Mississippi Valley have evolved with the Phylloxera, and are capable of living and growing in spite of the pests. The French vine- yards, as well as those of California, are being renewed by grafting French stocks upon the resistant roots, thus rendering the vines practically im- mune. There are many species of aphids, but this example must suffice for our present work. Scale-bugs, mealy-bugs, and others (Coc’cide@) compose a very anomalous HEMIPTERA 147 group, the species differing greatly in appearance, habits, and metamor- phoses from those of the most closely allied families, and even the two sexes Fig. 117.—Phylloze’ra vasta’trix: a, Sexed stage larviform female, the dark-colored area indicating the single egg; b, egg, showing the indistinct hexagonal sculpturing; c, shriveled female after oviposition; d, foot of same; e, rudimentary and functionless mouth parts. (Marlatt.) Fig. 118.—Ladybird feeding on scale insects, Pentil’ia (Smilia) misel’la: a, beetle; b, larva; c, pupa; d, blossom end of pear, showing scales with larve and pup of Pentilia feeding on them, and pupz of Pentilia attached within the calyx; all enlarged. (Howard and Marlatt, Bull. U. S. Dept. of Agriculture.) of the same species, says Comstock, differ greatly. The males, unlike all other members of the order, undergo a complete metamorphosis. The adult 148 BRANCH ARTHROPODA male has but a single pair of wings and has no organs for procuring food. The mouth parts disappear during metamorphosis and a second pair of eyes develops. The adult female is always wingless and the body is always seale-like or gall-like in form, or grub-like and clothed with wax. Those of some species retain their eyes, antennz, and legs, while others are fixed in adult life and very degenerate, lacking eyes, antennz, wings, and legs. In speaking of the San José scale, Kellogg says, ‘‘it has a long, fine, flexible process projecting from near the center of its under side, this is its sucking proboscis, and serves as a means of attachment as well as an organ of feed- ing.’ The San José scale is very prolific. It was ascertained at Washington that there are four regularly developed generations and possibly part of a fifth in a year. It is estimated that about 200 females (and about the same number of males) are given birth to by each female. Thus the descendants of a female amount to 3,216,080,400 individuals. From this it can easily be seen how destructive to fruit trees this pest soon becomes. It is now found in every state and territory and in Canada. Many states have laws to try to prevent its distribution with nursery stock. Perhaps the most effective remedy is the fumigation of orchard trees by hydrocyanic gas. To do this the tree is entirely enclosed in a large tent and the gas generated under it ‘ by pouring about 50 ounces of water into 5 ounces of commercial sulphuric acid and dropping into it 15 ounces of cyanid of potassium.” These amounts are sufficient for a tree 12 feet high with a spread of 10 feet. The fumes are deadly poison. Of sprays for leaves and greenhouse plants, crude petroleum and kerosene emulsion are best. Protection of the birds is one great means of holding these pests in check. It has been proved by the examination of 226 stomachs that more than one-fifth of the food of the blackheaded grosbeak (Zamelo’dia melano- ceph’ala') consists of scale insects. For the work (Fig. 118) of ladybird beetles see p. 147. ORDER VIII. COLEOP’TERA This order consists of eleven or twelve thousand species in America, north of Mexico. The mouth parts of beetles (Fig. 119) consist of the upper lip or labrum, the jaws or mandibles for seizing the prey or for gnawing; the complicated many pieced mazille with usually prominent maxillary palpi; the lower lip or labiwm of several parts, and rather large labial palpi. These mouth parts are adapted for biting, and are not easy for beginners to identify. The student should identify these parts on a large beetle with the help of a good figure (Fig. 119) and a good magnifying glass. Compound eyes are present, but usually the simple eyes are wanting. The wings are four in number, except in some ground beetles, which have only the anterior pair. The anterior wings are 1 Plate III, Bulletin 32, U.S. Biological Survey. COLEOPTERA 149 quite rigid and meet in a line on the back, forming a sheath to inclose the membranous posterior wings, which fold up under the fore wings or elytra when not in use. The body is usually compact. The under surface of the abdomen is hard, but the upper surface beneath the elytra is soft and yielding, thus permitting respiration. Fig. 119:—Under surface of Har’palus caligin'osus: a, Ligula; b, para- glossa; c, supports of labial palpi; d, labial palpus; e, mentum; f, inner lobe of maxilla; g, outer lobe of maxilla; h, maxillary palpus; 7, mandible; k, buccal opening; J, gula or throat; m, m, buccal sutures; n, gular suture; 0, prosternum; p’, episternum of prothorax; p, epimeron of prothorax; q, 7, 7’, coxe; 7, r’, r’’, trochanters; s, s’, s’’, femora or thighs; ¢, ¢’, t’’, tibiz; v, v?, v3, ete., ventral abdominal segments; w, episterna of mesothorax (the epimeron is just behind it); x, mesosternum; y, episterna of meta- thorax; y’, epimeron of metathorax; z, metasternum. (After Leconte.) The Young.—The metamorphosis is complete. The larve are usually called grubs. (See Fig. 120, p.150.) Their habitats vary much. Some live in trees, others, as the larve of the tiger beetle, burrow in the gound, and, with the head at the sur- face, watch for their prey. Their food varies according to the 150 BRANCH ARTHROPODA habitat. The burying beetles (Fig. 120) (Nécréph’orus) pro- vide food for their young by burying carrion, as a dead mouse or bird. When it is covered over with earth the female lays her eggs upon the carcass. They soon hatch and the larve feed upon the food thus provided for them. The food of the adult Coleop’tera also varies much. Some, as the ground beetles (Carab’ide), are predaceous. Others, as the carrion beetles, feed upon decaying animal matter, while Fig. 120.— Necroph’orus burying a mouse, and larva. (Landois.) others, as the Colorado potato beetles, are voracious plant feeders, making this order of much economic importance. Other familiar examples are the apple-tree borers, the wire-worms, fruit and grain weevils, and the white grubs of the June beetles (Fig. 121). The tiger beetles (Cicindel’ide) are usually of a beautiful metallic green or bronze, banded or spotted with yellow, though some are black, while those living in white sand are exactly the color of the sand. They are the most active of all beetles, running and flying well. They may be found on bright warm days on dusty roads or along the banks of streams. COLEOPTERA 151 Comstock says they remain still until within our sight, but out of reach, and then “ like a flash they fly up and away, alighting several rods ahead of us,’ with eyes toward us. The ugly larve live in vertical burrows about a foot deep on beaten paths or in the sand. The larva, with its dirt- colored head which is bent at right angles to its lighter colored body, plugs the entrance to its burrow, and with its wide-open jaws forms a living trap for passing insects. On the fifth abdominal segment there is a hump bearing two hooks curved forward, by which the larva holds fast, thus pre- venting large prey from dragging it out of its burrow. The ground beetles (Fig. 122) (Carab’ide) are probably the most im- portant family of predaceous insects, though a few species are vegetable feeders. They are usually dark colored and nocturnal, but some are large and brilliantly colored, and the wing covers are generally ‘‘ ornamented with longitudinal ridges and rows of punctures.” They hide in daytime under stones and logs. There are about twelve hundred species in North Fig. 121.—June beetles: 1, Pupa; 2, larva; 3, 4, adult. (Riley, Report of State Entomologist of Missouri.) America. The larvee of most of them are long flattened erubs, with body of uniform breadth throughout, protected on top by horny plates, ending in a pair of conical bristly appendages. Usually they bury themselves just beneath the surface and feed upon insects which enter the ground to pupate. They destroy large numbers of leaf-feeding beetles or their larve. They pupate in small round cells in the soil, from which the adults push their way out. The caterpillar hunter (Caloso’ma scruta'tor) is a familiar example of the ground beetles (Fig. 122). Its wing covers or elytra are bright green or violet, margined with reddish. It is found on trees at dusk. It is known to climb trees and make raids upon the hairy tent caterpillar, hence it is a friend. Two others (Calosoma frigidum and C. calidum) are hunters of cut- worms and canker-worms. The latter is sometimes called the fiery hunter, from the rows of reddish pits on its black elytra. Another one (Agonod’erus pal'lipes) feeds upon sprouting corn, 152 BRANCH ARTHROPODA The carnivorous water beetles (Dytic’ide), of which there are three hundred species, are found everywhere in streams and ponds (Fig. 123). They vary in length from 4 to 13 inches. The diving beetle projects the tip Fig. 122.—Ground beetle (Calosoma), similar to C. scrutator; below, a Carabus. (Brehm.) of its abdomen through the surface film to breathe. It raises the elytra a little, and the air which is caught under them is held by the fine hairs on the eG Z i 5a Ve Wy) pe Fig. 123.—Carnivorous water beetles. (Brehm.) back, where the spiracles are situated. Thus, it carries a supply of air which enables it to breathe under water. These beetles make interesting aquarium specimens. DIPTERA 153 Platypsyl’la casto’ris is the sole representative of the family Platypsyl’lide. This queerly shaped beetle lives a parasitic life upon beavers. It is wingless and blind, and the elytra are rudimentary and short, exposing five abdomi- nal segments. Its degeneration is due to its parasitic life. The lady-bugs (Coccinel’lide) are interesting little predaceous beetles, yellow or reddish, with black spots. The cottony cushion-scale (Ice’rya purchasi), so destructive to California fruits, was subdued by a lady-bug (Veda'lia cardina’lis) brought from Australia to feed upon it. The hop louse is destroyed by the larve of certain lady-bugs known as “ niggers.” The lady-bugs, with few exceptions, are predaceous. One (Epilach’na borea/lis) is herbivorous. Its larva, which is yellow and clothed with forked spines, feeds upon the leaves of the squash family. _ The little carpet beetle (Anthre’nus scrophula’rie) is a household pest. Its larva feeds upon carpets, furs, feathers, and woolens. The fireflies (Lampyr'ide) or ‘“‘ lightning-bugs ”’ are not flies, but beetles. The light giving has never been fully explained. “ The light-giving organ is usually situated just inside of the ventral wall of the last segments of the abdomen, and consists of a special mass of adipose tissue richly supplied with air-tubes (trachez) and nerves. From a stimulus conveyed by these special nerves oxygen, brought by the network of trachez, is released, to unite with some substance of the adipose tissue, a slow combustion thus taking place. To this the light is due, and the relation of the intensity or the amount of light to the amount of matter used up to produce it is the most nearly perfect known to physicists.” Myrmecoph’ilous Beetles——There are nearly one thousand species of beetles which live in the nests of ants. Many of them are commensal with the ants, deriving perhaps the greater benefit by the association, but others live truly symbiotically with their hosts.2 They secrete a sweet substance which is eaten by the ants, which in return shelter, clean, and, by regurgitation, feed them. They are strangely modified for this mode of life, usually by degeneration. ORDER IX. DIP’TERA This order contains about fifty thousand species, of which about seven thousand are known in America. It includes some famous flies (Fig. 124). The mouth parts are adapted for piercing and sucking or for lapping. Just what constitutes these mouth parts 1s a contro- verted question among scientists. Comstock says, ‘‘ According to the most generally accepted view the six bristles represent the upper lip (labrum), the tongue (hypopharynx), the two mandibles, and the two maxillz, and the sheath enclosing these bristles is the lower lip (labiwm).” Identify these parts on the head of a big fly with the aid of a large figure and a magnifying glass. 1 Kellogg, p. 269. 2 Kellogg, p. 553. 154 BRANCH ARTHROPODA The Wings.—As the ordinal name indicates, these imsects have two membranous wings. No fly has more than two wings and only a few are wingless. They have, however, vestiges of a second pair, called halte’res or balancers, ending in short knobs. They are used in directing the flight and are be- lieved by some to be auditory organs. Family Mus’cide.—The common house-fly (Mus'ca domes’tica) is too well known for our comfort. It hibernates. One will recall having seen flies about the house during the winter. They breed about stables in the sum- : S Fig. 124.—Typhoid fever or house-fly (Mus’ca domes’tica): a, Adult male; b, proboscis and palpus of same; c, terminal joints of antennz; d, head of female; e, puparium; f, anterior spiracle; all enlarged. (Howard and Marlatt, Bull. U. S. Dept. of Agriculture, 1896.) mer. The eggs, numbering about one hundred, hatch in about twenty- four hours. The soft, white, cylindric, footless larva is called a maggot. It feeds and grows for about a week, molting twice, and then pupates within the larval skin, or pupariwm, for another week. It then makes a circular opening in the puparium and emerges as the: adult fly, thus giving time for a number of generations. In a summer the offspring of a single fly may reach incredible numbers. It is now known that the principal in- sect agent in the spread of typhoid fever is the common house-fly, and great care should be taken to prevent its breeding. All human and horse excreta should be kept in fly-tight vaults and sprinkled with chlorid of lime or quick lime at least once a week, unless wanted for fertilizing purposes, All garbage cans and swill pails should be kept covered, and DIPTERA 155 sprinkled with lime when emptied. Chicken pens should be cleaned often and sprinkled with lime. The many little projections on the feet of the fly are tubular, and secrete a sticky fluid which enables it to walk upside down. The blow-fly and the flesh-fly, close relatives of the house-fly, lay their eggs upon meat, cheese, and other provisions or upon decaying animal sub- thorax %. a - -head- Fat cs Zp tarsus id ntennae® Os - ws basal segment o------ ep basal Diand=2-2--¥ basal ena of segment... § apical end of segment. Ba: Ay pa. a 4 s The _ he ebieal segment_., en © tarsus v y* XN 2 i. t = Se ail if _J*Varsal jo nt \ a bose........ atk coe base eee fs. 2 tesecl| jot, : f’ oS Larsal fone a ef Z E tarsal jornticy s Bissccn cee tons sa receoe ctarsal clawg-: NE aera, con st tarsal font Fig. 125.—An adult mosquito, much enlarged, with all the parts that are used in classification named. (Smith, N. J. Experiment Station, Bulletin 171, 1904.) stance, on which the maggots feed. Thus, while a great annoyance, they may do some good by acting as scavengers. The most common flesh-fly is perhaps Sarcoph’aga sarrace'nie, which resembles a large house-fly. id furnishes another example of viviparous insects; in other words, the larve are brought forth alive. 156 BRANCH ARTHROPODA Horse-flies (Taban’ide) are also pests of man and beast. . They are most abundant in the hot summer days. The large black-bodied horse- flies, of which there are a hundred species, belong to the genus Tabanus. The Bot-flies (Ch'stride).—‘‘ The horse bot-fly (Gastroph‘ilus e’qui) closely resembles the honey-bee in form, except that the female has an elongated abdomen curved under the body.” Horses have an instinctive fear of this fly. It attaches its eggs to the hair of the legs and shoulders of the horse, and they are taken into the mouth by biting the irritated place. The larvee fasten themselves to the lining of the stomach. When grown, during the fall and winter, they pass out and develop within a puparium. The larvee of Bot-flies of cattle or oxwarbles (Hypoder’ma linea’ta) live just beneath the skin on the backs of cattle, which are made frantic by their burrowing. The sheep bot-fly deposits its larve in the nostrils of sheep, antelope, ete. They work up into the frontal smmuses and horns and cause the “ staggers.’”! Reindeer, deer, rabbits, and squirrels are infested by larvee of species of bot-flies, and one or two species infest man. Fig. 126.—1, Egg-mass of the common mosquito; 2, larva breathing at the surface of the water; 3, a pupal mosquito. (From Hampton Leaflet.) Mosquitoes (Culic’ide) (Fig. 125) seem too well known to need descrip- tion, but there are other insects so similar that they are often mistaken for them. Comstock says ‘‘ the most distinctive feature of mosquitoes is the fringe of scale-like hair on the margin of the wing and also on all known American forms on each of the wing veins.”” The males differ from the females in having feathery antenne and in the absence of the piercing stylets. As a rule they do not sing or bite, and probably feed upon the juices of plants, as do the females if they cannot ‘‘ get blood.”’ The larve (Fig. 126), called “ wrigglers”” or “ wiggle-tails,” are too often found near our dwellings in rain-barrels, slop-pails, open cisterns, open sewers, water troughs, lily-tubs, ponds, anywhere where the water is allowed to remain long enough for their development, which requires from eight to eighteen days. Of the three principal genera, Culex contains most of our mosquitoes whose bite and song are well known. Anoph’eles is the genus which is the intermediate host and the transmitter of the malaria germ. Of course it cannot transmit 1 Comstock, p. 478; Hertwig, p. 493. DIPTERA 157 these germs unless it has been infected with them itself. Stegom'yia fascia’ta (Fig. 127) is the yellow-fever-carrying species, so much dreaded in our southern states. It has been established by observation and ex- periment! that these mosquitoes, if they have bitten persons affected by malaria or yellow fever, actually carry these diseases, also that Steg- omyia fascia’ta and Culex fati’gans, var. skusii, and Anopheles rossii carry certain forms of filariasis. These organisms belong to the round worms or Nematoda (see p. 41). The most common form of filariasis is elephantiasis. In this disease the legs and arms are af- fected. One leg may become so enlarged as to weigh as much as the rest of the body, or the arm may become a foot thick and horri- bly repulsive. In Samoa, says Kel- logg, fully one-third of the natives are attacked by this incurable dis- ease, which, though slow and almost painless, is certainly fatal. Ma- laria, so widespread in the United larged). of Agriculture, 1902.) Fig. 127.—Stegom'yia fasci'ata (en- (Howard, Bull. U.S. Dept. States, becomes even more prevalent and more often fatal in the tropics. Millions die from it every year. of malaria in India alone. In a single year five million persons died Hence the mosquito is to be classed not sim- ply as a great annoyance, but as an insidious foe to health and life. Fig. 128.—The common harmless mosquito stands this way on a ver- tical or horizontal surface. (From Hampton Leaflet.) Fig. 129.—The malarial mosquito stands with its head pointing down- ward at an angle of from 20 to 30 degrees from a vertical or horizontal surface. (From Hampton Leaflet.) The common mosquito, Culex (Fig. 128), may be distinguished from the malaria-carrying form (Fig. 129) in several ways. The female Culex has 1 Kellogg, pp. 617, 630. 158 BRANCH ARTHROPODA short palpi, while the Anoph’eles has palpi nearly as long as the beak, making three long projections on the head. It may be distinguished also by the way it alights. The Culexis ‘ hump-backed” with the beak pointing down- ward, while in the Anopheles the body and beak he in the same plane. The eggs of Culex are laid in a boat-shaped mass, while the eggs of Anopheles are laid “ singly and at random,” but run together, forming irregular groups or strings. The larva of Culex hangs with the head down, so as to keep the end of the respiratory tube, which is borne by the next to the last somite, in contact with the air. The larval stage lasts about five or six days or longer in unfavorable conditions. The larva of Anopheles has a very short respi- Fig. 130.—A fine breeding-place for mosquitoes. (Hampton Leaflet.) ratory tube, and consequently lies in a horizontal position just under the surface film in order to obtain air. (This explains how it is that kerosene oil ‘poured upon the troubled waters’’ destroys the larve. They are simply drowned or suffocated as the surface film of oil excludes the air.} The larval stage lasts from twelve to fourteen days. The mosquito larva, after growing several days and molting twice, changes into aclub-shaped pupa (Fig. 126), the head and thorax being greatly en- larged, while the abdomen is slender. At the caudal end is a pair of leaf- like locomotor or swimming appendages. It takes no food, and when un- disturbed it floats upon the water, but when disturbed it is active, thus differ- DIPTERA 159 ing from the pupal stage of most insects. The pupa of Anopheles has a narrower and more pointed head and much shorter and wider breathing tubes than those of Culex. Mosquitoes flourish alike in the heated moist regions of the tropics and in the frigid regions of ice and snow. Many species have their haunts and breeding-places in fresh water, others breed abundantly and some perhaps exclusively in brackish water. They are found even in arid regions far from water, where it is probable they lay their eggs in the ground. So, go where we will, we cannot escape them, we must fight them. Fig. 131.—Wheat plant, showing injuries by Hessian fly: a, Egg of Hes- sian fly; 6, larva; c, flaxseed; d, pupa or chrysalis; e, female, natural size; f, female; g, male; h, flaxseed or pupal stage between the leaves and stalk; 1, chalcidid parasite; all enlarged except wheat stem ande. (After Riley, Burgess, and Trouvelot.) A very easy and successful way of getting rid of mosquitoes in a pond which will sustain fish is to stock it with such fish as the ‘‘ top-minnow,” sun-fish, and stickleback, whose young especially feed upon the larve. Dragon-flies also should be encouraged and protected, since their nymphs feed upon the larvz of mosquitoes, and the adults are voracious feeders upon the mosquitoes. In fact, if it were not for the dragon-flies, life in the Hawaian Islands would be almost intolerable on account of the hordes of mosquitoes. Pools and marshes should be drained, or, if the pool or mud- 160 BRANCH ARTHROPODA puddle is small, it may be filled up with less expense. If neither can be done, then spraying with kerosene along the edges of the banks and the surface of the water every two or three weeks should be resorted to. The oil kills by contact many adults and larvae among the grass and weeds, and by coating the surface of the water with a film of oil the “ wiggle-tails ”’ are suffocated. Many females also are killed by this film of oil when they return to the surface to deposit their eggs. All open barrels (Fig. 130) and cisterns should be screened, so that the female mosquito cannot get to the water to deposit her eggs. The gall-gnats (Cecidomyi'ide) are the smallest flies, but their great num- bers and their gall-forming habits make them great enemies of plants. There are about a hundred species in the United States, most of which are “DIPTERA: HYMENOPTERA: Volucella 1NANS. Vespa VULGARIS. Vot«1- Bows YLANs: Bomeus Larivarius. Fig. 132.—Two cases of mimicry: flies resembling a wasp in the one, and a bee in the other. (Romanes.) destructive to cultivated plants. The minute reddish or white eggs are deposited on or in living plants, and the maggot-like larve probably imbibe their food through the skin. The Hessian fly belongs to this family. It is a tiny blackish midge which lays its eggs (Fig. 131) in the sheaths of leaves some distance from the ground. The larva lives between the base of the leaf and the main stalk and feeds upon the sap of the growing wheat. There are four or five broods a year, both spring and winter wheat being infested. It is estimated that the ravages of this insect cost the farmers of this country $10,000,000 annually. Were it not for its natural enemies, a half-dozen hymenop- terous parasites, it would soon take the whole crop of wheat, rye, and barley. The chief remedies which the farmer can use are the late planting SIPHONAPTERA 161 of winter wheat; the burning or plowing of stubble; the early planting of strips of decoy wheat to attract the egg-laying females to deposit their eggs, and then to be burned; and the rotation of crops.! Another common and conspicuous gall-gnat is the pine-cone-willow gall- gnat, which lays its eggs in the newly formed buds of the willow. The stem ceases to grow, but the leaves continue, causing the bud to resemble a pine-cone. In this the larva remains through the summer and winter, pupating in early spring, soon after which the adult emerges. There are a number of others, as the clover-leaf midge, the clover-seed midge, and the wheat midge, each injurious to its respective crop. The Syrphus flies (Syr’phide), of which there are twenty-five hundred species, differ much. Some species in the adult form imitate bees and wasps (Fig. 132). They can be distinguished by the longitudinal ‘“ spu- rious”’ vein between veins three and five. Some of the larve are found in ants’ nests and some in the nests of bumble-bees and wasps. One of the commonest is the yellow-banded species of the genus Syrphus, whose larvee do great good by destroying aphids, in whose colonies they live. The larvz of one of the bee-flies (Bombyli’ide) are also friends of man. They destroy many grasshoppers by burrowing into the egg-cases and devouring the eggs. The adults of these maggot-like larve are swift, hairy, and bee-like, mimicking the bee in appearance and feeding habits. ORDER X. SIPHONAP’TERA The fleas consist of a single family, the Pulic’ide, of nearly one hundred and fifty species, about fifty of which are found in the United States. Until recently the fleas were regarded as degenerate wingless Diptera, but entomologists now place them in a separate order. They are found usually as temporary external parasites on the cat, rat, rabbit, dog, poultry, and man. The mouth parts are adapted for piercing and _ sucking. They are almost wingless, the wings being represented by mere scaly plates. The bodies are naked, smooth, hard, oval, and compressed. The metamorphosis is complete (Fig. 1383). The “small, slender, white, footless, worm-like grubs” are composed of thirteen segments. They seem to live on dry dust and the organic matter it contains. When grown they usually spin a silken cocoon and pupate in the dust. In the species infesting cats and dogs the larval life lasts only about a week. The development from the egg to the adult requires but two weeks. Fresh pyrethrum dusted about the rugs where dogs and cats lie, or spraying the rugs with formalin, will help get rid of fleas. 1 Jackson and Daughterty’s “‘ Agriculture through the Laboratory and School Garden.” 11 162 BRANCH ARTHROPODA The chig’oe, a small flea of the West Indies and of South America, often causes serious trouble by burrowing under the toe-nail or the skin of the foot of man. The female burrows under the skin, becomes encysted and dis- tended by the eggs which hatch here, and unless the young are carried out by the pus they probably develop here. na ae Fig. 133.—Common cat and dog flea (Pii’lex serrdt'iceps): a, Eggs; b, larva in cocoon; c, pupa; d, adult; e, mouth parts of same from side; f, labium of same from below; g, antenna of same; all much enlarged. (How- ard, Bull. U. 8. Dept. of Agriculture, 1896.) Rat Fleas.—It is believed that in tropical countries the disease germs of the bubonic plague may be transmitted from rats to men by the bites or punctures of rat fleas. ORDER XI. LEPIDOP’TERA This order includes such common insects as butterflies and moths or “ millers.”” There are more than 6600 species in North America. The head is rather small for the size of the body. The mouth parts are highly complex, a striking example of adaptation of structure to function. The two maxille are greatly modified into a long hollow tube (Fig. 141) for sucking the juices of fruits or the nectar of flowers. When not in use this tube, tongue, or proboscis is coiled up between two projections, the labial palpi. Many moths do not feed in the adult stage and the maxille are lacking. The other mouth parts are mere LEPIDOPTERA 163 rudiments. Find these rudiments on a large specimen and compare with the mouth parts of the grasshopper. The compound eyes are large and conspicuous. Some of the Lepidoptera have ocelli,t one on either side above and near the margin of these compound eyes, but they are usually hidden by the scales covering the head. The many jointed antenne are very various in size, shape, and color. _ The thoraz bears three pairs of legs and two pairs of wings. The wings are large, membranous, and covered with overlapping scales, which are, in reality, modified hairs. These scales strengthen the wings and give coloration to the species. The abdomen has no paired appendages. The metamorphosis is complete. The larve of Lepidoptera are commonly called caterpillars. They are very destructive, being almost without exception injurious to vegetation. Com- stock says, ‘“‘a very few feed upon plants below the surface of the water.” The species which destroys scale-bugs, also those attacking woolen cloth, feed upon animal matter. Caterpillars are usually cylindric. The thorax bears six clawed, jointed, tapering legs, which develop into the legs of the adult. The ab- domen bears from two to ten thick, fleshy, non-jointed, contrac- tile pro-legs (see figure of silkworm, p. 126), which are shed at the last molt. The pro-legs are usually surrounded at the ex- tremity by many minute hooks. The mouth parts of caterpil- lars are formed for biting, hence they can be exterminated by the arsenical poisons when it is safe to use them. The Lepidoptera pupate in chrysalids or cocoons. The adult stage is the familiar winged form. It does no harm except the occasional puncturing of fruit to get the juice. Distinctions Between Butterflies and Moths.—The antenne ot butterflies are filiform or thread-like for most of their length, but the end is thickened into a spindle-shaped enlargement or club. The antenne of moths are of various forms, usually filiform or pectinate (feathery), but never clubbed. Butterflies are diurnal, while the moths are crepuscular or nocturnal. Butterflies at rest fold the wings together in a vertical position above the back. Moths spread the wings horizontally, or fold them leaf- 1Comstock, p. 199. 164 BRANCH ARTHROPODA like, or wrap them about the body, but never hold them in a vertical position. The skipper butterflies are diurnal, but, unlike other butter- flies, the antennze are usually recurved, forming hooks. Their bodies are more robust than those of other butterflies. They fold the wings, sometimes only the front ones, vertically when at rest. The skipper caterpillars are distinguished from other caterpillars by the unusually large head and the much constricted neck. Skippers spin thin cocoons of silk in which to pupate. Authorities enumerate 650 species of butterflies in the United States east of the Mississippi River. Kellogg gives six families of butterflies and forty-four of moths. Of the thousands of species with their various and interesting habits only a few can be mentioned. These should serve to stimulate the student to observe and study others. See “ Laboratory and Field Guide” for collecting, breeding, and mounting. The carpenter moths (Cés'sid@), of which there are twenty species in North America, are, in the larval stage, wood-borers, burrowing about in the heart- wood of shade and fruit trees. Pepper and salt gray moths, indistinctly or, in a few cases, conspicuously marked with black and white, lay their eggs on the bark of trees, where the naked, grub-like larvae burrow into the wood. Here they tunnel through the wood for two to four years, according to the species. In this tunnel the pupal stage is spent. When ready for the adult stage the pupa works its way, by backward projecting saw-like teeth on the abdomen, to the opening of the tunnel, from which the moth emerges. The empty pupa skins may often be found projecting from the deserted burrows. The meal moth (Pyr’alis farina'lis), whose larva feeds upon meal, flour, or old clover-hay, is a common species. It is usually found near the larva’ food, but sometimes sits upon the ceiling with its tail curved over its back. Its expanse of wing is about an inch. The wings are light brown with red- dish reflections and a few wavy transverse lines. The larva makes long tubes of silk in the meal. Perhaps the most formidable mill pest is the Mediterranean flour moth (Hphés'tia kuehniél'la). The caterpillars spin | silken galleries through which they pass, making the flour lumpy and stringy. The coccid-eating pyralid (Letil’ia coccidiv'ora) differs from other members of its family in being predaceous. It feeds upon the eggs and young of several scale insects. The larva spins a silken tube or bag, in which it lives. The codling moth (Carpocap’sa pomonel’la) (Fig. 134) is one of the best- known and most cordially hated of moths. It causes an annual loss in the United States of $10,000,000. The adult is small, with finely mottled, ash- gray or rosy fore wings. Near the square ends of these wings is a large brown- ish spot marked with metallic, bronze bands. The hind wings and abdomen are a lustrous light yellowish brown. This moth lays its eggs singly in the blossom end of an apple, just when the petals fall. When the larva hatches LEPIDOPTERA 165 it eats its way into the core. The affected fruit usually falls to the ground before ripening. The full-grown larva burrows out of the apple and pupates in a cocoon under the rough bark of a tree. After two weeks in the pupal stage the adult of the first brood emerges and lays its eggs on later apples. The larve are carried into the cellar with the fall and winter ap- ples, pupate in the crevices of the barrels or boxes, and remain till the fol- lowing apple-blossom time. Spraying the fruit with Paris green soon after the petals fall and again in about two weeks will greatly reduce the loss. At this time the fruit stands with the blossom end up and the poison will then reach the place where the larva hatches.”! The larva does not remain long in the apple after it falls to the ground. Hence if the apples are burned or fed to hogs at once the larvze will be destroyed. Pe | 5 Fig. 134—The codling moth: a, Apple showing burrow; 6, place where the worm entered; d, chrysalis or pupa; e, larva or worm; f, moth with wings closed; g, moth with wings spread; h, head end of larva; 7, cocoon in which the larva changes to a chrysalis. All about life size except h. (Riley.) The geometrids are of interest because of the peculiar phase of protec- tive resemblance possessed by their larvee. They cling by their posterior legs to the branches of trees or other plants, and, holding the body out straight, stiff, and still, look, for all the world, like short, stubby branches. My little daughter searched for fully five minutes within a few inches of a green specimen on a sweet-pea vine before discovering it. When disturbed the caterpillar swings down by a silken cord till it reaches the ground. Most of them are leaf eating and they are sometimes so numerous as to do great injury. Among them are the canker-worms (Fig. 135), currant span- worms, two or three species which feed upon the grape, and the raspberry geometrid. They may be poisoned by Paris green, since all insects with biting mouth parts can be killed by poisoning the food with arsenical sprays. 1 Jackson and Daugherty’s ‘“‘ Agriculture,” p. 321. IGG BRANCH ARTHROPODA The owlet moths ( Noctw’ide@), of which there are more than twenty-five hundred species in America, fly at night and are familiar visitors around our Fig. 185.—The spring canker-worm: a, Egg mass, natural size; b, egg, mag- nified; c, larva; d, female moth; e, male moth. (Riley.) evening lights. To these belong the numerous cut-worm moths and army moths. Most of this large family are inconscipuous and dull colored, but Fig. 136.—The boll-worm or corn-ear-worm. (Riley.) the group of “ underwings,” or Catoc’alas, are exceptions to this rule. Strangely enough it is their posterior or under wings which are conspicu- ae ae ee LEPIDOPTERA 167 ously colored and banded. When at rest the inconspicuously marked dull-colored fore wings completely cover the hind wings. During the day the moths rest close against the bark of tree trunks, where it is almost im- possible to distinguish them. Collectors smear syrup on the trunks of trees where no sweet-smelling flowers are near, and collect the insects thus ues on a dark, damp night, with a dark-lantern and wide-mouthed ottles. The cotton worm (Alé’tia argilla’cea) also belongs to this family. It feeds upon the leaves of the cotton plants. The cotton boll-worm ( Helio’- this armig'era) (Fig. 136) feeds upon the pods or bolls. The destruction caused by these two caterpillars causes an annual loss of millions of dollars Wil (( i) Fig. 137—Corn-worm eating an ear of corn. (Quaintance, F. B. 191, 1B Idi, We Sy IDL Ny) to the cotton growers. The boll-worm has become a great pest in the north also as the corn-ear-worm (Fig. 137). Just at the roasting ear stage it eats the juicy kernels and leaves a disgusting dark furrow, unfitting the corn for use. It feeds upon the fruit of the tomato also. The naked, greenish-brown caterpillar is marked longitudinally with darker stripes when grown and is about 11 inches long. It pupates in the ground through the winter. The moth has dull yellowish fore wings tinged with green. The hind wings are paler. Since it works under cover of the husk, spray- ing is of no use. Fall plowing practised by all neighbors having infested corn will materially lessen the number of worms. As the moths fly well, it would do comparatively little good for one to plow unless the near neigh- bors unite in the effort. Rotation of crops is helpful, 168 BRANCH ARTHROPODA The tussock moths (Lymantri’ide) (Fig. 138) are of medium size, the antenne of the males being more broadly pectinated than those of the females. Ocelli are lacking. In some species the females are wingless. The legs are woolly or hairy. The larve are more beautiful than the adults. They have several bright colored tufts of hair on the back and long pencils Fig. 138.—Orgyia leucostig’ma: a, Larva; b, female pupa; c, male pupa; d, e, male moth; f, female moth; g, same ovipositing; h, egg-mass; 7, male cocoons; k, female cocoons with moths carrying eggs. All slghtly en- larged. (Howard, Farmers’ Bull., U. 8S. Dept. of Agriculture, 1899.) of hair on each end of the body. The sixth and seventh segment each bears on the back a coral-red scent gland. It is easy to guess whether these caterpillars are a favorite food of birds. They infest our shade and orchard trees. The eggs are usually deposited upon the cocoon from which the adult female has just emerged, so they may be destroyed by collecting and burn- ing the cocoons in winter. LEPIDOPTERA Fig. 139.—A, Male, and B, female, gypsy moths. Natural size. (Forbush and Fernald.) wh LE as ev Sy M ig THE EGGS REMAIN ON THE TREES ‘ sf =) NINE MONTHSIN THE YEAR;FHEMOST 2 \ Es|. VITAL PE RIOD; INTHE LIOR 2. \e| = ; THE ee LIFE\MOTH & | ‘CYCL = EASE Fig. 140.—The lifé cycle of the gypsy moth. (Figures after Forbush and Fernald.) (Bull. No. 121, New Hampshire State Experiment Sta- tion, December, 1905.) The gypsy moth (Ocne’ria di'spar) (Fig. 139), imported from Europe ‘in 1868, has become a great pest of forest and shade trees in Massachusetts. 170 BRANCH ARTHROPODA The state fought it in every possible way, employing hundreds of men in spraying, trunk-banding, and egg-collecting. From 1890 to 1900 Massa- chusetts spent more than a million dollars in keeping this moth in check. The hawk moths (Sphin'gide), sphynx moths (Fig. 141), or humming- bird moths have a stout, spindle-shaped body and long, narrow, exceed- ingly strong wings. The sucking tube is very long, sometimes twice as long as the body. When not in use, it is coiled up beneath the head like a watch-spring. Their rich varied tints of olive, tan, black, or yellow, always subdued, save for an occasional dash of bright color on the under parts, mark them as rarely beautiful creatures. As a rule, these moths love the Fig. 141.—Tomato-worm or tobacco-worm: larva, pupa, and adult. (After Walsh and Riley, Am. Ent.) twilight, and strangely resemble the humming-birds from their habit of rap- idly vibrating their wings while poising themselves over a flower and suck- ing its nectar. The larva, naked and cylindric, usually has a ‘“ horn ”’ on the back of the eighth abdominal segment. These caterpillars are usually green with several oblique light-colored or whitish lines on each side (see Fig. 141). When resting these caterpillars “‘ rear the front of the body up in the air, curl the head down in a most majestic manner, and remain thus rigidly motionless for hours.”! They are thus supposed to resemble the Egyptian sphynx, hence the name, sphynx moth. They feed upon the leaves of 1 Kellogg, 331, LEPIDOPTERA 7 various trees or plants, the tomato-worm being perhaps the most familiar example. When full grown this is sometimes 3 inches long. The pupa, which lies buried in the ground, has a firm, naked, dark brown wall, and is distinguished by. the peculiar ‘ jug-handle ”’ sheath, in which the sucking tube is developed. Hand picking of the larvee, fall plowing, and rotation of crops are the’ best remedies. \) Fig. 142.—Metamorphosis of monarch butterfly (Anosia plexippus): a, Egg; b, larva; c, pupa; d, imago or adult. (From Jordan and Kellogg, ‘““ Animal Life,” D. Appleton and Co., Publishers.) The monarch or milkweed butterfly (Ano’sia plexip’pus) (Fig. 142) is one of our most abundant species. Hundreds or even thousands of these butterflies may sometimes be seen in a swarm, or “ roosting’’ together in trees. Their wings are reddish brown, bordered with black, and the veins are edged with black. There are two rows of white spots on the outer margins. iL . BRANCH ARTHROPODA The larva when grown is a very light green or greenish yellow, and regularly marked with shiny black and yellow bands. On the second thoracic and the eighth abdominal segment there is a pair of slender, fleshy, black filaments. This caterpillar feeds upon the leaves of the milkweed. It attains its growth in two or three weeks, when it pupates from nine to fifteen days in a smooth, bright green chrysalis (Fig. 142), which is about an inch long and beautifully adorned with a few black and gilt spots and bands. In the South there are two generations, but with us but one. The butterfly is protected from its enemies, the birds, by an ill-tasting acrid fluid, of which its conspicuous color gives warning. The power of flight is strong and these butterflies migrate in winter. The monarch is found all over North and South America and in most of the Pacific islands, and in Australia and Western Europe. It is closely mimicked by the viceroy (see Fig. 92, p. 119), a smaller butterfly which is not distasteful, but is protected from the birds by its resemblance to the odious monarch. The viceroy may be easily dis- tinguished by the transverse band of black on each of the hind wings. Its larvee feed upon the willow, poplar, and cottonwood. The larva hiber- nates in a silk-lined nest made of a rolled leaf. . The swallow-tailed butterflies (Papilion’ide) are a large and interesting family, having a sort of half-fluttermg, half-soaring: flight. They are easily distinguished by their large size and their black and yellow—or greenish-white—tiger-like markings. Twenty-one species are found in the United States. The wings are very thickly covered with scales. They are narrow and the posterior wings end in a club-shaped prolongation which is supposed to call the attention of the bird to the less vital part. The larvee when disturbed project a pair of bright colored fleshy “horns” from a slit in the dorsal wall of the prothorax. The horns exhale an odor which in some species is exceedingly disargeeable.! The zebra swallow-tail (/ phicli’des a’jax) differs from all other butterflies of the eastern United States by the black and greenish-white bands on its wings and by its exceedingly long “ tails.’”” This butterfly is extremely interesting to the scientist, in that 1t furnishes an example of dimorphism or even of polymorphism. All the broods which hatch out the same summer, and there may be several, are of the same form (ajax), but many individuals pass the winter in the chrysalis stage, some (marcellus) emerging early in the spring, and some (telamonides) appearing in late spring. The marcellus form has “ tails”’ only about 2 inch long tipped with white, while the telamonides is a little larger, with tails nearly an inch in length and bordered on each side of their distal half with white; while ajaz, the typ- ical form, is still larger and has longer “ tails.”’ The time of emerging seems to be the only influence controlling this variation, since the offspring of each form, when maturing the same season, produces ajax, when maturing early the following spring, produces marcel- lus, and late the following spring, telamonides. The larva of this species is light green, ‘‘ thickest in the thorax,”’ and with transverse markings of black dots and lines and slender yellow stripes, be- sides a yellow-edged, broad, black, velvety stripe on the thorax. It feeds upon the papaw. The tiger swallow-tail (Papil’io tur’nus), another common species, is also dimorphic. In this instance the dimorphism is sexual; at least one of the forms, glaucus, is represented only by the female. 1 Comstock, ». 376. LEPIDOPTERA is The cabbage butterflies (Pi’eris) (Fig. 143), of which there are three species in the different sections of the United States, are the most de- structive to agricultural products of any of our butterflies. They have three broods in the North and more in the South. The wings of Pieris rape are a dirty white above, tinged with yellowish in the female. The base and apex of the fore wings are blackish and the female has two black dots on the fore wings; the male has but one. There is a black spot on the anterior margin of the hind wing. In the male it is indistinct. The larva is green, with a narrow greenish-yellow band upon the back and a similar narrow broken “ stigmatal band.” It is covered with fine short hairs. It feeds upon cabbage and other cruciferous plants. It is exceedingly hard to combat, from the facts that there are so many ; ‘da Fig. 143.—Cabbage-worm, and butterfly (Pontia ra’pe): a, Female; b, egg; c, worm eating on a cabbage leaf; d, suspended chrysalis; a, c, and d slightly enlarged. (Chittenden, Cir. 60, B. Ent., U.S. D. A.) broods and that the larva bores into the heart of the cabbage. The work of extermination must necessarily be done before the cabbage begins to head. Fresh pyrethrum and kerosene emulsion are helpful. It is hardly safe to use Paris green except with quite young plants. The gossamer winged butterflies (Lyceni'de) include three well-marked groups which are commonly distinguished by their various colors as the “blues,” “the coppers,’”’ and the “ hair-streaks.’”’ They are quite small and delicate. The larve are slug-like. The ‘‘blues” are often seen flitting about mud-puddles. Several species of the family are carnivorous. One of them, the “ harvester ” (Fenis’eca tarquin’ius), common east of the Mississippi River, is small, with the ‘‘upper surface of wings dark brown, with a large irregular yellow patch on the disk of the fore wing and one of 174 BRANCH ARTHROPODA the same color next the anal angle of the hind wing.” It is a friend to the fruit grower, for its larva feeds upon woolly plant-lice like the apple-tree aphis and the alder blight. ORDER XII. HYMENOP’TERA This order is represented by such familiar insects as the bumble-bees, yellow-jackets, honey-bees, ants, wasps, ichneu- mon flies, saw-flies, and gall-flies. The mouth parts (Fig. 144) are adapted for biting or sucking, the mandibles are short and fitted for biting, while the other Three ocelli or simple eyes \— Compound eyes \- Antenne : Clypeus (c). Mandibles Labrum Palpifer or palpus bearer Maxillary palpi Maxille Paraglosse or lateral lobes of the tongue Labial palpi Lingula or tongue attached at the base of the labium Fig. 144.Front view of the head of a bee. (Tenney.) mouth parts, as the mazille, labium, the maxillary and labial palpi, are more or less modified into a proboscis for taking up liquid food. The wings are membranous and four in number. The anterior pair is larger than the posterior. The student will observe that the body and wings of Hymenoptera are shorter than those of the dragon-fly order (Odonata). The metamorphosis is complete. The larve are maggot-like. Habits.—They vary much in habits. Some are herbivorous (saw-flies), some form galls, others are parasitic (ichneumon HYMENOPTERA 1a) flies). The stinging Hymenoptera, on account of their efficient means of defense, are often mimicked (Fig. 132, p. 160)—the bumble-bees by the hawk-moths, the hornets by two clear- winged moths of the genus Sesza, the bee by the drone-fly (Eristalis), the wasp by a common English beetle (Clytus erictus), and the hornet by a Nicaraguan Hemiptera. Saw-flies and ‘‘Horntails.’—Among the boring Hymenoptera are the saw-flies, horntails, and gall-flies. The saw-flies have a wide head and thorax, with a broad joining of the base of the abdomen and thorax. The ovipositor consists of a pair of saws with which slits are made in leaves or stems where the eggs are laid. The larvee look much like caterpillars, but may be distinguished by having from twelve to sixteen pro-legs instead of ten. Most of these larve have “a curious habit of curling the hind end of the body sidewise ” about a branch. The rose-slug and currant-worm are familiar examples. The currant-worm is the larva of the saw-fly (Nem/atus ribe’sti). It-1s a ‘‘criminal emigrant’”’ and has left a large army of descendants. The female deposits her glossy white eggs along the ribs of the first leaves of currant and gooseberry bushes. In ten days the little whitish larve hatch. They are voracious feeders and will strip a bush of every leaf if allowed to mature. When mature they are green with a black head and black spots and resemble caterpillars. They pupate in brownish paper-like cocoons, either attached to the bush or hidden in the ground. There are two broods in a season, provided the first is not exterminated by a liberal Fig. 145.—Boring saw-fly or horn- . spraying with Paris green or hellebore. tail (Tré’mex coltim'ba). If the spraying is thoroughly done when the worms are quite small, they are easily poisoned, since, like all insects with biting mouth parts, they swallow the poison with their food. If any of the larvee escape, the spraying must be repeated for the second brood, or the bushes may be killed outright in one season. If the spraying : done soon after the first brood hatches there is no danger of poisoning the ruit. The horntails (Siric’ide@) are so named because the posterior end of the abdomen bears a spine or “horn.”’ They differ from the saw-flies in hav- ing an ovipositor ‘“‘ which is composed of five long, slender pieces,”’ adapted for boring instead of for sawing. There are several species in America. The pigeon horntail (Tr2’mex coltim'ba) (Fig. 145) has a cylindric body about + inch in diameter. It is 14 inches long, with rusty red thorax and black abdomen, with yellow bands and spots on the sides, a yellow “‘ horn- tail,” and smoky transparent wings. The female pierces holes about 4 inch deep in elm, oak, sycamore, or maple trees, bending the ovipositor at right 176 BRANCH ARTHROPODA angles to the body in boring, and deposits her eggs, one in each hole. When the larve hatch they do much injury by burrowing into the heart- wood, where they feed, grow, and finally form cocoons of silk and fine bits of wood. The winged adult gnaws its way out through the bark. The ichneumon fly Thalessa is parasitic upon T'remex. The gall-flies (Cynip’ide) live in closed galls during the larval state, and the full-grown larva either makes a hole and emerges and pupates in the ground, or it pupates in the gall and the adult makes a hole through which it emerges. The adult female pierces a hole in the tissue of the leaf with her sharp-pointed ovipositor which is composed of “‘ several needle-like or awl-like pieces.” In the incision thus made she deposits one or more eggs. When the larva hatches an abnormal growth of tissue begins to form about it, cdused, perhaps, from some irritating excretions, or from the physical irritation caused by the pressure of the irritating body. The tiny, footless, white, maggot-like larva feeds, probably through the skin, on the sap of the growing gall. When the gall dies, which is usually about the time the !arva 1s grown, it dries and hardens and forms a protecting case in which the larva (or larvae) pupates, and from which it emerges as a tiny gall-fly in the first or second spring following. But one of the strange things about these gall-flies is that, in some cases, the successive generations of the same species are not of the same form. The adult flies of one generation, which consists exclusively of females, lay their eggs upon a certain host-plant, but the resulting individuals are not at all like their mothers. This generation includes individuals of both sexes which have developed from ‘ unfertilized eggs,”’ or parthenogenetic- ally. The females of this generation lay their eggs upon a different host- plant, develop very differently shaped galls from those in which they grew up, but, like those of their grandparents, and the resulting individuals are like their own grandparents. Not all gall-flies show this alternation of generation, some species appear always in the same form, but, strange to say, they are usually represented only by females. Although there are two hundred species of gall-flies, each species infests a special part, leaf, branch, or root of one or more particular species of plants. The gall pro- duced by each species of insect is of a definite form. This is a remarkable manifestation of instinct. ‘‘ It is impossible that intelligence or memory can be of any use in guiding the Cynipide@; no Cynips ever sees its young, none ever pricks buds a second season, or lives to know the results that fol- low the act. Natural selection alone has preserved an impulse which is released by seasonally recurring feelings, sights, or smells and by the simul- taneous ripening of the eggs within the fly. These set the whole physiologic apparatus in motion and secure the insertion of eggs at the right time and in the right place.’ The Guest Gall-flies (In’quilines)—There are many gall-flies which do not themselves form galls, but which lay their eggs in the galls formed by others. The larve feed and develop here, but do not materially disturb the rightful owners. Parasitic hymenoptera (Ichneuwmon’ide) are of great economic interest (Fig. 146). Most of them live within the bodies of their victims during the larval stage, the egg being laid either within or upon the body of the host. In the latter case the larva bores its way into the body and feeds upon the blood, so that the host is not killed until the larva is grown. Hach species 1 Stratton. HYMENOPTERA iar of ichneumon flies has its special host, the majority of them being cater- pillars. The largest insect of this family belongs to genus Thalessa. Thales’sa luna’tor has a body 24 inches long and the insect measures nearly 10 inches from the tips of the antennz to the end of the ovipositor, and is parasitic upon the larva of T’remex columba. The ichneumon fly bores a hole with its flexible ovipositor, which is 6 inches long, into the tree infested by Tremex, and deposits its eggs in the burrow of the Tremez larva. ‘When the ichneumon larva hatches, it creeps along the burrow until it reaches its victim, the horntail larva, to which it attaches itself and feeds upon its juices. Sometimes the female ichneumon fly gets her ovipositor fast in the wood and it holds her a prisoner until death. Other important, though usually smali, parasitic Hymenoptera are the braconids, the ensign-flies, and the chaleid-flies. While the larve of para- sitic Hymenoptera are degenerate in the same way as the footless, eyeless, an- tenneless maggots of house-flies, they _ are not more so. Their parasitic habit has led to no such extraordinary struc- tural specialization through degenera- tive loss, or reduction of -parts as is the usual condition in other parasites. The adult is active and well developed. The Stinging Hymenoptera.—The fe- Fig. 146—Pimpla in the act males and sterile workers, where there of ovipositing on cocoon of tent are such, have the ovipositor developed caterpillar. Somewhat enlarged. into an organ of defense, the sting. (After Fiske.) Females may be distinguished from the males by having six segments in the abdomen instead’ of seven. The group includes ants, wasps, and bees. Ants live in all lands and in very various conditions and occupations. All of the 2500 or more species live in communities, and division of labor among kinds of individuals and, consequently, differentiation of structure, are highly developed. Ants are easily recognized by the form of the body, but they are distinguished from other insects by the character of the first one or two segments of the abdomen. These are expanded dorsally into a “ Jens-shaped scale or knot,”’ which varies in form and serves as a peduncle to the rest of the abdomen. The ants’ nests or formicaries are composed of irregular rooms and gal- leries which may be mostly underground, or have a large portion above ground, as a mound or ant-hill, or may be tunnelled out in the wood of de- cayed trees. “‘ In the tropics,” says Comstock, “a greater variety of these structures occur than in our country. . . . One colony of one species has been known to have two hundred mounds covering several hundred square yards. Ants are also very good road makers, sometimes making clean beaten paths or working out covered ways under rubbish.” There are always three classes of ants (Fig. 147) in a community, winged males and females, and wingless workers, sometimes also the soldiers and wingless, but fertile males and females. The winged males and females at 12 178 BRANCH ARTHROPODA maturity issue simultaneously from the nest and from neighboring nests, so that the air will be filled with thousands of ants swarming about in their mating flight. After this the males soon die, and the females which escape from birds and other animals tear off their wings and go in search of a suit- able nesting place. Sometimes the queen starts the new colony alone, while in other species the workers find and adopt a queen and form a new colony. Inside the nest large numbers of very small eggs are laid in “ little piles heaped together in various rooms and sometimes moved about by the workers.”! The larvze are small, white, footless, helpless grubs, which are fed by the workers with regurgitated food or with chewed insects, or with dry seeds and vegetable matter from the granary where they have been stored. Most species spin cocoons in which to pupate—the white oval bodies seen carried away by the ants when the nest is disturbed. The adults Fig. 147.—The pavement ant (Tetramorium cespitum): a, Winged female; b, same without wings; c, male; d, worker; e, larva of female; f, head of same; g, pupa of same; all enlarged. (Marlatt, Bull. U.S. Dept. of Agriculture.) are unable to escape from these cocoons unaided by the workers. The workers are undeveloped females or females which seldom lay eggs, and if they do, these eggs always develop into males. These workers not only feed the colony, but do all the work, building the nests and defending them against enemies, even by war if necessary. There may be from one to thirty queens, though in small colonies there is usually but one. As these queens grow old, the workers seek young queens at the swarming period and bring them into the nest. Ants, except the males, which are short lived, are known to live longer than most social insects. Lubbock says he was able to recognize worker ants at least seven years old, and one queen died when over thirteen years old and another lived more than fourteen years.” 1 Comstock. 2 Lubbock, ‘‘Senses, Instincts, and Intelligence of Ants,” p. 233. HYMENOPTERA 179 Although ants are general feeders upon animal substances and fruit juices, they are very fond of sweet substances like the “ honey-dew” given off by aphids when stroked by the ants’ antennez. In return for this choice food the ants shelter the aphid eggs in their nests through the winter and carry the young plant-lice to tender plants in the spring. When for any cause these plants become unsafe or unfit for the food of the aphids, the ants will carry them to other plants. If ants are seen running up and down the stem of some favorite plant, one may know, unless there is a sweet substance exuding from bark or flower, that they are “ pasturing their cows ”’ upon the juices of tender shoots and newly forming buds. A little close looking will reveal myriads of tiny plant-lice on the under side or in the axles of the leaves. Spraying with a little dilute commercial nicotin -will rid the plants of both ants and plant-lice. Arsenic poisons cannot affect aphids or other insects having sucking mouth parts, since their food consists of the internal juices of plants which cannot be reached by the poison. There are many other insects which live in the nests of anis. In 1900 Wasmann recorded 1177 insects living in the nests of ants (myrmecoph- ilous insects), many of which were beetles. Most of these insects live a commensal life with the ants. It is not known of what advantage they are to their hosts. The guests, however, obtain shelter, food, moderate temperature, defense against enemies, and even, in the case of migratory ants, transportation. In the case of some small beetles, however, there is true symbiosis with the ants, the beetles secreting a sweet substance which the ants eat greedily, and in return the ants “clean, care for, and feed by regurgitation” the degenerate little beetles. The ants furnish an example of a perfect communistic society. There is no special care or favoritism for wife or child or friend, but a common love for the whole community. ‘Everything is done for the good of the whole and nothing for the individual. The state makes wars, provides food for all, cares for the children, owns all the property, the fate of each one is determined by the accident of birth, and each takes up its work without a murmur. . . . This perfect commune has developed courage, patriotism, loyalty, and never-failing industry, but also war, pillage, slavery, and an utter disregard of the rights of other communities and individuals.”* Most of the ants which have been described in this country can be placed in one of three families: (1) Formic’idz, in which is found the interesting carpenter ant (Campon'otus pennsylva’nicus), one of the largest of our com- mon black ants. It builds its nest in the dead interior wood of living trees and wooden buildings. Here also is the mound-building ant (For’mica ex- sectoi'des), with its rust-red head and thorax and black abdomen and legs. Its ant-hills are from 5 to 10 feet in diameter. One of the most interest- ing of the family is the slave-making ant (For’mica diffic’ilis). In this species the workers work with the slaves, but Polyer’gus rufes’cens, a European species, depends upon the slaves to do all the work for the community. The adults are not taken captive, but in war and pillaging the larve and pupz are some of them eaten and some of them carried home, where, if not eaten, they develop into the adult workers, and instinctively go to work for their hosts, building nests, bringing food, and nursing the young. In some species this is carried on to such an extent that the hosts become unfitted for any work but that of warfare, and are dependent solely upon the slaves for shelter, food, and all the necessary work of the community. Thus their 1 Comstock, p. 634. 180 BRANCH ARTHROPODA slave making has reacted upon themselves, rendering them unable to help themselves. It is a law in all animal life that dependence upon others renders one more dependent, while dependence upon self develops inde- pendent powers. The corn-louse ant (Las’ius brun'neus) is the common small brown ant of our pastures, woods, and meadows. It is of especial economic interest on account of the care it bestows on the corn-root plant-louse. The eggs of the plant-louse are laid in the ant’s nest, where they are sheltered during the winter. In the spring the ants place the young aphids upon the roots of certain knot-weeds until the corn has germinated and then remove them to the corn-roots. These aphids do great damage in the Middle West. (See p. 144.) (2) Poner’idz is the smallest family in number of species, there being but about twenty-five known in this country, and the least specialized, that is, the least differentiated into castes. The queen and workers are stingers. Their nests are made under stones or logs. (3) Myrmic’ide.—This family is characterized by two segments in the peduncle. Usually the queen and workers have stings. The pupz are naked. ‘To this family belongs the tiny ‘red ant’ (Monomo’rium phar ao’- nis), which is in reality a light yellow, that is the torment of housewives. The agricultural ants (Pogonomyrmezx) live in the southern and western states. They, with the exception of one species, live in nests partly under ground, covered with conspicuous mounds in open sunny places. They cut away the grass immediately about the nest. It has been popularly believed that they sow the seed for their food, but Wheeler says that they carry out the débris, which consists of chaff and sprouting grain, and deposit it at the edge of the cleared circle. The seeds often grow and do yield a harvest for their next winter’s stores, though not intentionally planted. Intelligence.—There is a great diversity of opinion among scientists who have experimented with ants as to the ‘“‘ mental- ity ” of these insects. Bethe! and others hold to a purely me- chanical or reflex theory, while Loeb, Wheeler, and others at- tribute to them reflexes, instincts, and animal memory, and Lubbock and Forel give them a considerable degree of intelli- gence. Comstock says they “think.” Whether they are governed by one or all of these attributes, it is surely probably that the mechanical and chemical forces which affect the nervous activities of the ants may also influence those of men, and that if the same rigid experiments and final analyses were applied to the various phases of man’s activities, there would result quite as many surprises as have accompanied the experi- menting upon insects, indicating that many of his activities are responses to mechanical stimuli, and yet no one doubts that man possesses intelligence. Whether the activities of ants 1 Kellogg, 544. 2 Comstock, 637. HYMENOPTERA 181 are governed by reflex action, instincts, or intelligence (in a limited degree, of course), or, what is more probable, by a cer- tain combination of these, they certainly perform many won- derful feats, considering the fact that they have but a single set of tools, the mandibles. They use these to dig and tunnel, to obtain food, and to carry and manipulate their food, to fight, to carry tenderly their eggs and young, or tocut leaves and husks and seeds. Though they have no voice, they are known to communicate by means of touch through the agency of the antennz. It is believed that they recognize friend or foe by the odor. The digger wasps (Spheci’na) are a group of closely allied families of Hymenoptera. They may be distinguished from true wasps by the fact that their wings lie flat above the body, and from bees by the adaptation of their legs for digging and walking. They are all solitary. Each female makes her own nest by burrowing in the ground or in wood, or by construct- ing a tube of mud, or using one found already made. In this nest she places certain insects which she has paralyzed but not killed, by stinging, lays an egg, and seals up the cavity. When the larva hatches it feeds upon the food thus provided for it by the mother. The parasitic forms lay the eggs upon the paralyzed bodies of their hosts, and the guest-species lay them in the nests of other wasps or bees, where the larvee feed upon the food prepared by the host for its young. Familiar examples of the digger wasps are the mud daubers (Pelope’us) of our attics and eaves. It is thought that these wasps find their nests again, after going in search of insects with which to “provision” their nests, by the memory and recognition of localities, for they go from place to place, back and forth in many curious zigzag or circular routes, but find their way back to their nests readily. The ‘‘tarantula-killer” (Pép’sis formd’sa), of the West and Southwest, is a large solitary wasp which provisions its nest with the choicest of food, such as tarantulas, though many a hard battle is necessary to procure them. Sometimes the tarantula makes a meal of the wasp instead of becoming food for its young. The true wasps (Vespi’na) are characterized by the folding of their wings lengthwise like a fan when at rest, by the kidney-shaped eyes, and by the absence of bristles or spines from the legs. One family (Humen'ide) of the true wasps leads a solitary life. One of these (Mono'bia quad’ridens) tunnels into wood and partitions off the tunnel, making a cell for each larva. Another species (EHu’menes frater’nus) is a thorough mason, making little jug- or vase-shaped nests of clay or mud which it attaches to the stem of a plant. It provisions it with caterpillars, often with canker-worms. The social wasps (ves’pide) live in communities in spring, summer, and autumn. The males and: workers die in the autumn, and the females (queens) hibernate through the winter under logs or stones or in crevices. In the spring each queen starts a colony. She makes a small nest containing a few brood-cells, in each of which she Jays an egg. The hatching larvee 182 BRANCH ARTHROPODA are fed by the queen with insects captured, killed, and somewhat masticated by herself. _ In a few days the larve pupate in the cells and soon issue as workers. These enlarge the nest, adding new brood cells, which the queen fills with eggs, which, upon hatching, are fed by the workers. Thus, several broods of workers are reared, and the nest is continually enlarged to make room for the increasing family. Early in autumn a brood is hatched con- taining males and females, which mate probably with individuals of other communities, and at the approach of winter most of the colony dies, leaying only a few hibernating queéns. The nest of the social wasp may be under ground, in which case it is made of partially decayed wood, or it may be attached to bushes or trees or under Fig. 148.—A hornet’s nest, showing two horizontal sections of comb, one above the other, and the many layers of paper surrounding thenest. (Photo- graphed from object.) the eaves of buildings. This wood is formed into a pulp by being masticated with saliva and chewed. In the genus Polis’tes the nests consist of a single cone and are not inclosed in an envelop, but in the genus Ves’pa, including the yellow-jackets and hornets, the nest (Fig. 148) consists of several hori- zontal cones suspended one above the other, yet separated by a considerable space from each other, and the whole enveloped in a waterproof covering of many thicknesses of wasp-made paper, the whole nest forming a globular or cone-shaped ball. When the nest is tobe enlarged the wasps nibble away the inner layers of the enveloping paste and add new layers on the outside. Yellow-jackets and Hornets (Vespa).—In this genus the body of the wasp is rather stout and short and the peduncle is very short. The color HYMENOPTERA 183 is black, spotted, and banded with yellow, from which we are all glad to take ‘‘ warning,” for the sting of a hornet is painful and the nest contains thousands of individuals. The queens are larger than the workers. It may be interesting to know that the males have no sting. They may be further distinguished from the other forms by having seven segments in the abdomen instead of six. The social wasps do not store up food, but continually feed the young ‘throughout the larval stage, which lasts from eight to fifteen days, with partially masticated insects. The adults “‘ feed upon insects or decompos- ing animal substances (fish especially attracts them) and upon exposed sweet substances, such as syrups and preserved fruits.” ‘Bees may be distinguished from all other Hymenoptera by their en- larged and flattened tarsal segments, which, except in the [n’quilines, are provided with an arrangement for carrying pollen. It is said that the hairs (at least on the head and thorax) are branched or plumose, as revealed by the microscope, while those of all other Hymenoptera are simple. The nests of bees are always provided with pollen or honey, or both. The larve when quite young are fed by a substance called “ bee-jelly,” regurgitated by the nurse workers; for the bee colony, like those of other Hymenoptera, consists of three forms: the workers, the males or drones, and the female (queen). ; The short-tongued bees (Andren’ide) are all either solitary or grega- rious, none social. Some of the mining bees, genus Andrena, are almost as large as the honey-bee workers. In grassy fields they sink a perpendicular shaft into the ground sometimes to the depth of a foot or more, which branches off sidewise to the cells. Though each nest is solitary, the females often build close together. The smallest of our bees (Halic’tus) burrows in sand-banks or cliffs. Several females unite to “ make a burrow into the bank, after which each female makes passages extending sidewise from this main burrow or public corridor to her own cells. While Andre’na builds villages composed of individual homes, Halictus makes cities composed of apartment houses.’’! The long-tongued bees (A’pid@) have the lower lip highly specialized for obtaining nectar from flowers. The basal segment of the labial palpus is also elongated. Some of this family are solitary; others, guest-bees; a few, social. Among the solitary long-tongued bees is Megachi'le acu'ta, a carpenter and leaf-cutter, which, if it does not find a convenient crevice or cavity ready made, tunnels out a tubular cavity in wood and builds a thimble- shaped nest at the bottom out of oblong pieces of leaves which it cuts out for itself, and fills it with a paste of pollen and nectar. The egg is then placed upon this food and the opening tightly plugged up with circular pieces of leaves. The little blue carpenter bee (Cerat’ina du’pla) builds its nest in dead twigs of sumach or in the hollows of other plants. The female fills the bottom of the nest with pollen, lays an egg upon it, and makes a partition above the egg out of pith chips made in forming the tunnel. She continues making these cells until the tunnel is nearly full, then she rests in the space above the last cell and waits until the young are grown. When the first one is ready to emerge, it tears down the partition above it and waits till each one has performed the same process, when they are led by the mother into the open air. Comstock says it is the only mstance he knows of a solitary 1 Comstock, p. 666. 184 BRANCH ARTHROPODA t bee watching her nest. The old nest is cleaned out by the whole family and used again by one of them. The guest-bees (/n'quilines) infest the nests of both solitary and social bees, sometimes being unwelcome guests. They have, of course, no worker forms, only males and females, since work is not necessary when they can live off the bounty of others. Those infesting the nests of solitary bees steal into the nest before it is completed and lay their eggs, which hatch before those of the host, and devour the food intended for the young of the rightful owner. Strangely enough, the Inquilines (Pszth’yrus) seem to be welcome, for if they were not the bumble-bees surely would drive them out, for they certainly could. The female lays her eggs in a bumble-bee’s nest, and when the larvee hatch they are cared for by the bum- ble-bees as if they belonged to them. Sometimes the guests very closely resemble their hosts in size and color, but in other cases they are marked very differently. The males resemble the bumble-bees so closely in ap- pearance and structure that it is difficult to determine whether they belong to Psithyrus or Bombus, but the females are easily distinguished, for the pollen-basket of the hind legs has been lost through disuse. There are no workers among the Psithyrus, and if for any reason the supply of the host should fail them, the guests would starve, for they are so degenerate as to actually be unable to work. Kellogg says these guest-bees “are like bumble-bees in so many structural details unnecessary for deception (mim- icry) that they must be looked on as a degenerate offshoot from the Bom/- bide,” that is, as degenerate bumble-bees. The social bees, which are native, belong to the genus Bombus. The bumble-bees, like the ants, live in communities having three kinds of in- dividuals: males, females, and workers. In early spring each queen which has survived the winter by hibernating seeks some unoccupied mole’s nest or mouse’s nest or digs a cavity in the ground for her nest. In this she deposits a ball-shaped mixture of pollen and honey and lays a few eggs, not over twenty, upon it. Then she brings another supply of food and de- posits more eggs. When the first larvee hatch they feed upon the food provided, and when grown each spins a silken cocoon and pupates. ‘These all form worker bees, which enlarge the nest and provide more food. The queen lays more eggs and the workers now enclose the larve in waxen cells. A few cells also are filled with pollen or with honey. ‘The nest may become as large as one’s head and is covered loosely with bits of vege- tation. It usually has two or more openings. ‘‘ Later in the summer males and females appear, and it can be said to the credit of the bumble-bee queens that they are not jealous, but allow the young queens to live with them in thenest.’”’? In early winter all bumble-bees perish except the young queens, which hibernate in some crack or crevice. There are more than fifty species of bumble-bees (Bombus) in the United States. They differ in size and in the arrangement of the black and yellow color-patterns. The honey bee is a native of Europe, but has been domesticated the world over. ‘It has been known and cared for by men for centuries. There are two genera: (1) Melipona, which has the sting blunted and ap- parently never used as a weapon, lives in the tropics and consists of numer- ous species which have been little studied. (2) Apis has but few species, one of which is our common hive bee. The community consists normally of one queen, from less than a hundred to several hundred males, and from about 10,000 workers in winter to 50,000 insummer. ‘The queen (Fig. 149, K) may be known by her long slender ab- HYMENOPTERA 185 domen and by the absence of wax plates, planta, and pollen baskets. The queen is hatched from a fertilized egg in a large cylindric, vertical cell (Fig. 149, 6-10), and fed almost wholly upon bee-jelly regurgitated by the - nurse workers. Here, at least, is one strong example of the influence of environment during development, for it has been proved that there is no difference between the egg from which the queen is developed and the one which develops into the worker. The workers (Fig. 149, 4), which are the bees we commonly see, are smaller than the queens and males. They are hatched in hexagonal, horizontal j é ; ay 2 ay oy i leet Petri ne st lialatne ° = bill ees z z| Fig. 149.—Hive bees and comb (after Schmeil). A, Worker; K, queen; D, drone; 1, worker with cells filled with honey and covered; 2, cells con- taining eggs, larve, and pups; 3, cells containing pollen; 4, below 4 are regular cells; 5, drone cells; 6-10, queen cells. cells, and fed, like the males, with honey and bee-bread. ‘‘ Workers have wax plates under the abdominal segments and pollen baskets on the outer surface of the hind tibiz.” The males, or drones (Fig.-149, D), have a hairy thorax and a heavy, broad, blunt body, and, like the queen, lack the special structures of the’ workers. They are hatched in the larger, hexagonal, horizontal cells from “unfertilized ” eggs. After the swarming season is over, the males are driven out of the hive or stung to death by the workers. When a community becomes too large, the workers prepare a “‘ queen- cell” and develop a queen by process of special feeding and care, or, it ‘ 186 BRANCH ARTHROPODA may be, several queens are so developed. When these young queens emerge, the old queens at once enter into battle with them. All new queens are killed but one, which the workers guard. The old queen leaves the hive accompanied by a swarm of workers and founds a new colony. The work- ers at once begin to secrete wax by gorging themselves with honey and then together “‘ hang quietly in a curtain-like mass, the upper bees clinging to the roof of the hive and the lower ones to the bees above them. After about twenty-four hours there appear little flakes of wax that are forced out from openings between the ventral abdominal segments, called wax- pockets. These wax scales continue to increase in area and soon pro- ject beyond the margin, and either fall off or are plucked off by other workers or by the wax-producing worker itself.”’! Other workers construct it into comb, the trowel-like mandibles pressing it into hexagonal cells. Hach comb consists of a double layer of cells separated by a common partition. New wax is used in forming cells for storing honey, but old wax or wax mixed with pollen may be used for brood-cells. The workers also carry “ propolis,” a sticky, gummy substance with which they at once stop the chinks of their hive. They carry water also to the thirsty larve. By steadily and rapidly vibrating their wings a set of workers stationed at the exit or scattered about the floor form currents of air, thus ventilating the hive. Another set acts as scavengers and carry off all dead and decaying débris from the floor and walls. Still another set guards the entrance from intruders, such as neighboring bees, yellow-jackets, and bee-moths. For guarding against the minute bee-lice and bacterial diseases the help of man, “ the bee-keeper,” is needed. Kellogg gives an observation hive and how to make it, which would be well worth trying. For after you have studied carefully these, shall I say, intelligent little creatures you will find it, indeed, difficult to decide which of their actions are reflex, instinctive, or intelligent, or which are all of these combined. Classification.— Class I. Crusta’cea. Sub-class Hn’tomos’traca. Order I. Phyllop’oda. Brine shrimp. Daphnia. Order Il. Ostrac’oda. Cypris. Order III. Copep’oda. Cyclops. Order IV. Cirripe’dia. Barnacles. Sub-class Mal’acos’traca. Order I. Phyllocar’dia. § Nebalia. Order II. Decap’oda. Crayfish, lobsters, crabs. Order II. Arthros’traca. Gammarus. Pill-bug. Class II. Arach’nida. Order I. Scorpion’ida. Scorpions. Order II. Phalangi’da. “Daddy-long-legs.”’ Order Ill. Arane’ida. Spiders. Order IV. Xiphosu’ra. Limulus or Horseshoe Crab. 1 Kellogg, p. 526. HYMENOPTERA 187 Class HI. Myriap’oda. Order Ti Order Il. Class IV. Insec’ta. Order ig Order Its Order III. Order IV. Order V. Order VI. Order VII. Order VIII. Order IX. Order XM Order OE Order XII. Order XIII. Order XLV; Order XV. Order XVI. Order OV LE Order XVIII. Order XIX. Chilop’oda. Diplop’oda. Ap’tera, or Thys- anu’ra. Ephemer’ida. Plectop’tera. Odona’ta. Tsop’tera. Corroden’tia. Malloph’aga. EKuplexop’tera. Orthop’tera. Physop’oda. Hemip’tera. Neurop’tera. Mecop’tera. Trichop’tera. Lepidop’tera. Coleop’tera. Dip’tera. Siphonap’tera. Hymenop’tera. Centipedes. Millipeds. “Fish-moth” and “spring tails.” May-flies. Stone-flies. Dragon-flies. Termites. ‘“‘Book-lice.”’ “Bird-lice.”’ Earwigs. Grasshopper, katy-did. Thrips. Chinch-bug, plant lice, and cicada. Aphis-lion, ant-lion. Scorpion-flies. Caddice flies. Butterflies, moths. Beetles. Flies. Fleas. Ants, wasps, bees. BRANCH CHORDATA Branco Chordata comprises many of our best-known and valued animals. un & 11 II FIsH- SalAMANDER: — TORTOISE: Fig. 150.—A series of embryos at three comparable and progressive stages of development (marked I, II, III), representing each of the classes of vertebrated animals below the Mammalia. (After Hackel.) 188 BRANCH CHORDATA 189 Characteristics.—They all have (1) Gill-slits in their embry- 1 I Hog. CAUr. RABBIT. MAN. Fig. 151.—A series of embryos at three comparable and progressive stages of development (marked I, I, III), representing four different di- visions of the class Mammalia. (After Hackel.) onic life or they may be permanent; (2) a notochord; (3) a nerve chord or nervous system dorsal to the notochord. The noto- 190 BRANCH CHORDATA chord is a smooth, elastic rod typically developed from the endo- derm, extending along the median line between the alimentary tube and the central nervous system. It is encased in a tough sheath or membrane and “‘forms an elastic supporting structure.” PlsAetgloel I) as AG a nee an ps NJ a a Boot eb he shared — ae NU SX mr kg Fig. 152.—Ideal primitive vertebrate, seen from the left side: na, Nose; au, eye; md, mouth; g, ear; ks, gill openings; x, notochord; m7, spinal tube; kg, gill-vessels; k, gill-intestine; hz, heart; ms, muscles; ma, stomach; v, intestinal vein; c, body cavity; a, aorta; 1, liver; d, small intestine; e, ovary; h, testes; n, kidney-canal; af, anus; lh, true or leather skin; oh, outer skin (epidermis); f, skin-fold, acting as a fin. (After Hackel.) In the higher forms the notochord is replaced by a segmented cartilaginous or bony vertebral column. These three characteristics may not be easily recognized by the beginner as he looks at the worm-like Bal/anoglos’sus, the Fig. 153.—The same in transverse section through the ovaries; lettering as in the preceding figure. (After Hiackel.) sac-like sea-squirt, or the small fish-like or worm-like Am’phiox’us or Lance’let, but, passing by these low forms to the fishes, frogs, reptiles, birds, and mammals, one readily finds that the body has two cavities instead of one, as in the invertebrates. ADELOCHORDA 191 Neural Cavity.—The upper or neural cavity contains the brain and the spinal cord. Hemal Cavity.—Below the vertebral column with its neural cavity is the large cavity of the body, the hemal cavity, which contains the heart, lungs, digestive organs, and other viscera. - Skeleton.—Most of these higher forms have an internal bony skeleton or a cartilaginous one, as in some fishes. The vertebral column, or backbone, is composed of a varying number of bones, each called a vertebra, hence the branch is named Vertebrata, or, if named from the notochord, Chordata. Divisions of the branch are usually made to distinguish the primitive groups (Fig. 152) or Protovertebrates, from the true Vertebrates. The Protovertebrates consist of three separate groups or sub-phyla, not closely related to each other, but each, in a primitive way, is entitled to relationship with the Chordata or Vertebrata. SUB-PHYLUM AND CLASS I. ADELOCHORDA The Balanoglossus is the principal genus of this group, though two deep- sea forms (Rhabdopleu'ra and Ceph’alo- - dis’cus) have a notochord, and the latter has a pair of gill-slits, but in other ways they are like the polyzoans. The Bal- anoglossus (Fig. 154) is a small marine chordate. Its surface is ciliated. It is from 1 to 4 or 5 inches in length, and, by Fig. 154.—Balano- : p, Proboscis; 15 gs) gill slits; enlarged. (From Dodge’s ‘‘ General Zo- ology,” American Book Co., Publishers.) means of its proboscis, burrows in the mud along the seashore. A study of the animal or of a good figure will show that it has (1) a dorsal nerve cord, (2) a notochord, and (38) gill-slits. Body Regions——The Balanoglossus is divided into three body regions: the proboscis, a club-shaped hollow anterior por- tion opening exteriorly by a single pore; back of the proboscis 192 BRANCH CHORDATA is the collar, opening by two spores into the first gill-slit; the re- mainder constitutes the flattened but nearly cylindric trunk. There is no segmentation of the body. By alternately contract- ing and dilating the proboscis and the collar the Balanoglossus can burrow in the mud. Gill-slits —On the dorsal surface of the anterior portion (the branchial region) of the trunk is a double row of gill-slits which increase in number throughout life. Digestive System.—The mouth is situated ventrally at the base of the proboscis just within the collar, and fromit the alimentary canal extends to the posterior extremity of the body. ‘Into the dorsal half of the anterior portion of the alimentary canal open the internal gill openings.”” The hepatic ceca bulge out in ex- ternal prominences in the middle part of the canal. The anal opening is at the posterior end of the body. ~ The notochord, ‘“‘a blind tube surrounded by a tough mem- brane, extends from the pharynx into the proboscis.”” There are dorsal and ventral nerve strands connected by nerves in the collar. A dorsal blood-vessel lies above the notochord. The larvze of some species so much resembles certain echino- derms that the Balanoglossus was formerly placed with that branch. SUB-PHYLUM AND CLASS II. UROCHOR’DA OR TUNICATA This degenerate group is represented by minute animals a few centimeters long and by some measuring several feet in length. They are found singly or in string-like colonies which have been developed from a solitary individual by budding, the two forms thus giving rise to alternation of generations. Multiplication is both sexual and asexual. They are hermaphroditic, but cross- fertilization occurs. They are marine and most of them are pelagic. The most common forms, the ‘‘sea-squirts” or ascidians (Fig. 155), are surrounded by a tough elastic bag, one end of which is attached to stones. At the other end is a large round oral aperture, for the inlet of water carrying food and air, and near it, UROCHORDA OR TUNICATA 193 on one side, is the atrial aperture, for the exit of the current. Sea-squirts are destitute of head and limbs. The ventral heart enclosed in a pericardium is situated between the gill region and the stomach. This heart has the peculiarity of changing the direction of its contractions. When the blood has been driven to the gills for a while it rests a little, and then forces the blood in the opposite direction. ead Fig. 155.—Diagram of the growth of a see eo or ascidian: A, a, young free-swimming stage; a?, intermediate stage just before becoming fixed. B, 6, Full-grown sea-squirt, rooted to the sea bottom and incapable of movement: m, mouth; e, hollow brain with eye; g, gill-slits; h, heart; r, rod of gristle in free-swimming form; nv, nerve cord in same; t, tail in process of absorption in intermediate form. (After Haddon.) (From Baskett, “The Story of the Fishes,’ D. Appleton and Co., Publishers.) The “sea-squirts’”” were formerly called ‘“Tunicates,” until a study of their larval stage showed them to have vertebrate char- acteristics. The larva has a slender finned tail containing a notochord and a nerve cord. They furnish an example of retro- grade development. ‘They are free for a few hours, then be- come fixed and lose the notochord and nearly all traces of their vertebrate characteristics which promised a higher develop- ment. 13 194 BRANCH CHORDATA SUB-PHYLUM AND CLASS III. ACRA’NIA OR AMPHIOXUS This is a small fish-like chordate 2 or 3 inches in length. Its shape is one found for the first time, that of narrow ventral and dorsal sur- faces and deep lateral surfaces. It is pointed at both ends. It falls on its side when not in motion. It is marine and lies buried in the clean sand along warm seacoasts, with its ciliated lips protruding. The currents produced by the cilia bring fresh water with its oxygen to the gills. Small organ- isms are also thus furnished for food. The Am’phiox’us (Fig. 156) has no limbs, no skull, no well-differentiated brain, and no heart, but it has a noto- chord (a smooth cylindric rod lying above the alimentary tube), a nerve cord dorsal to the notochord, numerous gill-slits, and an alimentary tube. The sexes are separate. The alimentary tube is a straight tube consisting of mouth, pharynx, and in- testine. On the right side of the pharynx is ablind pouch, the so-called liver. The circulatory system consists of a dor- sal arterial trunk and a ventral venous trunk connected by lateral arches. The blood is colorless. AWN 3) Loy Ss po tou CCK ut ( me eeeeti aunt COC Ka Fig. 156.—Amphiox’us lanceola'tus : a, Anus; au, eye; b, ventral muscles; c, body cavity; ch, notochord; d, intestine; do and du, dorsal and ventral walls of intestine; f, fin-seam; h, skin; k, gills; ka, gill-artery; [b, liver; lv, liver-vein; m}, brain vesicle; m?, spinal marrow; mg, stomach; 0, mouth; p, ventral pore; r, dorsal muscle; s, tail fin; ¢, ¢, aorta; v, intestinal vein; x, boundary between gill intestine and stomach intestine; y, hypobranchial groove. (After Hackel.) CYCLOSTOMATA 195 Locomotion.—TYhe Amphioxus has a median dorsal fin which extends over the tail both dorsally and ventrally. The tail, that portion of the body posterior to the alimentary tube and filled with muscle, is the chief organ of locomotion. It is noc- turnal, swimming about at night, but quickly returns to its burrow if disturbed. It can burrow in the sand with either head or tail. Nervous System.—A simple dorsal nerve lies above the noto- chord. It does not reach entirely to the front of the body. Its anterior tip is called the cerebral vesicle, in which there is an eye-spot. ‘There is also possibly an olfactory organ consisting of a simple pit reaching from the skin down into the anterior tip of the nerve cord. SUB-PHYLUM IV. CRANIA’TA OR VERTEBRA’TA These are chordates having a brain or skull. The group includes fishes, amphibians, reptiles, birds, and mammals. The body is usually elongated and more or less cylindric. The mouth is situated anteriorly. Ventrally and near it, ex- cept in Cyclostom’ata, are the paired nostrils. Situated in the head there are alsoa pair of eyes and a pair of ears, though the ears are not always external. Gill-slits are never more than seven in number, and partially or alto- gether disappear in the adult air-breathing forms. There are one or two pairs of jointed limbs, but in some cases they are rudimentary or wanting. CLASS I. CY’CLOSTOM’ATA The animals of this class inhabit both fresh and salt water. They have no lower jaw. The mouth is suctorial, the skull cartilaginous, the notochord persistent, and the teeth horny. The neural arches are rudimentary. There are no limbs or scales and no paired fins; but unpaired dorsal and caudal ones are present. The class includes the lampreys (Fig. 157) or “lamprey-eels’”’ and the hag-fishes. The skin is 196 BRANCH CHORDATA © slimy and very smooth. The gills of the lampreys open into a respiratory tube lying below the gullet. They are parasitic on fishes and also devour crustaceans. The slimy eels bore into fishes and eat the flesh. CLASS II. PIS’CES To this class belong the true fishes, common examples of which are the sunfish, perch, salmon, catfish, carp, and trout. They are aquatic, gill-bearing, poikilothermal, usually scaly, bilaterally symmetric finned chordates. Shape.—The typical fish is wedge shaped (Fig. 158) at both ends, so that it can pass rapidly through the water. The head is large and pointed, with the viscera situated near it, while the trunk is long and tapering, for the attachment of muscles to flex the tail in locomotion. Usually the body is more or less flat- tened from side to side, though it may be quite cylindric, as in the eel, or flattened dorsoventrally, as in the adult flounder, or the body may be long and slender, as in the pipe-fish and ribbon- fish. The shape conforms largely to the habits and habitat. The fishes having the under side flattened usually swim near or rest upon the bottom at some time, as our catfish, but the broad forms, flattened above and below, like the skates and flounders, live upon the bottom and are not built for speed. The “‘flat fishes” in early life have the position common to most fishes, but in adult life the dorsoventral plane becomes horizontal instead of vertical, the eye lies upon the upper side, and the color of the upper side becomes dark like the dorsal side of most fishes, and — the under side light like the ventral side. PISCES 197 Size and Number.— Fishes vary in length from an inch or less to 30 or 40 feet. Kellogg says there are about ‘15,000 species of fishes known, of which 3000 species live in North America.” Is it any wonder they vary in size, color, and habits? They are the best adapted of all vertebrates for an aquatic life. Covering.—The epidermis consists of many layers of proto- plasmic cells with a very thin cuticle. The secretion of mucus by the great numbers of “‘slime-cells” of the epidermis gives to fishes their slippery skin. The epidermis contains also pigment cells. The dermis consists of numerous layers of connective Fig. 158.—Figure of a whitefish, showing the location of parts usually referred to in descriptions: 1, Dorsal fin; 2, adipose fin; 3, caudal fin; 4, anal fin; 5, pectoral fin; 6, ventral fin; 7, lower jaw, or mandible; 8, upper jaw, or maxillary; 8a, supplemental maxillary; 9, opercle; 10, branchioste- gals; 11, caudal peduncle; 12, lateral line; 13, series of crosswise scales usually counted; 14, snout; 15, eye; 16, head; 17, depth; 18, base of caudal; 19, dis- tance from snout to nape or occiput. (Report U.S. F. C., 1894.) tissue and furnishes the dermal or exoskeleton or scales which are usually embedded in pockets of the dermis. In many fishes the scales overlap each other. In the brown trout, for example, the greater portion of each scale lies under the one anterior to it, and the remainder, a small triangular por- tion, is covered by the epidermis only. The scales sometimes receive a layer of enamel or vitrodentin from the epidermis. (1) The placoid scales are rhombic, plate-like bodies often bearing a spine covered with vitrodentin. These scales are placed close together, but do not overlap. (2) The ganoid scales also are 198 BRANCH CHORDATA generally “rhomboid and arranged like parquetry.”’ They are covered with a thick coating of vitrodentin which gives an iridescent effect, and are often closely articulated into a coat of armor. (38) The cycloid scales are closely related. They are placed loosely in the pockets and arranged in rows. . In over- lapping, one scale covers parts of two scales posterior to it. The middle part of the scale is surrounded by concentric lines from which proceed radiating lines. (4) The ctenoid scales (see Fig. 174) have the posterior edges truncate and the free margin toothed. The scales are often striated or polished, and this gives rise to various colors, especially the iridescent gleam on the sides of the fish. Color.—The color in general harmonizes with its environment. Most of the fresh-water fishes are dark colored (olive or greenish) above and whitish below, so that to the enemies from above, as fish-eating birds, the form appears indistinct in the water, and to the enemies below they look white like the light. Many are variously dotted or striped with lighter or darker colors, thus simulating the lights and shadows among the weeds and grasses. The scales reflect all the hues and tints of the rainbow, causing the fishes to rival the birds in beauty. The males of some species put on brighter colors at the spawning season. Some species have the power of changing color at once to meet the surround- ings, as the pipe-fishes, some sticklebacks, the plaice, and the little Oligocottus snyderi, of Monterey Bay, California. Many others change the colors more gradually. Recent experiments upon fishes in aquaria have shown that if the light be thrown from below and cut off from above, the upper part grows light colored and the lower part dark colored. This would seem to show that the colors are due to the action of light, but while many fishes in caves are colorless, it is said that those in the black depths of the ocean may be either pearly white or black; so the question is yet unsolved. Many deep-sea forms are phosphorescent. Some fishes have special protective resemblance, as the leaf- finned sea-horse, the pipe-fish, and some angler-fishes, the pos- terior fins of which are bedecked with fringes “‘that exactly mimic seaweed.” The mouse-fish, or Sargassum, is colored to harmonize with the gulf weed, Sargassum, among which plants it lives. PISCES ~~ “199 “ The color of fishes is of threefold origin, The silvery luster is due to erystals of guanin which occur in the skin. The other colors are due partly to numerous strongly pigmented fat-cells and partly to the chro- matophores in the derma, which under the control of the nervous system can alter their forms and extent and thus produce color changes in the fish, thus adapting it to its surroundings. It is of interest to note that destruction of the eyes results in loss of power to change color.’’! Locomotion and Appendages.—The appendages of fishes, ex- - cept in rare instances, are the unpaired dorsal, anal, and caudal ‘fins, and the paired pectoral and ventral fins. ‘Fishes are the only vertebrates having median fins supported by fin-rays.”’ The fin-rays supporting all the fins are of dermal origin. The locomotion is mainly produced by the flexing of the body and tail, so as to propel the usually spindle-shaped animal through _the water. The fins aid in directing the movements of the fish, as does also the air-bladder, which regulates the specific gravity of the fish. The skeleton is cartilaginous or bony. The notochord of the protovertebrate becomes surrounded by a mesodermic sheath | which produces the centra of the vertebra, consisting of cartilage or bone. From the centra are outgrowths dorsally which give rise to the neural tube, “an inverted tunnel of cartilage” en- closing the cerebrospinal cavity, and ventral (hemal) outgrowths protecting the viscera. The vertebre are usually amphicelous, and the notochord persists in the cavities between the centra. The neural arches extend throughout the spinal column, while the hemal are complete only in the tail. In the trunk the hemal spines are absent and the hemal processes are divided into basal processes and ribs which surround the viscera. There is no sternum. The skull (Fig. 159) encloses the brain which does not fill the cavity. The lower jaw is movable and usually bears teeth. Some fishes have many teeth; others, few or none. They have no other prehensile organs. The pectoral and ventral fins are homologous with the paired limbs of the higher vertebrates, but lack many of the bones of the higher forms, as a comparison of the bones of man’s arm with those of the pectoral fins will show. 1 Hertwig’s “ Manual of Zoélogy,” Kingsley, p. 559, 200 BRANCH CHORDATA Digestive System.—The food is principally animal. Food securing is, of course, by the mouth. The mouths of fishes vary in size, shape, and position, according to the food and feeding habits. The digestive tract is large, near the region of the phar- ynx, but narrows into a tube in which there is little distinction : “Ast Byplzl ae ms ss pe, 997 —y Ventricle of the heart ae ’ Auricle of the heart-.../ / Venous sinus*--7 -Kidneys Dorsal artery or aorta Fig. 160.—The circulatory apparatus of a fish. (Tenney.) venosus, from which it passes through the parts of the heart in the order named, and the circulation begins anew. Respiration is by gills except in the lung fishes, which take the mechanically dissolved air from the water and give off waste matter. The gills arise as paired pouches of the pharynx and open on the exterior by gill-slits. They are attached to the branchial arches and are persistent through life. 202 BRANCH CHORDATA The brain is of the vertebral type, but small, and occupies but a small portion of the cranium. The cerebrum is comparatively small. The cerebellum is sometimes large. The optic and ol- factory lobes are conspicuous (Fig. 161). The medulla is also present, all the parts being distinct and visible from above. The brain sends off at least ten pairs of nerves. The Senses.—Of all the sense organs, the most noticeable are those along the — lateral line. The lateral line on either side of the fish from tail to head is “marked by a groove in the scales which opens to the exterior by numerous canals through the scales.” (Examine several scales along the lateral line.) The func- tion of the lateral line is possibly to as- Bigs 160 Brain) of certain the water pressure at different a cod: og, Olfactory depths. ganglia; ch, cerebral The skin and especially the lips are hemispheres; ol, optic lone; @ wexssellvcn: the seat of the sense of touch. mo, medulla oblongata. The eye has several peculiarities. The (Tenney.) lens is very convex, owing to the slight re- fraction from the light in passing from the water into the cornea. The eye is short sighted, since light is so absorbed by water as to render objects a short distance away invisible. Lids are wanting or very poorly developed. Only Fig. 162.—Lucifu’ga. A blind fish containing unborn young with well- developed eyes. (EHigenmann, Bulletin 526, U.S. F. C., 1902.) a few fishes have a nictitating membrane. There are no tears. Through disuse for generations the cave fishes have lost their sight (Fig. 162). PISCES 203 The ear! has a relative size found in no other vertebrate. There are no external ears. Many teleosts have two otoliths. Experiments show that the ear is principally for a balancing organ. = Fig. 163.—Stickleback and nest. (From Baskett, ‘“ The Story of the Fishes,” D. Appleton and Co., Publishers.) 1“The maigre is said to produce a flute-like note audible in twenty fathoms. Many fishes utter sounds, but perhaps the grunt (Hemulon) on the outer Florida reef is most remarkable for the variation of the sound. . . . The dog-fish utters a croak or bark. The gizard-shad (Hippo- campus), eels, catfish, porcupine-fish, sunfish, carp, gurnards, etc., utter sounds either accidental or intentional. The sound, a single note, fre- quently uttered by the eel is, according to Abbott, more distinctly mu- sical than those made by other fishes.” (Holder.) 204 BRANCH CHORDATA The function of the nostrils is smelling and not breathing, For none of them, except those in the hag-fish and lung fish, open into the mouth. The odors must come through the water. All fishes proper have two nostrils. Experimental proof of smell is lacking, but the well-developed olfactory lobes and nerves argue that the sense cannot be entirely wanting. Emotions.—If you have ever tried the sport of fishing with hook and line, you know that fishes have emotions of fear and curiosity. Romanes says they have also those of play, anger, pugnacity, and jealousy. In some species parental affection is proved by the building of nests (Fig. 163) and the care of the young; sexual feelings, by courtship; social or gregarious in- stincts, by their ‘‘schools.”’ ! Fig. 164.—Sawfish. Upper, profile view. Lower, viewof under part. (Pristis pectinatus.) Means of Defense.—Fishes most often protect themselves from their enemies by their close resemblance to the surround- ings, or by their swift movements, darting away at the least in- timation of danger. But many are also armed with weapons of defense, such as the spines connected with the fins of the dog- fish and the catfish. The mucus which flows over the spines is somewhat poisonous, making the wound painful. The “Scorpanoids” have a little poison sac on each side near the tip from which the poison flows down a groove of the spine into the wound. The Thallassophryne has, besides the dorsal hollow poisonous spines, in which the poison sac is situated at the base, non-poisonous spines on the gill-covers. The poreupine-fish (Di’odon macula’ta) and the globe-fish (Chylomyc’terus geome’ tri- cus) have spines all over the body. The “surgeons” and rays 1 Baskett. PISCES: 205 have spines on the tail. The thresher-shark (Alo’pias vulpes) has its pliable tail prolonged into a terrible weapon, with which, it is said, it can kill a whale. This lashing tail serves a second purpose by so frightening the small fishes that they crowd to- gether and are thus easily obtained for food. The “‘devil-fish” - strikes terrible blows with its broad pectoral fins. The saw-fish : ; y ery ‘Re, Fig. 165.—Sword-fish (Tetraptu’rus), yellow-fin tuna, and yellow tail, caught with rod and reel at Santa Catalina Island. (Bulletin of B. of F., vol. xxviii, 1908.) . (Fig. 164), sword-fish (Fig. 165), and the like use their long strong jaws as frightful weapons. The torpedo and other electrical fishes surprise and stun their victims by an electric shock. Influence of Temperature.—Species differ in their ability to endure cold or heat. The brook trout loves the cool water of 206 BRANCH CHORDATA the mountain streams, while the catfish can live in exceedingly warm water. “Fishes have been found in hot springs of 120° F.” The Protop'terus of Africa and Asia “‘so completely slimes a ball of mud around it that it may live thus for more than one season.’ Other fishes bury themselves in the mud and estivate through the dry season. The little “mud-skippers”’ move from pond to pond by the use of their pectoral fins. Other fishes migrate to cooler waters as necessity requires. In winter some of the fishes of our small streams hibernate in the mud, while some, as the carp, may have the water frozen into ice about them and live when thawed out. Development.—The sexes are separate. Multiplication is by eggs, which are numerous. The cod is said to lay one million eggs. In the bony fishes the eggs are naked and numer- ous, and fertilization. usually takes place in the water. In sharks the eggs are few and are protected by a horny shell. In most sharks and in a few bony fishes the eggs are fertilized and hatched within the body of the mother fish. Mating takes place in a few viviparous forms only. Most fishes do not care for their young “‘fry,” but the stickleback builds a nest and de- fends it with great courage. There is usually no metamorphosis, but some ocean species change almost as much as frogs. SUB-CLASS I. ELASMOBRAN’CHII The rays and sharks represent the Sela’chii, in which are found all the living elasmobranchs. They have no operculum (gill- cover) and no air-bladder. The skeleton is cartilaginous. The mouth and nostrils are ventral and the tail heterocercal.? The scales are small. “The cloaca is the common outlet for the rectum, renal and reproductive ducts.’’ Some are viviparous, others lay a few eggs, each enclosed in a chitinous case. Sharks vary in length from 2 to 60 feet, the majority being under 8 feet in length. Some are large and voracious, a few dangerous even to man. Hornaday says the only loss of life from sharks on our coast occurred in 1830. They feed mostly upon fishes. The rays (Rav’ide) have Tne body disk shaped, broad, and flat, 1 Baskett. 2 Glossary. HOLOCEPHALI 207 the pectoral fins being much expanded. The skin is roughened by spines or prickles. Rays most generally live on the bottom of the sea, feeding upon fishes, mollusks, crabs, and other bot- tom-frequenting animals. To the order Sela’chi belong the skates (Fig. 166), sting-rays, and torpedoes or electric-rays. The saw-fish ray also belongs to this order. Its formidable, sharp-toothed snout, several feet in length, makes it a dreaded enemy. It disables its prey by dashing into a school of fishes, striking right and left. Then it eats its dis- abled prey at leisure. SUB-CLASS II. HOLOCEPH’ALI \ This group : is represented Fig. 166.—Common skate (Ra’a on our Atlantic coast by the erinacea.) Chimera monstro’sa (Fig. 167). The Holoceph’ali were formerly abundant, but are now repre- sented by only a few genera. The skeleton is cartilaginous and the skin is smooth. These are very peculiar looking fishes, as a glance at Fig. 167 will show. The nostrils and mouth are ven- —— Fig. 167.—Chime'ra monstro’sa. (Claus.) tral. In general they resemble the sharks in their compressed form, but differ from them by the large head and small mouth. ‘Fossil remains are found from the lower Jurassic rocks upward.” 208 BRANCH CHORDATA SUB-CLASS III. DIP’NOI The “lung fishes” are snake-like or eel-like (Fig. 168), and bear small, soft, cycloid scales, small paired fins, and a diphycer- MH ea NN Ged <7 J \\ a N viel i , H x al a) Ih Aly Fig. 169.—The Cer’atodus of Queensland, an air-breathing and water- breathing mudfish of the ancient type, with paddle fins. (From Baskett, “The Story of the Fishes,” D. Appleton and Co., Publishers.) cal caudal fin. The skeleton is largely cartilage and the noto- chord persistent. They live in fresh water, and usually breathe TELEOSTOMI 209 by gills, but when the water gives out or becomes unfit for use the swim-bladder, which may be single or double, is used for lungs. It opens into the ventral side of the gullet and contains air-cells. In this case the air enters through the nose. They are interesting as showing how land forms may have originated from aquatic forms. There are only three existing genera: the Lepidosi’ren, of the Amazon; the Cer’atodus (Fig. 169), of Australia, and the Protop’terus, of Africa. The Protop- terus (see Fig. 168) ‘‘can live out of water, it burrows in the mud at the dry season and builds a cocoon lined with mucus in which it remains quiescent until the wet season.’”! SUB-CLASS IV. TELEOS’TOMI To this extensive sub-class belong our bony fishes, including most of the living fishes. It contains thousands of species. Fig. 170.—Remoras and shark, showing dorsal fins modified into sucking disks, by which the remora attaches itself to the shark in its commensal life, thus securing free transportation. (From Baskett, “‘ The Story of the Fishes,” D. Appleton and Co., Publishers.) Familiar examples are the perch, sunfish, catfish, trout, carp, pike, cod, and salmon. The mouth is terminal. The nostrils are on the upper surface of the snout. The tail is homocercal 1 Hertwig. 14 210 BRANCH CHORDATA (see Fig. 170, Rem’ora), the scales are either ctenoid or cycloid. These fishes vary in shape. They vary in size from our little darter, 13 inches in length, to the “horse-mackerel,’”’ which may weigh as much as a cow. They differ in habits from the pre- daceous, swift pikes and pickerels to the peculiar flounder on the bottom of the sea. The Remora (Fig. 170) is a lazyfish. It has a sucker on. top of its head, by which it holds fast to sharks or larger fishes, and thus saves itself the effort of locomotion. Order I. Crossopteryg’ii.—There are only two existing genera, Polyp'terus and Calamoichthys, of Africa. Order II. Chondros’tei (Sturgeons) (Fig. 171).—They have paired fins with no basal lobe, supported by dermal rays. The pelvic fins are abdominal. The vertebral column consists of the notochord with cartilaginous arches. The tail is heterocercal. Fig. 171.—Common sturgeon (Acipen’ser stu’rio). (Report U.S. F. C., 1899.) The mouth is ventral, projectile, and toothless, and sucks up worms and larve from the muddy bottom. The surface is roughened by separate scales and by five rows of bony plates. Sturgeons are found in streams and lakes of the Northern Hemisphere and are the largest fresh-water fishes. Those of the lower Columbia River sometimes weigh from 800 to a 1000 pounds. From the swim-bladder of the sturgeon, glue, cement, court- plaster, and isinglass are made. The egg-masses, called roe, furnish caviare. Order III. Holos’tei—F amiliar examples of this order are the gar-pike and the mud-fish, often called dog-fish, of the streams of the central states. The skull is ossified. The scales are ganoid or cycloid; the tail, diphycercal or homocercal. The pelvic fins are abdominal. TELEOSTOMI 211 The spiral valve is present. The double air-bladder aids in breathing. The gar-pike (Fig. 172) has a cylindric body covered by rhomboid, bony scales, which are coated with enamel. The snout is long and bony and armed with sharp teeth. This fish is voracious. There are three species found in the fresh water of North and Central America, including Cuba. They are from 5 to 10 feet in length. TASSSERSES SSS SS = WMA. AG Y; 4 7) NYS uss Fig. 246.—Pheebe. (Bulletin 17, U. S. Biological Survey, 1902.) Of the thirty species that breed here, not more than-a half dozen are permanent residents of the temperate region. They feed on insects, mostly injurious ones, which they catch while on the wing. The true larks (Alaw’dide) are chiefly Old World birds, there being about 100 species in Kurope, most notably the skylark. We have only about a dozen of this family, the horned and shore larks. The ‘‘ meadow-lark ”’ belongs not in this family, but with the blackbirds. Of the crows and jays (Cor’vide) we have about twenty-five of the two hundred species. They are migratory only to a certain extent, being winter residents except in the North. They are omnivorous, eating fruits, seeds, insects, and, in some cases, the eggs and young of other birds. This last habit is by far their worst one. They have unusual intelligence, 302 BRANCH CHORDATA The orange and black Baltimore oriole (Fig. 247), one of the most beauti- ful, as well as useful, of our summer birds, destroys many tent caterpillars and other hairy larve which few birds will eat. If one has ever known his rich, clear whistle, one can never forget it or fail to recognize it when the ‘bird arrives about the first week of May. The delicate hanging nest, which the female weaves of grass and hair and strings, is a marvelous ac- complishment. It is suspended far out near the end of a small flexible twig, where cats and boys cannot come. The elm is a favorite nesting tree. Fig. 247.—Baltimore oriole attacking nest of American tent caterpillar. (Bulletin 75, 1900, New Hampshire Coll. Exp. Station.) Grackles or blackbirds are common summer residents. They are said to have the same bad habit as the jays and crows, of eating the eggs and young of other birds, though they eat also many injurious Insects. The cowbird lays its eggs in the nests of other birds. It should be killed and its eggs destroyed. The largest family (Fringill’ide) of birds (about 500 species), containing the finches, sparrows, and grosbeaks, is represented everywhere except in the Australian region. They are chiefly seed-eating (Fig. 248) and so are less migratory than insect-eating birds. The sparrows are plain-inhabiting and are protectively colored, while the more arboreal grosbeaks and finches are rather brilliant. 303 2, white- b) (Bulletin 17, Biological destroying sparrows: 1, Junco E 2 n cI o ea fa) any Z St = UES A oon DH © ash fo} Nees ey BS penis, OO BEA lo) Be. | Ba =) Fig. 248 throated sparrow Survey, 304 BRANCH CHORDATA Although the tanagers are distinctively American, only five of them come so far north as the United States. They are remarkable for their brilliant plumage. When one sees the tanager in his royal or ‘‘ court costume”’ one feels that this beautiful bird of summer has indeed put brightness into that day. Tanagers are arboreal, loving the woods. They feed on flowers, fruit, and insects. Swallows (Hv’rundin’ide) have a remarkable power of flight.’ In summer they are found throughout North America. Our barn swallow in winter goes as far south as Brazil. The number of injurious and annoying insects which they catch on the wing is almost beyond imagination. The wax-wings (Ampel’ide) (Fig. 249) are found in the northern parts of both the Old and New Worlds, though there are but three species. They feed chiefly on wild fruits and insects, including the elm beetle. They are Fig. 249.—Cedar wax-wing. (Biological Survey, U. S. Dept. Agricul.) usually found in small flocks. Their common notes are a few unmusical calls, which our cedar wax-wing usually utters when about to fly.!. The quiet beauty of these birds is beyond all description. The warblers (Mniotil’tide) are characteristic North American birds and number more than 100 species, of which 70 visit the United States. The others are tropical. With us in the temperate region they are only birds of passage, making us brief but regular visits in May as they go to their northern breeding ground, and again in September as they return to the southland. Most of them are woodland birds. Some are terrestrial, some arboreal, and others are lovers of the thickets. They migrate by night. ee constitute nearly their entire food, and they are among our best riends. 1 Reed and Chapman. LAND BIRDS 305 The black-masked Maryland yellow throat is one of the tiny warblers often seen in the Mississippi Valley. He haunts the thicket. His song, “witchery, witchery, witchery,” is characteristic of his active, nervous energy. The little black and white warbler, often called the black and white creeper, is about 5 inches long. It is a more active climber than even the true creepers, hanging from the under surface of branches and twigs or flitting from tree to tree. It is usually silent. Its occasional ‘“ see-see-see ”’ is thin and wiry. The wrens, thrashers, and the mocking-bird (Fig. 250) (Troglodyt'ide) include many fine singers. They are inconspicuously colored birds, feed- ing near the ground. Many of them like the low scrubby tangled growth so dear to the catbird, which cheers us all the summer day, rain or shine. This bird does valiant service as a caterpillar hunter, especially when feeding the young. | * LCMV FB Ze NA HA YY, ZAG AG, cD Y, is Dee SLi Wy z Fig. 250.—Mocking-bird. (Biological Survey, U. 8. Dept. Agricul.) The creepers (Certhi’ide) do good work in keeping down the pests of the tree trunks all the year around. The nuthatches (Par’id@) also help in tree keeping, as do our little chick- adees, which stay the winter through. The thrushes (Tur’dide@) are usually fine singers. The best known are the much-loved robin and bluebird (Fig. 251). There are several other families of Passeres, but lack of space forbids us to dwell longer on this fascinating subject. Economic Importance.—Millions of dollars’ worth of farm products are destroyed annually by insect pests, but if these great hordes of marauders were not held in check by their natural enemies, the birds, the devastation would be so great in a few years as to cause actual famine. 20 306 BRANCH CHORDATA -~+ Where man has not interfered, nature has a well-balanced arrangement for the protection of his crops. The grasses and low-growing herbs are protected from such enemies as the cut- worm, caterpillar, and grasshopper by the chipping sparrow, robin, and bluebird, and, farther afield, by the quail, meadow- lark, blackbird, and field sparrow. In the edge of the woods are Fig. 251.—Bluebird at edge of nest with grasshopper in mouth. (From photograph by Rey. P. B. Peabody.) (Bulletin 17, Biological Survey, U.S. Dept. of Agriculture.) the chewinks and brown thrashers; and in the deep woods, the ruffed grouse; while along the fresh-water streams and ponds may be seen the woodeocks, sandpipers, and snipes. In the trees “the woodpeckers, assisted by the nuthatches and creepers, look after insects on and beneath the bark of both the trunk and the branches.’! The chickadees, bluebirds, thrushes, warblers, 1 Weed and Dearborn, “‘ Birds in Their Relation to Man.” LAND BIRDS 307 vireos, kinglets, and many more guard the leaves. The insects of the air are preyed upon in the daytime by the diurnal birds, such as the swallows, swifts, kingbirds, and fly-catchers. Cre- puscular insects are caught by such birds as the whip-poor- will, night-hawk, and small owls. Hawks and owls destroy many rats and mice and other young rodents, while the vultures are very useful as scavangers, since they subsist largely on carrion. The South African secretary bird (Fig. 252) belongs in the list of friends.