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SYNOPSIS OF THE ANIMAL KINGDOM,

TOGETHER WITH A

LABORATORY PRACTICUM

OF

INVERTEBRATE ZOOLOGY.

BY HARRIS H. WILDER.

Privately printed for the use of students in Smith College.

Rorthampton, Wass. :
The Gazette Printing Company,
1894.
S

To my students in 95 and ’96, in acknowl-
edgement of the patient work with which
they have aided me in the completion of
this book.

Copyrighted by Harris H. Wilder, 1894.

106

GON TE Noles:

SYNOPSIS.
SYNOPSIS OF TYPES, ’ 3
DEFINITIONS OF TYPES, : :

SYNOPSIS AND DEFINITIONS OF CLASSES AND ORDERS,

PHYLOGENETIC DIAGRAM,

LABORATORY PRACTICUM.
PROTOZOA,
ASCON SPONGE,
SYCON SPONGE,
HypRa,
CAMPANULARIA,
TURBELLARIA,
DisToMUM,
TAENIA,
ROTIFERA
ASCARIS,
LUMBRICUS,
CAMBARUS,
PORCELLIO,
CYCLOPS,
SIMOCEPHALUS,
CYPRIS,

SPIDER,
CHILOPOD,
CALOPTENUS,
Mya,

HELIX,
BuGuULA,
ASTERIAS,

SEA URCHIN, :
BALANOGLOSSUS,

Poon Neo TS.

SV OR obs eO lei viakS:

AS EROTOZOA:

B. METAZOA.
DIVISION I. PROTAXONIA (Coelenterata).
TYPE I. PORIFERA.
Type II. CNIDARIA.
Type III. CTENOPHORA.
DIVISION Il. HETERAXONIA (Coelomata).
Type IV. ZYGONEURA.
SUB-TYPE I. PROTONEPHRIDOZOA (Scolecida).
Cladus) 1. Platodes:
Cladus Il.) Vermes:
Sup-TYPE Il. Me&rtTaANEPHRIDOZOA (Aposcolecida).
Cladus I. Articulata.
Sub-cladus I. Annelida.
Sub-cladus II. Arthropoda.
Cladus II. Mollusca.
Cladus III. Molluscoidea.
TYPE V. AMBULACRALIA.
Cladus. Echinodermata.
TYPE VI. CHORDATA.
Cladus I. Hemichorda.
Cladus II. Urochorda (Twunicata).
Cladus III. Cephalochorda (Leptocardit).
Cladus IV. Vertebrata.

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DET INTTIONS: OF TYRES:

A; PROTOZOA.

Unicellular animal organisms. Reproduction by fission and gemmation,
also by conjugation, which may simulate sex-differentiation. Colonial forms
may show polymorphism (with division of labor) and thus serve as transition-
forms between PROTOZOA and METAZOA.

B. METAZOA.

Multicellular animal organisms with sex-differentiation. The individual
begins as a single cell, formed by the union of two half cells (egg and sper-
matozoén) produced by the parents.

During development all metazoa pass through a blastula and gastrula stage,
supposed repetitions of ancient blastaea and gastraea forms.

DIVISION I. PROTAXONIA (Coelenterata).

‘*Gastraea animals,” i. e. forms with persisting gastraea characteristics,
the primary axis, the protostoma and the gastrocoele, from which all the cay-
ities of the body may be derived. No coelom.

TYPE I. PORIFERA.

Gastraea animals, sessile by the protostoma. Secondary excurrent opening,
osculum, at the apical pole: with numerous lateral pores in the body wall.
Middle layer (mesenchyma) present, derived from the primary endoderm. In
this are produced spicules, and the germ cells.

Type II. CNIDARIA.

Gastraea-animals, mostly marine, free-swimming or sessile at the aboral
pole. Develop tentacles around the protostoma. Certain specialized ecto-
derm cells form Cnidoblasts (nettle cells). These are most numerous on the
tentacles and serve as weapons. Middle layer a supporting lamella, seldom
cellular. Germ cells from ectoderm or endoderm,

10 INVERTEBRATE ZOOLOGY.

Type III. CTENOPHORA.

Gastraea animals, all marine ; structure a modified radiate, or doubly bi-
lateral one. Free-swimming; moving by means of eight meridional rows of
peculiar organs derived from cilia. Sense organs at apical pole. Adhesive
cells with spiral, contractile thread developed in ectoderm, replacing the Cni-
doblasts of Type II. Middle layer a richly developed gelatinous tissue filled
with muscle cells. Germ cells probably from ectoderm (at present a matter
of controversy).

{In comparing the three groups of Gastraea-animals, Types I-III, notice the differences
in development and use of the apical pole. In Lit serves as an excurrent orifice ; in II as

point of support, and in II] it is directed forward during locomotion and develops sense-
organs. ]

DIVISION Il. HETERAXONIA (Coelomata).

Bilateral animals, primary axis either embryonic or suppressed. Secondary
(middle) layer from two sources ; (1) from paired epithelial sacks (mesoderm);
(2) from wandering cells, derived from the primary endoderm (—mesenchyma).
The first is a new formation and is often reduced to single cells, or otherwise
obscurely indicated in the lower forms. The second is probably homologous
with the middle layer of the Protaxonia. Coelom present, either a proto-
coelom (derivative of Blastocoele) or metacoelom (cavities of the mesodermic
sacks).

Type IV. ZYGONEURA.

Animals derived from the hypothetical Trochozoén (or an earlier form, Pro-
trochozoén) which are frequently repeated throughout the class in the
‘** Trochophore-larva” and similar forms. Nervous system consists of an api-
cal cerebral ganglion from which proceeds at least one pair of longitudinal
nerves.

SUB-TYPE I. PROTONEPHRIDOZOA (Scolecida).

Entire body a ‘‘ prosoma” (i. e. derived from the ancestral form), main body
cavity the protocoelom. Metacoelom represented as protonephridium and pri-
mary sack-gonads.

Cladus I. Platodes.

Forms derived from the Protrochozoén, which is represented in a few mem-
bers of the group by a “ protrochula” larva. The adult forms are flat, either
creeping or swimming slowly by means of cilia, or reduced by parasitic life,

INVERTEBRATE ZOOLOGY. il

Intestine incomplete and without anal orifice. Protocoelom secondarily filled
up by a connective tissue parenchyma, derived from the mesenchyma. Pro-
tonephridium a system of branching tubules, the so-called ‘‘ water-vascular
system.” Mostly hermaphroditic with complicated reproductive system.

Cladus II. Vermes.

Forms derived from Trochozoén. Protocoelom serves as body cavity and is
not filled with mesenchyma. Intestine complete with anus. The animals of
this class are externally very unlike and fitted for many different environ-
ments. Some are plainly modified Trochophores when adult, others pass this
stage in early life, while in others the stage has dropped out. They are most
easily distinguished from other worm-like forms by their lack of segmentation.

SuB-TYPE II. METANEPHRIDOZOA (Aposcolecida).

Anterior part of body alone (Prosoma) derived from Trochozoén, to which
the remainder (—Metasoma, generally the larger portion) is added by success-
ive growths forming segments or somites. Each somite forms organs like the
prosoma, which are distinguished as meta-nephridia, and secondary gonads.
In some forms the organs of the prosoma remain to supply that portion, in
others they early disappear, the region being secondarily supplied by in-
growths from the metasomatic organs. The body-cavity is the meta-coelom,
formed by paired mesodermic coelom sacks, which may be considered as ex-
pansions of the sack gonads in which the germ cells are localized in certain
areas as ‘‘surface gonads.” The metanephridia communicate internally with
the coelom and externally with the outside. They may be repetitions or seg-
mentations of the protonephridia, secondarily connected with the coelom ; or
they may be evaginations of the coelom itself.

Cladus IT. Articulata:

Segmentation very pronounced, each segment typically furnished with a
pair of appendages, jointed in the higher forms. Segments and appendages
often show marked specialization in different body regions. Integument pro-
tected by a cuticula which may become a thick chitinous exoskeleton. Meta-
coelom spacious, mesenchyma poorly developed; nervous system a double
cerebral ganglion dorsal to intestine, connected by commissures to a ventral
ganglionic chain. Metanephridia in the typical form segmentally arranged,
in higher forms modified or fail, being replaced by other organs,

12 INVERTEBRATE ZOOLOGY.

Sub-cladus I. Annelida.

Appendages in the form of parapodia, i. e. fleshy outgrowths of the lateral
walls, bearing bristles, gills, and other organs, but never jointed. In some
forms the processes are suppressed, the bristles being inserted in pits. No
marked differentiation of the body into definite body regions.

In this group appear the most typical Trochophore larvae.

Sub-cladus II. Arthropoda.

Appendages jointed. A Trochophore larva does not appear, but their posi-
tion is determined by means of their marked relationship to the Annelids.
Development by larval forms is common, but many of these are plainly sec-
ondarily acquired and of no value in phylogenesis.

Cladus II. Mollusca.

Metasoma consisting of one segment, which early fuses with the prosoma,
resulting in an apparently unsegmented body. Metanephridia a single pair.
Metacoelom almost filled with parenchymatous tissue, the pericardial cavity
and those of the germ glands alone remaining. The body consists typically
of head, foot and visceral sack, of which the first two may fail or be modified
beyond recognition. The body is generally surrounded by a duplicature of
the integument termed the mantle, which secretes a calcareous shell and en-
closes a branchial cavity. As reminiscence of the Trochozoén, there fre-
quently appears the ‘‘ Veliger” larva, similar to the Trochophore.

Cladus III. Molluscoidea.

Sessile animals, mostly marine and often colonial, either enclosed in cells or
protected by dorsal and ventral calcareous shells. Mouth surrounded by a
ridge, the lophophore, which bears ciliated tentacles, or two spiral ciliated
arms. Intestine U-shaped, with anus just outside the lophophore. Meta-
coelom present, developing in the typical forms from a pair of lateral sacs.
One pair of metanephridia. Central nervous system a ganglion between
mouth and anus. The apparent lack of segmentation may be explained here
as in Mollusca. by supposing a simple metasoma

INVERTEBRATE ZOOLOGY. 13
Type V. AMBULACRALIA (with one Cladus).

Cladus. Echinodermata.

Primarily bilateral pelagic forms, which attain a secondary radiate penta-
merous structure, after which they may become creeping or even sessile. The
bilateral larvae are all derivable from a common form, the Pro-awricularia,
which is itself derived directly from the gastraea by the formation of a sec-
ondary mouth and the conversion of the protostoma into the anus. This form
somewhat resembles the trochozoén, but differs from it in the origin of mouth
and anus, and in the absence of an apical sense organ.

During development the protocoelom becomes filled with mesenchyma, and
the definite coelom appears in the form of a pair of mesodermic sacs (or one
double sac), the enterocoeles, from which arise typically a pair of secondary
sacs, assuming the form of five-pointed rosettes, the ydrocoeles. Of these,
the right one aborts and the left one grows into the water-vascular system of
the definite radiate form. In most cases the right hydrocoele is entirely sup-
pressed. The adult form possesses oral and ab-oral surfaces, which corres-
pond respectively to the left and right sides of the posterior portion of the larva.

Larval locomotion is by cilia, the adult mainly by the water-vascular sys-
tem. Characteristic in all stages is the possession of a skeleton, composed of
calcareous elements, which may form closely articulated plates, a network of
loosely woven spicules, or may be reduced to minute granules imbedded in the
integument.

[P. and L. SARASIN and others attribute to the hydrocoeles the value of nephridia, and
Bury claims that the enterocoele normally develops from two pairs of coelom-sacs.]

TYPE VI. CHORDATA.

Bilateral animals with dorsal nervous system, supported ventrally during
some stage at least by a skeletal rod, the notochord, derived from the endo-
derm. The pharynx is perforated by lateral slits, respiratory in function,
which may develop gills, supported by skeletal rods, the visceral or gill arches.
The protostoma is embryonic and occupies the future dorsal region, appearing
in higher embryoes as an elongated groove or cleft, the primitive streak. The
mesoderm arises from the lateral region of the primordial intestine, typically
in the form of paired sacs, segmentally arranged, but in modified forms as
more or less solid masses, which segment and develop cavities after separation
from the endoderm. From these mesodermic cavities the metacoelom is
formed. The protocoelom becomes filled with mesenchyma, which forms the
connective tissues and the blood vessels.

14 INVERTEBRATE ZOOLOGY.

Cladus I. Hemichorda.

Notochord confined to anterior part of body above pharynx. Nervous sys-
tem dorsal and ventral chords, not entirely distinct from ectoderm. Pharynx
perforated by paired gill slits. Genital organs consist of several pairs of
sac-gonads. opening independently on the dorsal side. As diverticula of the
primordial intestine (archenteron) arise 2-8 pairs of coelom-sacs, as well as a
median dorsal pore, compared by some to the dorsal pore of Echinoderm lar-
vae. This appears double in some species. Some species develop directly,
others by a free-swimming larva, the Tornaria, which appears in some re-
spects similar to Proauricularia, and in others to the trochophore. Develop-
ment by Tornaria-larva, is undoubtedly more primitive than the direct method,
and hence Tornaria must represent the free-swimming pelagic ancestor of the
Chordata. Its relationship to the other primitive forms is uncertain.

Cladus II. Urochorda (Tunicata).

A group of marine Chordata, representing various stages of degeneracy,
and thus of very varied external appearance. The larvae are free-swimming
and pelagic, but may become sessile in adult life. The notochord is confined
to the caudal region where it supports the posterior part of the dorsal nervous
system. It is persistant throughout life in a single group of small pelagic
forms, the Perennichordata (Appendicularia), becoming reduced in all others.
Corresponding to the changes in the notochord, the larval nervous system is
elongated, but in the adult becomes reduced to a single ganglion, lying dorsal
to the pharynx. The mesoderm arises as in typical chordata, but is without
trace of segmentation, and lacks the coelomic cavities, which either do not
appear or become early obliterated. Nephridia fail. The body of the adult
is enclosed in a mantle or tunic, which may be gelatinous, leathery or carti-
laginous, and posesses two orifices ; an incurrent or oral, and an excurrent or
cloacal. The pharynx is perforated by gill slits which may appear in two
lateral rows, or by secondary reduplication may convert the entire pharyngeal
wall into a lattice-work. The water passes from these slits into a peri-
branchial or cloacal cavity, formed by the mantle, and into which the intes-
tine and the genital ducts also open. In the sessile forms the intestine is
U-shaped, and the two mantle openings approximate, while in the free-swim-
ming forms they are situated at the two poles of the oval or cask-shaped body.
Asexual reproduction combined with complicated alternation of generations
occur in this group, The sexual forms are hermaphroditic,

INVERTEBRATE ZOOLOGY. 15

Cladus III. Cephalochorda.

Elongated fish-like marine forms, without head, brain, or skull. Notochord
persistant, extending through entire body from tip to tip. Mouth near ante-
rior end. Pharynx perforated by paired gill slits, which open, not to the ex-
terior, butinto a space formed by integumental folds, the peri-branchial cav-
ity. This communicates with the exterior through a median opening, anterior
to the arms, the atriopore.

The nervous system consists of a dorsal cord lying upon the notochord. It
possesses a central lumen which enlarges a little at the anterior end. The
sense organs are a set of cilia about the mouth, a median olfactory pit and a
median pigment-fleck lying upon the anterior end of the nerve cord.

The reproductive glands are a series of pairs of follicles projecting into the
peri-branchial cavity. The germ cells become free by rupture of the follicu-
lar walls, and later pass into the water through the mouth or the atriopore.
The excretory organs consist of paired nephridia in the branchial region,
which pass from the true coelom into the peri-branchial cavity.

Cladus IV. Vertebrata.

The main group of Chordata, characterized by the possession of a head and
two pairs of lateral fins, which may become modified in various ways. The
anterior portion of the central nervous system becomes enlarged to form a
brain, which consists of five vesicles, and bears three pairs of sense-capsules,
nose, eye and ear.

The notochord, which ends anteriorly at about the level of the ear-capsules,
is cartilaginous, in some stage at least, but in the higher forms is reinforced
by segmentally arranged osseous arches and other elements alternating with
the mesodermic somites, which may entirely replace the original structure
(vertebral column.) The brain and sense capsules are protected by a cranium,
which consists primarily of two pairs of cartilaginous elements, to which may
be added osseous tissues. Visceral arches always appear, but in the higher
terrestrial forms, only show their primitive relationship in larval or embryonic
life, and later undergo modification and reduction. The germ-glands are
surface-gonads, i. e. localized portions of the coelomic mesoderm.

The excretory organs develop as paired nephridia, appearing in several
series ; these are consolidated to form kidneys, or utilized to convey the germ-
cells,

16 INVERTEBRATE ZOOLOGY.

Sub-cladus I. Cyclostomata.

Mouth circular, suctorial, without true jaws. Within the mouth are
‘*teeth” of pure epidermic formation, and not homologous with the teeth of
higher vertebrates. Paired limbs fail. The gill arches connect with each
other and form a sort of basket-work in the pharyngeal region.

Sub-cladus II. Gnathostomata.

Mouth slit-like, transverse, furnished with jaws, which are originally modi-
fications of the first visceral arch. The integument develops horny plates,
formed from both epidermis and cutis, some of which become localized on
the jaws as true teeth, others by fusion giving rise to the so-called ‘‘ dermal ”
bones, which reinforce the skeleton. Paired limbs typically present. Appen-
dicular skeleton develops, consisting of girdles about the body with which the
skeleton of the free-limbs articulates.

Synopsis and Definitions of the Classes and Orders.

A; PROTOZOA:

Classe SS RoIZORODAC EE eee ee eee

Order 1.

iPropoplasta sesh caer

Sub-order 1. Protoplasta lobosa..

Sub-order 2. Protoplasta filosa. .

Order 2.

Order 38.

Order 4.

ehOZORME eee eee

IRRVOIOIRTHIEY 65 nodos Sout ac

Foraminifera .

Protozoa without a cell wall, moving by
pseudopodia.

.Fresh water rhizopods found crawling

over submerged objects, and on damp
bog-moss, either naked or enclosed by a
shell made of chitinous plates, sand
grains, etc., with one large opening, out
of which the animal extends its pseudo-
podia.

With thick, generally rounded pseudo-
podia. 4 Amoeba, Difflugia,

With fine, thread-like pseudopodia.
% Englypha.

.Free-swimming fresh water Rhizopods,

radiate in structure and often possessing
a silicious skeleton, but without central
capsule. 4 Actinophrys, Clathrulina.

Marine Rhizopods, with radiate, silicious
skeleton. Protoplasm divided by a cen-
tral capsule into extra- and infra-capsular
plasm. 4 Polycystina.

..Marine Rhizopods, with calcareous shell,

perforated with very numerous minute
openings (foramina) through which the
animal projects its fine pseudopodia.

* Globigerina, etc., im deep-sea dredg-
ings.

(18)

INVERTEBRATE ZOOLOGY. 19

Class hiner IN EUSORTA c.icm ence ie cle: Protozoa with cell-wall, moving by cilia
or flagella.
Order 1. Ciliata........ Saree wrntscete Infusoria moving by cilia.
Sub-order 1. Holotricha. .. ...Cilia uniformly covering the body.
*% Paramoecium.
Sub-order 2. Heterotrichu..... Cilia in patches and often of different
lengths. ye Stentor.
Sub-order 3. Hypotricha....... Cilia only underneath. Creeping forms.
Sub-order 4. Peritricha........ Cilia in a ring around the mouth.
* Vorticella, Epistylis.
Order 2. Flagellata....... ......Infusoria moving by flagella.

Sub-order 1. Nudoflagellata....Simple monads. ye Englena.

Sub-order 2. Choanoflagellata. .Collared monads, often colonial.
*% Codosiga.

Sub-order 8. Cilioflagellata. ...Mostly marine forms with a silicious exo-
skeleton. 4 Ceratium.

Sub-order 4. Cystoflagellata...Very large marine forms, with reticula-
ted endoplasm. 4 Noctiluca.

Supplementary Sub-order 5. Volvocina..... Spherical colonies, showing
division of labor. Perhaps similar to
Blastaea. y& Volvow.

Order 3. Suctoria ...... ........With knobbed tentacular processes that

act as suckers.

SUPPLEMENTARY CLASSES.

@lassee GREGARINIDA 220.0. ole Worm-like unicellular parasites, with
contractile layer. Reproduction by
means of pseudonavicella-cyst.

*% Monocystis.

Class. SCHIZOMYCETES (Bacteria)...The most minute of organisms. The
cause of ferment, decomposition and dis-
ease, now generally placed among the
plants. The chief forms are the ball
form, Micrococcus, the sticks and threads,
Bacterium and Bacillus, and the spiral
form, Spirillum.

20

INVERTEBRATE ZOOLOGY.

B. M

Division I.

Type I. PORIFERA.

Class I. CALCISPONGIAE...........

Order 1.

Order 2.

Order 3.

Class II.

Class III.

Type II.

IASCONIGa Se ae eee oe

SVCOMIdAaee eer mer ect

WMeuconidaneesise cee

SIMIGISPONGIAE. «2... - 5+.

KERATOSPONGIAE.....

CNIDARIA (Coelenterata).

MARS IL, TEDMDIRNOAONS 465 su Sesuae coc

Order 1.

ANWHNIYCHBIES & gsos soa500

ETAZOA.
PROTAXONIA.

.Spicules calcareous—structure of sponge

comparatively simple.

Wall of sponge not folded—main cavity
lined with digestive cells. 4 Ascetta.

Wall of sponge forming oblong chambers
opening directly into the main cavity.
Digestive cells confined to the chambers.
*% Sycandra.

.Wall of sponge with a very thick meso-

derm, in which are spherical chambers
lined with digestive endodermal cells
Chambers connected with the exterior
and with the main internal cavity by
branching canals.

Spicules silicious, sometimes woven to-
gether like threads.
% Huplectella, Spongilla.

..No spicules, skeleton a mesh-work of

woven threads, or wanting.
*% Euspongia.

Polyp form [HypRULA] without mesente-
ries, only in a few instances producing
coral. Medusa form (Craspedota) gener-
ally small, with velum, 4-8 radiating ca-
nals, uncovered sense organs, generally a
long manubrium and no genital pouches.
Marginal lobes wanting. Gelatinous mid-
dle layer without cells.

Sexual cells produced by polyp-form.

No medusa generation (free or reduced).

INVERTEBRATE ZOOLOGY. 21

Sub-order 1. Hydrida..........Simple, fresh-water polyps. Solitary in-
dividuals reproducing asexually in sum-
mer and sexually at the approach of win-
ter. Do not form colonies. 4 Hydra.

Sub-order 2. Hydrocorallinae...Tropical marine forms, polymorphic, in
colonies, producing a sort of coral.
* Millipora.

Order 2. Hydro-medusae.........Sexual cells produced by medusa, which
may be 1) a free form produced by a ses-
sile or floating colony of polyps: 2) a re-
duced form borne ona polyp colony ; 3)
a free-swimming form without polyp an-
cestors. All marine.

Sub-order 1. Gymnoblastea-anthomedusae .. Sessile colonies of polyps,
the separate individuals of which are
naked, and not protected by the perisarc.
The medusae possess ocelli and genital
organs in the manubrium. 4 Pennaria
with reduced medusae.

§ #&Syncoryne—polyp } fr

bee om one colony.
( Sarsia—=medusa 3

Sub-order 2. Calyptoblastea-leptomedusae. ...Sessile colonies of polyps,
perisarc forming cups for the protection
of the individuals. Medusae with oto-
cysts and genital organs on radial canals.
* Campanularia with free medusa.

* Sertularia with reduced medusa.

«

Sub-order 3. Trachymedusae...Free-swimming medusa with direct de-
velopment (no polyps). Velum, 4-6 ra-
diating canals, and other characteristics
of. hydro-medusae. Evidently forms
with suppressed polyp generation. {Prim-
itive forms that have not developed the
polyp form—BRoOokSs. |
* Geryonia, Liriope.

22 INVERTEBRATE ZOOLOGY.

Sub-order 4. Siphonophora. ...Free-swimming colonies of polymorphic
individuals representing both types (polyp
and medusa) and characterized by the
occurrence of a complex of several per-
sons, known as a Cormidium. In some
forms the medusae become free, > Vel-
lela; in the majority the medusae are
reduced, and develop germ cells (gener-
ally one egg in female) in the manubrium.
*% Physophora, Physalia.

Class) Il.) “SCYPHOZOAs2 scccigs. kre Polyp form [ScyPHULA] with an invagi-
nated protostoma, forming oesophagus
and secondary mouth, mesenteries pres-
ent, extending between oesophagus and
body-wall. Gastrocoele containing mes-
enterial filaments. Medusa form (acras-
peda) large, without velum, with very
many branching radiating canals, with
square mouth and four genital pouches,
with marginal lobes on sub-umbrellar
side. Body cavity containing gastral fil-
aments. Gelatinous middle layer cellu-
lar.

Order Ie Anthozoas sae a eee Polyps of Scyphula type, without medusa
generation. Mostly coral producers.

Sub-order 1. Hexacoralla......Mesenteries and other parts in sixes.
Many forms produce coral, showing the
arrangement of the mesenteries.

* Metridium, Fungia.

Sub-order 2. Octocoralla (Aleyonaria) ........ Mesenteries and tentacles
eight —coral consists of a horny axis
coated with a polyparium containing
sklerites. ye Renilla, Corallium.

Sub-order 8. Tetracoralla......Partsin fours. All fossil. (Palaeozoic.)
Order 2. Scyphomedusae....... Large medusae of the above description

(under Scyphozoa), which alternate with
reduced polyp generation of the Scyphula
type. 4 Aurelia.

INVERTEBRATE ZOOLOGY. 23

Supplementary Class. PLANULOIDEA....Minute endoparasites without mouth

Type ILI.

@lassmles UDENTACULATAY mdse cee.

Class IT.

Type IV.

Sub-type I.
Cladus I.
Class I.. TURBELLARIA

Order 1.

Order 2.

Sub-order 1. Triclada........

Sub-order 2. Polyclada.......

Class IL.

NuDA....

CTENOPHORA.

Division II.

ZYGONEURA.

Platodes.

Rhabdocoela...........

Dendrocoela........

PRR MATODHSsa aces eae

or intestinal lumen, resembling the pla-
nula larva of Cnidarian polyps. There
are two groups: the Dicyemidae, found
in the nephridia of Cephalopods, and the
Orthonectidae, in Ophiuridea, Turbellaria
and Nemertea. They have been™consid-
ered as Mesozoa, between Protozoa and
Metazoa, but are more probably Cnidaria,
reduced by parasitism.

With two long, prehensile, thread-like
tentacles. 4 Pleurobrachia.

.. Tentacles wanting. 4 Beroe.

HETERAXONIA.

PROTONEPHRIDOZOA (Scolecida).

Small, free-swimming Platodes, of oval
shape ; body very contractile and covered
with cilia.

-Intestine a straight, unbranched tube.

Pharynx simple: small forms.
% Mesostomum.

..Intestine dendritic. Pharynx tubular.

Larger forms, very flat.

.. Intestine with three main trunks—one

anterior, and two posterior. ye Planaria.

. Intestine like foregoing, but with more

than two posterior branches.
%& Planocera.

.Parasitic Platodes. Body of adult not

ciliated, but generally furnished with
sucking-discs. Intestine much as in
Triclada.

24 INVERTEBRATE ZOOLOGY.

Order 1. Monogenea (Polystomeae)....Ecto-parasites upon gills, integu-
ment, bladder, etc., of aquatic verte-
brates. Sucking-discs, three or more.
Development direct. 4 Polystomum.

Order 2. Digenea (Distomeae)....Ento-parasites with never more than
two sucking-discs. Development by het-
erogony, through forms known as Sporo-
cyst, Redia, Cercaria, etc., which inhabit
several hosts, the first being a pond snail,
or some allied form.

%*% Phasciola, (Distomum).

Class III. CrSTopES......-. ........Ento-parasitic Platodes without intestine.
Adult form generally composed of ‘‘links”
(Proglottids), which may be considered
reduplicated abdomens, or as attaining
the value of individuals of a colony.
Larval form (Cysticercus) provided with
sucking-discs, and often loops. In the
typical forms the cysticercus encysts it-
self in the muscles or internal organs of
its first host, and develops into the chain-
form only when swallowed by some spe-
cial animal, which thus serves as its sec-
ond host. + Taenia.

Cladus II. Vermes,

Class I. ROTIFERA....... ........-Minute aquatic forms, which may be
considered as modified Trochozoa. The
prae-oral band of cilia persists, often
modified to form a pair of contractile
organs resembling rotating wheels. Pro-
tocoelom spacious. Alimentary canal
differentiated into a stomach, containing
chitinous teeth, an intestine and a cloaca
into which the protonephridia and repro-
ductive ducts empty. Generally a jointed
forked appendage or ‘‘ foot,” projecting
posteriorily and serving for temporary
attachment. Bisexual, the males rare,
and much reduced.

* Brachionus, Rotifer.

Class II.

Class III.

Class IV.

INVERTEBRATE ZOOLOGY. 25

GASTROTRECHIA wees chore

HW NDORROCTAGR ce aeen nie

INE MATODESS-ysiccc siete sites

Minute aquatic forms about the size of
large Infusoria, having an independent
origin from Trochozoa and modified in a
different manner from the above. They
are elongated, somewhat flattened, and
possess a double band of cilia on the ven-
tral side, derived from the ventral stripe
of the Trochozoén. Ciliated zones fail,
body generally terminated in a fork.

*& Ichthidium.

Aquatic forms, mostly marine—probably
to be viewed as Trochozoa, modified by
sessile life. The larvae are free swim-
ming, but soon become attached by a
stalk developed from the apical pole.
The prae-oral zone (Trochus) develops
into a crown of ciliated tentacles, within
which are mouth and anus, as well as
the genital and nephridial openings. The
apical ganglion of the larva disappears
and is functionally replaced by another,
situated between mouth and anus. The
group is generally referred to Bryozoa,
q. Vv. ¥%& Urnatella, Loxosoma.

.Long, cylindrical worms without cilia.

Body cavity present. Sub-cuticula with
four longitudinal thickenings, dorsal, ven-
tral and lateral, between which lie four
bands of longitudinal muscles. Proto-
nephridia forming two lateral canals en-
‘sased in the lateral sub-cuticular thick-
enings. Sack gonads long and tubular,
often contorted. Ventral nervous system
an oesophageal ring, from which issue
longitudinal nerves, of which two (dor-
sal and ventral) lie in the sub-cuticular
ridges. Bisexual with a single exception.
Development direct. Free-swimming and

26 INVERTEBRATE ZOOLOGY.

parasitic forms. ¥ Trichina, Anguillula
(vinegar-eel). Ascaris (pin-worm). Gor-
dius (hair-snake).

Class V. ACANTHOCEPHALI.... ...A single family of worms, externally
similar to last, but with an anterior ex-
tensile proboscis beset with hooks, and
no intestinal canal. The body wall de-
velops two solid masses (Lemnisci) which
project into the protocoelom. The re-
productive organs open posteriorly. De-
velopment by metamorphosis. Larval
stage in crustaceans and insects, adult in
intestine of vertebrates.

* Echinorhynchus.

SUPPLEMENTARY CLASS—NEMERTINI.

Flattened forms, often very long, externally covered with cilia. At ante-
rior end a long retractile proboscis. Protocoelom filled with parenchyma.
Alimentary canal complete with anal orifice. Nephridia and gonads repeated
in pairs along the body. Complicated blood and nervous systems. Bisexual.
Many develop by metamorphosis and possess a curious larval form, the
‘* Pilidium,” which is similar to a Protrochula.

The relations of this group are very uncertain. Many characteristics would
place them near the Platodes, but the complete alimentary canal, the blood
system and the segmentally arranged nephridia and gonads would exclude
them from these and place them nearer the Annelides. It seems at present
more probable that they are Protonephridozoa, and that the metameric char-
acter of some of the internal organs is due to a reduplication of protosomatic
elements, rather than to the formation of a metasoma (cf. the reduplication of
the abdomen in Taenia).

Order 1. Hoplonemertini........ Proboscis armed with bristles.

Order 2. Schizonemertini........ Proboscis unarmed, head nearly divided
by deep, longitudinal fissures.

Order 3, Palaeonemertini........Proboscis unarmed. Head nearly entire.

INVERTEBRATE ZOOLOGY. 27

Sub-type II. MertTaNnepHriIpozoa (Aposcolecida).
Cladus III. Articulata.
Sub-cladus I. Annelida.

Class I. ARCHIANNELIDES..........Small marine forms of very simple or-
ganization. No external segmentation.
Metameres all alike; bristles, cilia and
parapodia fail. Development with a
metomorphosis, in which occurs the most
typical trochophore. Polygordius.

Class Ul.” CHARTOPODA: ....<% vs. se: Typical Annelids, with well marked ex-
ternal segments, corresponding to the in-
ternal metamerism—segments furnished
with paired groups of chitinous bristles.

Order 1. Polychaeta...... .... .Bristles conspicuous, situated on raised
lAteral portions, parapodia. Head gen-
erally present. Development by a meta-
morphosis, usually with a Trochophore

larva.
Sub-order 1. P. errantia....... Free-swimming, active, predaceous.
* Nereis.
Sub-order 2. P. sedentaria.....Live in tubes built of sand, mud, bits of

shell, etc., subsist upon vegetable sub-
stances. ye Amphitrite, Serpula.

Order 2. Oligochaeta............ Bristles very small, sunk in hollows along
the sides ; no parapodia ; no distinct head;
hermaphroditic, development direct.

Sub-order 1. O. limicola....... Aquatic, in mud of swamps. » Nais.
Sub-order 2. O. terricola....... In damp earth. 4 Lumbricus.
@lasselliee EMRUDINHAY 22... y55.2- -Aquatic hermaphroditic ecto-parasites ;

segments without bristles ; move by ter-
minal, adhesive suckers. External and
internal segments do not correspond.

Order 1. Rhynchobdellidae...... Pharynx extensile, forming a sort of pro-
boscis. ye Clepsine.

28 INVERTEBRATE ZOOLOGY.

Order 2. Gnathobdellidae........Pharynx not extensile, with three longi-
tudinal ridges which are often toothed.
* Hirudo.

SUPPLEMENTARY CLASSES.

Class CHAETIFERA, formerly taken with Sipunculoidea to form class Gephy-
rea. Here belong a very few marine worms, Echiurus, Bonellia, etc., which
show affinities to the Chaetopoda. .They are segmented only as larvae, but
possess paired nephridia and a system of blood vessels similar to that of
Annelids.

Class SIPUNCULOIDEA includes a very few forms of marine worms, bearing
some slight affinity to Annelids. They were formerly united with Chaetifera
to form the class Gephyrea. They are cylindrical, unsegmented forms with-
out bristles, and possess a retractile proboscis. 4 Sipuneulus, Phascolosoma.

Class CHAETOGNATHA. This includes one form, Sagitta, a small, transpar-
ent, unsegmented worm found on the surface of the ocean. The body is flat
and possesses lateral fire-like extensions. The mouth is armed with jaws beset
with sharp hooks. Hermaphroditic. It develops lateral coelom sacks, which
appear to have the value of a metacoelom. It is placed by some with the
Nematodes.

Sub-cladus II. Arthropoda.

Class I. CRUSTACEA................Aquatic Arthropoda, a few being second-
arily adapted to a terrestrial life. Res-
piration either through the general sur-
face of the integument or by localized
thin portions of the same, in the form of
evaginated plates or structures, almost
always placed in some relation to the
appendages—and known as ‘‘ gills.” Ap-
pendages typically composed of two
branches, which may be modified beyond
recognition. Development from a Nau-
plias larva, which is suppressed in the
higher forms. Female generally pro-
vided with a brood-sack for the care of
the young.

INVERTEBRATE ZOOLOGY. 29

Sub-class I. ENTOMOSTRAKA....... Small, often minute Crustacea with a
variable number of segments (not 20).
Abdomen generally without appendages.
Nauplias larva almost universal. Parthe-
nogenesis frequent.

Order 1. Branchiopoda... .......With flat, leaf-like legs bearing gill-sacks.
Body generally enclosed in an integu-
mental duplicature in the form of lat-
eral shells or a dorsal shield.

Sub-order 1. Phyllopoda....... Body plainly segmented. Numerous
pairs of legs (10-40). 4% Branchipus.

Sub-order 2. Cladocera........ Body enclosed in a shell with two lateral
valves—head free; second pair of ante-
meae enormously developed, and used as
oars. 4-6 pairs of legs. Gill-sacks may
fail. +e Daphnia.

Order 2. Copepoda...............Body generally elongated and plainly
segmented, without integumental dupli-
cature. 4-5 pairs of flattened, two-
branched legs used as oars. Eggs in two
lateral pedicelled sacks. Many forms re-
duced by parasitism.

Sub-order 1. Hucopepoda...... Free-swimming forms with typical char-
acteristics. ye Cyclops.

Sub-order 2. Copepoda parasitica... ..Parasites upon gills of fish or in
internalorgans. Often witha free-swim-
ming stage, especially in male. In later
life may be reduced to a shapeless sack.
Antennae may be modified to form
hooks. 4 Lernaea.

Sub-order 3. Branchiura.......Flattened oval forms, attached to the
sides of fish and subsisting upon slime.

* Argulus.
Oriler 3. Ostracoda: so... 55566: Body, including head, enclosed in a bi-

valve shell, with hinge and adductor
muscle. seven pairs of appendages, of
which only 2(or 8) may be reckoned as
legs. > Cypris.

30

Order 4. Cirripedia....

Sub-order 1. Lepadoidea.
Sub-order 2. Balanoidea......
Sub-order 3. Rhizocephala.. .

Sub-class II. MALACOSTRAKA

INVERTEBRATE ZOOLOGY.

Sessile forms, enclosed in an inverted
position in a calcareous 2-valved shell.
Generally six pairs of 2-branched legs,
modified to form attenuated many jointed
cirri. Larval stage a free-swimming
nauplias which soon becomes fixed by
the first antennae. This after passing
through a so-called ‘‘ Cypris” stage, de-
velops into the adult.

Forms with stalk and flexible valves—
skeleton mainly composed of scuta, terga
and carina. ye Lepas.

.Forms without stalk, skeleton reinforced

by lateral pieces, which, with carina and
rostrum, form a calcareous tube.
* Balanus.

.Degenerate parasites upon crabs (Bra-

chyura). Body consists of a sack, from
which grow countless root-like threads
(=the stalks, morphologically) which
penetrate the flesh of the host. Recog-
nizable as Cirripedia only in larval life.
% Succulina.

Generally large forms with a constant
number of segments (20) consisting of a
head with five, a thorax with eight and
an abdomen of seven segments. The first
two portions are often fused to form a
cephalo-thorax of thirteen segments.
Only the first six abdominal segments
bear appendages, and of these the last
pair is generally modified and united with
the terminal segment to form a caudal
appendage. The paired reproductive ori-
fices of the male are found upon the last
thoracic segment, and those of the female
upon the third from the last. Develop-
ment sometimes direct—generally with a
metamorphosis. Nauplias larvae appear
only in a few primitive forms.

INVERTEBRATE ZOOLOGY. 31

Legion 1. Phyllocarida (Leptostraka)....This group, mostly fossil, contains
but a single pelagic form, valuable as a
link between Entomostraka and Malakos-
traka. A smallintegumental duplicature
covers the head and thorax. The abdomen
is 8-jointed, thus departing from the con-
stant number found in Malacostraka.
The feet are like those of Phyllopods.

*% Nebalia.

Legion 2. Arthrostraka (Edriophthalmata)......Sessile-eyed Malacostraka,
with free thoracic segments, and without
carapace. Thoracic appendages distribu-
ted as one mavxilliped and seven legs.
Brood cavity borne between thoracic legs.

Order d= “Amphipoda. ..-. 5-3... Compressed forms, body generally bent
into a curve. Gills upon the thoracic
legs. Abdomen with six pairs of legs, of
which the first three are used in swim-
ming, and the last three form a springing
organ. In a few forms the abdomen is
reduced. +e Gammarus.

Ondere2se lsopoddaee a9. 55-45 Depressed forms with seven free thoracic
segments. The abdominal appendages
are in the form of flattened plates and
protect the gills. 4 Porcellio.

Legion 8. Thoracostraka (Podophthalmata)....Eyes situated upon movable
stalks. Carapace involving all or nearly
all the thoracic rings. Brood cavity upon
the ventral side of the flexible abdoinen
and protected by the sixth abdominal ap-
pendage and the terminal segment
(telson).

Ordern emt CUMAGCCA fat. cee. Carapace small, involving only 3-4 tho-
racic segments, two pairs of maxillipeds
and six pairs of legs. Abdomen of fe-
male without appendages; of male with
3-5. tc Diastylis.

32 INVERTEBRATE ZOOLOGY.

Order 2. -‘Stomatopoda:.....-..-.. Carapace involving five thoracic seg-
ments, five pairs of maxillipeds, and
three pairs of legs. Gills upon the ab-
dominal appendages. ye Squilla.

Order 35) Sehiz0poGaee eee ee Carapace involving entire thorax, eight
pairs of two-branched, gill-bearing, tho-
racic legs, no maxillipeds. 4 Mysis.

Order 4. “Dekapodane.--s- += a: Carapace large and heavy, involving the
entire thorax, six pairs of maxillipeds and
five pairs of legs, of which the first bears
aheavy claw. Gills at base of thoracic
feet upon the sides, protected by the edge
of the carapace.

Sub-order 1. Maecrura..........Abdomen elongated, bearing appendages.
*% Homarus.
Sub-order 2. Brachyura....... Carapace generally broader than long,

with grooves for the reception of the
short antennae and eyes. Abdomen re-
duced, and folded back over the sternum.
*% Cancer.

SUPPLEMENT TO THE CRUSTACEA.
TRILOBITEA.

An important group of fossil forms, presenting some superficial resemblance
to the Isopods. They are oval and flattened in form, and possess a dorsal car-
apace, divided by two longitudinal grooves into three areas, one median
(rhachis) and two lateral (plewrae). The carapace consists of a cephalo-
thorax, and a variable number of segments, of which the anterior ones are
free-moving, and termed the ‘‘ thorax,” followed by several fused ones, the
‘abdomen ” or pygidium.

The cephalo thorax consists of a central piece (glabellum), and two lateral
pieces, the fixed and movable cheeks, between which are a pair of compound
eyes.

INVERTEBRATE ZOOLOGY. 33

The ventral side is almost unknown. Probably each thoracic segment has
a pair of crustacean-like legs, above which there may have been a pair of
gills, protected by the overhanging edge of the carapace. Recently (1894)
some finely preserved specimens have been discovered showing one pair of
long antennae.

The Trilobites appear to have close affinity to the branchiate Arachnoids, as
well as to the genuine Crustacea.

Class II.

Sub-class I.

Order 1.

ARACHNOIDEA.......

.Head and thorax fused into a single

piece, the cephalo-thorax, bearing six
pairs of appendages, of which one is
prae-oral. These may all be used as legs,
or one or more pieces may be chelate or
toothed and serve as mandibles or wea-
pons of defense. In the lower forms the
abdomen is elongated and segmented and
may bear appendages, but in the higher
forms it is consolidated and may be fused
with the cephalo-thorax. Respiratory
organs originally lamellate gills, devel-
oped as adjuncts of the abdominal ap-
pendages. In the air breathing forms
they may be modified and reduced in
number, or even replaced by a sort of
tracheal system, not homologous with
that of insects.

ARACHNOIDEA BRANCHIATA....Mainly fossil forms, all marine,

Gigantostraka. ..

gills lamellate, one pair of eyes (‘‘ trilo-
bite”) in side of cephalo-thorax, and one
pair of small ones anterior to these near
the middle line. Coxal joints of the legs,
or of some of them forming spiny plates
used in mastication.

Fossil forms with long extended abdo-
men, which may terminate in a spine.
*% Pterygotus.

34

Order 2.

Sub-class IT.

Order 1.

Order 2.

INVERTEBRATE ZOOLOGY.

Xiphosura (Limuloidea)

eh Me Mostly fossil, with three surviving
species—A bdomen consolidated in recent
forms and bearing six plate-like append-
ages, of which the last five bear lamel-
late gills. A long terminal spine at end
of abdomen. The larvae pass through
a ‘‘ trilobite” stage, showing three well
marked longitudinal areas—and without
the terminal spine. Limulus.

ARACHNOIDEA TRACHEATA...Mostly terrestrial forms—breath-

SCOLMIONIG eames. -s eran

Pseudoscorpionidea.....

ing either by gill plates hanging from the
roof of pneumatic chambers, or by tra-
cheal tubes. Both sorts communicate
with the exterior by paired stigmata sit-
uated on the ventral side of the abdomen.
1-6 pair of eyes—generally simple. First
two pairs of appendages employed as
mouth parts, often chelate. Last four
serve as legs.

.Cephalo-thorax of one piece, broad prae-

abdomen of seven segments and narrow,
elongated post-abdomen of five, ending
in a poisonous spine. Mandibles chelate.
Second pair of appendages enormously
developed and chelate. Four pairs of
respiratory chambers. 4 Scorpio.

Cephalo-thorax of one piece. Abdomen
11-jointed, broad and flat, without atten-
uated portion or sting. First and second
pairs of appendages as in Scorpionidea.
Breath by tracheal tubes, which open by
two pairs of stigmata on second and
third abdominal segments. Spinnerets
on the second abdominal segment. Small
animals found under bark, ete.

* Chelifer.

Order 3.

Order 4. Solpugidea

Order 5.

Order 6.

Pedipalpit..2.--..-

Bihalaneordar seers

Arachnida...

INVERTEBRATE

.Entire body a shortened oval.

ZOOLOGY. 35

Cephalo-thorax of one piece. Abdomen
broad and depressed, 11-12 jointed, with-
out antenuated post-abdomen, but in some
cases ending in a long filiform process.
Mandibles with single claw. Second
pair of appendages large and chelate.
Third pair feeler-like, extended like whip
lashes. Two pairs of respiratory cham-
bers on second and third abdominal seg-
ments. x Phrynus.

Head distinct, thorax of three segments,
abdomen cylindrical, 10-jointed—mandi-
bles chelate. Second pair of appendages
leg-like, not chelate. Tracheal respira-
tory system with stigmata on the first
thoracic segment and second and third
abdominal segments. Nocturnal animals
found in sandy parts of the tropics—
bite poisonous. 7% Solpuga.

Reduced
abdomen closely applied to cephalo-tho-
rax, but distinct and consisting of six
segments. Mandibles chelate. Legs very
long and attenuated. Tracheal tubes
with one pair of stigmata between tho-
rax and abdomen. ye Phalangiwm.

Abdomen without segments, swollen and
attached to cephalo-thorax by a stalk.
Mandibles ending in a simple claw with
poison gland. Second pair of appendages
leg-like—modified in male. 2-8 pairs of
spinnerets at end of abdomen. 1-2 pairs
of respiratory chambers situated on ab-
domen. These may be also connected
with a system of tracheal tubes.

*% EHpeira.

36

Order 7. Acarina

Pantapoda.

Tardigrada

INVERTEBRATE ZOOLOGY.

a ar Abdomen fused with cephalo-thorax.

Body unsegmented. Appendages about
mouth often modified to form a sucking
tube. Respiration by tracheal tubes or
merely through integument in smaller
forms—many parasitic.
* Ixodes, Tyroglyphus.

SUPPLEMENTARY GROUPS.

........Hxtremely attenuated marine forms with

long slender legs and body of about the
same diameter. Cephalo-thorax of six
segments, of which the first are fused,
possessing a beak at the anterior end.
Abdomen much reduced and _sac-like.
Seven pairs of legs, containing the repro-
ductive organs and diverticula of the
stomach. Respiratory organs fail.

*% Nymphon.

al ere Mr Minute fresh water forms, with four

pairs of short legs bearing little hooks.
Hermaphroditic—without heart or organs
of respiration. 4 Macrobiotus.

Pentastomidea (Linguatulina).....Parasites in the lungs and nasal cavities

of reptiles and mammals. Long, flat-
tened worms, resembling Taeniae, but
with Arachnoid development. Legs re-
duced to two pairs of hooks about the
mouth. + Pentastomum.

Class II. TRACHEATA ANTENNATA.. .Head always distinct, never fused

with thorax, one pair of antennae, breathe
by system of tracheal tubes opening by
stigmata.

INVERTEBRATE ZOOLOGY. 37

Sub-class I. ONYCHOPHORA .. ... This includes one genus of widely sepa-
rated species, intermediate between An-
nelids and Myriapods. The body is worm-
like, each segment bearing a pair of
limbs with indistinct articulations, thus
resembling parapodia. Paired nephridia
of Annelid type, opening at the base of
the feet. A richly branched tracheal
system, opening by irregularly dispersed
stigmata. ye Peripatus.

Sub-class II]. MyriapoDa ... ..... Head with antennae, mandibles, and two
pairs of maxillae. No differentiation of
thorax. Each segment bears a pair of
legs, alike in shape and size.

Orderel-aeChilopodane-.--ie see: Mainly depressed in form. One pair of
legs to each segment. Mandibles well
developed, fitted for predaceous life.
First pair of legs transformed to a pair
of jaws furnished with poison glands.
Reproductive opening at posterior end of
body. > Lithobius, Scolopendra.

Order 2. Diplopoda....... .. ...A double pair of legs to each segment.
Maxillae united to form a complex under-
lip, the gnathochilarium. Reproductive
opening at base of second pair of legs.
*% Lulus.

Sub-class. Hexapopa (Insecta).....Body divided into three distinct regions,
or segment-complexes, head, thorax and
abdomen. Mouth parts typically of three
component parts, the mandibles, and the
first and second maxillae, which may be-
come strongly modified in adaptation to
very varied life habits. Thorax of three
segments, each one with a pair of legs.
The last two segments in higher insects
bear each a pair of wings formed by an
integumental duplicature and directly de-
rivable from ‘* tracheal gills,” a modifica-

38

Order 1.

Order 2.

Order 3.

Order 4.

Order 5.

Thysaneura

Pseudoneuroptera. ....

INVERTEBRATE ZOOLOGY.

Orthopterai). 0% ek

Neuropteraseecs essen

Coleoptera

tion originally for aquatic breathing and
still retained in a few aquatic larval
forms. The higher insects have gained
secondary larval forms and thus develop
by a metamorphosis.

Soyer yen a Minute wingless forms, with biting

mouth parts, found in decayed wood
and damp earth. They are the most
primitive insects and have never devel-
oped wings. Some show rudiments of
of abdominal legs. Ametabolic, i. e. de-
velopment direct. 4% Podura.

.Mouth parts biting, wingsall alike, trans-

parent, delicate, with lace-like venation.
This group was formerly united with the
Neuroptera, but has an active pupa
(hemimetabolism).

* Libellula, Ephemera.

Mouth parts biting—upper wings parch-
ment-like, generally narrow — under
wings membraneous and often folded.
Development hemimetabolic i. e. pupa
active. 4 Caloptenus.

Mouth parts biting—somewhat modified
in Phryganidae. Wings as in Order 2.
Development holometabolic i. e. pupa—
quiescent. 4 Phryganea.

Mouth parts biting—upper wings (clytra)
forming hard shields for the protection
of the membraneous lower ones. Holo-
metabolic. Thorax free and quite dis-
tinct from the posterior portion, thus
dividing the body into three regions,
head, pro-thorax, and meso- and meta-
thorax + abdomen. Holometabolic.

*% Carabus.

INVERTEBRATE ZOOLOGY. 39

Order 6. Rhynchota (Hemiptera).. Mouth parts modified to form a straight

Order 7. Lepidoptera ..

jointed beak, which lies between the
coxal joints of the legs. Wings either
membraneous and alike, or with the
outer diagonal half of the upper wings
pergamenteous. Many forms wingless.
Hemimetabolic. 4 Coreus, Cicada.

Mouth parts a double coiled proboscis,
formed by the first maxillae. Wings
alike in texture, membraneous, covered
with minute colored scales. Holometa-
bolic. ye Papilio, Sphine.

Orderkss eDipteradeasa- sess lee: Mouth parts variously modified, sucking,

Order 9. Hymenoptera.

Cladus II. Mollusca.

Class I. AMPHINEURA

piercing or lapping—never biting. Fore
wings membraneous, hind wings reduced
to minute knobs—the so-called balancers.
Holometabolic.

*% Culex, Musca.

Mouth parts biting—or biting and lap-
ping. Wings membraneous, alike in text-
ure, but hind pair reduced in size. Body
generally much constricted between tho-
rax and abdomen. Ovipositor of male
generally accompanied by organs for
sawing, boring or digging, and in some a
venomous sting. Holometabolic.

*% Vespa, Formica.

A small group of bilaterally symmetrical
marine molluscs with very primitive
characteristics. They have a nerve ring
around the mouth, from which pass two
lateral and two ventral nerve cords con-
nected by transverse commissures.

40
Order 1. Solenogastres.........
Orders2seChitonest car ice
Class II. LAMELLIBRANCHIATA....
Order ey siphomiateiaee es ee

Sub-order 1.

Sub-order 2.

Order 2. Asiphonia........-.

Sub-order 1.

a)

Sub-order 2.

Sub-order 3.

Sinupalliata. ...

Integripalliata....Siphons short, not contractile.

Homomyaria. . .

Heteromyaria. ..

Monomyaria......

INVERTEBRATE ZOOLOGY.

..Worm-like forms without mantle or

shell, but with calcareous spicules im-
bedded in the cuticula. Some possess a
ciliated ventral furrow, in the bottom of
which lies arudimentary foot. In others
furrow and foot fail. 4% Proneomenia.

Depressed forms with a dorsal shell com-
posed of eight transverse pieces. Cteni-
dia in two longitudinal rows between
foot and edge of mantle. Foot large,
with oval, flattened creeping surface.

* Chiton.

..Bilaterally symmetrical Mollusca with

four (in a few cases two) plate-like gills,
and with two lateral shells generally
united dorsally. They are without a dis-
tinct head and lack a ‘‘ lingual ribbon”
or radula. The foot is compressed and
never forms a creeping disc.

.With two posterior siphons, separate or

fused. Edges of mantle often joined.

Siphons long and contractile. Mantle
line with sinus. ye Mya, Venus, Solen.

No pal-

lial sinus. ¥& Cyclas.

. .Siphons absent.

Anterior and posterior adductor muscles
about equal. 4% Unio.

.Anterior adductor very small.

*& Mytilus.

Anterior adductor wanting.
*% Ostrea, Pecten.

Class III.

INVERTEBR

SCAPHOPODA...........-

Class LEV). (GASTEROPODA.... .....-

Order 1.

Order 2.

Order 3.

Prosobranchiata........

Heteropoda. .........-

Pulmonata

ATE ZOOLOGY. 41

Bilaterally-symmetrical forms with body
cavity greatly elongated in a dorso-ven-
tral direction. Mantle and shell tubular
and somewhat curved, with a smaller
dorsal and a larger ventral opening.
Ctenidia fail. Foot elongated and coni-
cal. A single family of marine forms.
* Dentalium.

Molluscs with a head, foot and visceral
sack. The first two are bilateral, the
third is almost invariably unsymmetri-
cal, the pallial complex, with its organs
being developed upon one side only (usu-
ally the right). The visceral sack is
generally contained in a spirally twisted
shell, wound usually toward the right
about a central axis, and capable of re-
ceiving the other parts when contracted.
The mouth is furnished with a radula;:
the foot generally forms a creeping disc.

Shell present, ctenidium anterior to
heart ; foot a creeping disc ; bisexual.
% Oliva, Conus, Cypraea, Strombus.

Shell small or wanting. Gill as in pre-
vious order. Anterior part of foot com-
pressed, forming a sort of keel. Bisex-
ual. This order includes a very few
nearly transparent forms, which swim on
the surface of the ocean. They may be
considered as Prosobranchiata adapted to
a pelagic life. > Carinaria.

Land and fresh water snails, breathing
by plexus of blood vessels, which lie in
a respiratory chamber communicating
with the exterior, and placed anterior to
the heart. Ctenidia fail. Shell generally
present. Hermaphroditic.

* Helix, Limnaea,

42

INVERTEBRATE ZOOLOGY.

Order 4. Opisthobranchiata......

Order 5.

Pteropoda......

Class) Ve. CERHATLOPRODALE A eee ernee

Order 1.

Order 2,

Tetrabranchiata

Dibranchivatae- eee

Shell delicate or wanting. Respiration
seldom by ctenidia, often by secondary
or adaptive gills, or through the integu-
ment. Gills, when present, lie behind
the heart. Back of naked forms often
ornamented with simple or dendritic
papillae. Hermaphroditic.

* Bulla, Eolis.

Shell fragile or wanting, foot developed
into a pair of wing-like expansions.
Hermaphroditic. A small group of forms
which swim at night upon the surface of
the ocean—often referred to preceding
order, from which they have undoubt-
edly been derived. ye Cymbuliopsis.

Body bilaterally symmetrical, extended
in a dorso-ventral direction and flattened
antoro-posteriorily so that the anterior
aspect seems dorsal, the posterior ven-
tral, the dorsal posterior, etc. The
greatly modified foot forms a series of
tentacles about the mouth and a funnel
or infundibulum behind it. The head is
large and distinct, with two large prom-
inent eyes. Mouth provided with a pair
of chitinous jaws. Shell large and cham-
bered, or reduced or even internal.

Gills four, mouth surrounded by numer-
ous unarmed tentacles. Ink bag fails.
A heavy external shell convoluted and
divided into chambers—the animal being
in the terminal and largest one.

* Nautilus (only living form).

.Gills two. Eight (or ten) arms around

the mouth, covered with cup-shaped
sucking discs. Ink bag present. Shell
internal (a very fragile external shell in
Argonauta), % Octopus, Loligo, Sepia,

INVERTEBRATE ZOOLOGY. 43

The present Cephalods are the few degenerate descendants of a very large
and abundant group, which filled the seas in Palaeozoic and Mesozoic times.
They possessed, originally, well developed shells, divided into chambers ; some
shells being straight, others spirally coiled. The orders of NAUTILOIDEA and
AMMONOIDEA were Tetrabranchs, the BELEMNOIDEA Dibranchs.

Cladus III. Molluscoidea.

Class I. Bryozoa (Polyzoa)........Minute forms, usually colonial. At an-
terior end a ridge, the lophophore, which
bears ciliated tentacles. Anus situated
outside the lophophore.

Order 1. Phoronidea... .........Worm-like forms, enclosed in leathery
tubes. Larva free-swimming—the ‘‘ Ac-
tinotrocha.” Similar to the trochophore
—one genus. Phoronis.

@rder;2)) Ketoprocta.. ...- 2... - Typical forms, nearly always forming a
colony, which resembles an alga. Each
animal is enclosed in a transparent cell,
from which it may extend its tentacles,
and into whichit may entirely withdraw.
A few fresh water forms, the rest marine.
* Bugula, Plumatella.

Class Il. BRACHIOPODA...........-/ All marine, depressed in form, with dor-
sal and ventral shells, which are sym-
metrical, but unequal. Mouth situated
between two spiral ciliated arms, which
lie coiled up in the shell—a large fossil
order. Few living.

Ordengl-eLCALCINGS re se: Shell without hinge. »& Lingula.
Order 2. Testicardines... .......Shell with hinge, usually calcareous

loops to support arms. ¥& Terebratulina.

Type V. AMBULACRALIA.
Cladus. Echinodermata.

Classs) SHOLOTHUROIDBA...--:-.-- Adult creeping or sessile, oval or vermi-
form, covered by a leathery integument
in which minute calcareous spicules,
plates, etc., lies imbedded, Around the

44 INVERTEBRATE ZOOLOGY.

Orders edataesensn eee erie

Orderses Amodagae... oan =

Classen VCRINOIDE ACNE See eae

[The following fossil classes belong here.
Claissh BGYSPUD WAC eis) .i0ejeie nie eis = siete viele

@lass. BEASTOMD EA. ccs ateeiale'saiteielere

Glassell -ASTEROIDWAH se oe

Orokere il, . A\eweravelen 565 Géciccodoce

Order 2. Ophiuridea........

GlasssDVen LICHINOIDH A oh e a eeee ce

mouth is a crown of fringed retractile
tentacles. Ambulacral feet, either in
rows, or irregularly disposed, or wanting.
Larval form the Awricularia—reduced in
some cases.

Ambulacral feet present.
*% Pentacta, Thyone.

..Ambulacral feet wanting. » Synapta.

Mostly sessile, flower-like forms; with
stem, calyx and many-branching arms
covered with pinnulae. Very few living
forms—many fossil. Free-swimming
larval form oval, with ciliated bands.

* Pentacrinus.

They are often included among Crinoids:
Mostly with arms, calyx plates irregular.
Without arms, calyx plates regular.]

Adult star-shaped to pentagonal, with
exo-skeleton in the form of a rough net-

work, studded with fixed spines. Ambu-
lacral feet in grooves on oval side.

No clear distinction between mouth and
arms. Larval form the Bipinnaria and
Brachiolaria. 4 Asterias.

.Disc and arms distinct, the latter serpen-

tine and very brittle. Larval form a
Pluteus, similar to that of Echinoidea.
* Ophiopolis.

Adult spheroidal, oval or disc-shaped,
with exo-skeleton composed of solid cal-
careous plates arranged in meridional or
radial rows. The surface of this shell is
beset with spines which rotate upon tu-
bercles. Rows of ambulacral feet pro-
ject from foramina in shell,

INVERTEBRATE ZOOLOGY. 45

Sub-class I. PALECHINIDA.......... Shell with more than twenty rows of
plates—all fossil.

Sub-class II. HEUCHINIDA........... Shell with twenty rows of plates, ten
ambulacral and ten interambulacral.

Order i>) Resularias = 5..-+ 425. Mouth and anus in the center of their
respective surfaces.
* Strongylocentrotus.

Order 2. Clypeastroidea......... Mouth central, anus eccentric.
* Echinarachnius.

Order 3. Spatangoidea........... Mouth and anus both eccentric.
* Spatangus.

Type VI. CHORDATA.
Cladus I. Hemichorda.

This Cladus was founded for a single genus of worm-like marine forms,
found in mud-flats. At the anterior end is a long, flexible proboscis, with
which the animal pushes its way through the mud: at the base of this is a
narrow zone, the collar, at the upper ventral edge of which the mouth is situ-
ated. This is followed by a long worm-like body, showing paired gill-slits on
its ventral aspect. The main details of its structure have been given under
the description of the Cladus, q. v. %¢ Balanoglossus.

[Cephalodiscus and Rhabdopleura, two sessile forms classed as Order, Pterobranchia, un-
der Bryozoa, have been found to resemble Balanoglossus. In young buds of the former a
division into proboscis, collar and body may be seen. There are also a single pair of gill-
slits, and a dorsal diverticulum of the intestine (notochord ?”) lying under the dorsal ner-
vous system. In Rhabdoplema no gill-slits have been detected, but in other respects the
structure is similar to Cephalodiscus. HEMICHORDA may thus be represented by two
classes: Class I, ENTEROPNEUSTA, including the different species of Balanoglossus, and
Class II, PTEROBRANCHIA, including the two forms under consideration. ]

Cladus II. Urochorda.

Class J. PERENNICHORDATA........ Free-swimming forms, like the larvae of
higher tunicates. They possess a long
tail provided with a skeletal axis, the
notochord. Pharynx with a single pair
of gill-slits. No definite mantle, but a
gelatinous envelope. ye Appendicularia,

46 INVERTEBRATE ZOOLOGY.

Class il. ACADUCICHORDAVIAG serene Tail and notochord present only in larval
life.
Sub-class I. AScIDIACEA............ Body sack-like. Pharyngeal wall form-

ing a sort of lattice-work. Excurrent
and incurrent orifices generally approxi-
mated.

Order 1. Ascidiae.................Sessile forms, either solitary (monasci-
diae), or colonial (synascidiae) and ar-
ranged in generally stellate groups,
known as coenobia.

* Boltenia, Botryllus.

Orders2 sey rosomiae ses ane Free-swimming, transparent colonies of
cylindrical or cone-shaped forms. Incur-
rent openings upon the exterior, cloacal
openings in the interior. ye Pyrosoma.

Sule ss) JI; WMEWAIIDNOIWIN js ccaue. doc Free-swimming, transparent cask-shaped
forms. Pharynx with two rows of small
gill-slits, or a single pair of large gill-
slits. Oval and cloacal openings at oppo-
site poles—often with alternation of gen-
erations.

Orderel. .Doholkdacweaee esse ene Two rows of gill-slits. Muscle-bands in
the form of closed rings. Mantle thin—
generative cycle including one sexual and
two asexual generations. 4 Doliolwm.

Order 2. Salpidae ... .............4 single pair of gill-slits. Muscle-bands
not as complete rings. Mantle thick.
Alternation of generations simple, soli-
tary asexual individuals alternating with
a chain-like series of sexual forms.
*& Salpa.

Cladus III. Cephalochorda.

This group includes but two closely allied genera. The anatomical details
are given in the definition of the Cladus—q. v. % Amphioxus.

INVERTEBRATE ZOOLOGY. 47

Cladus IV. Vertebrata.

Sub-cladus I.

Cyclostomata.

This Sub-cladus includes two groups which may have the value of families.
For general anatomical details see the definition of the main group.

Family I.

Family 2.

Petromyzontidae......
(Lamprey eels.)

GI TEUTULOLC eat tetera
(Hag-fish. )

Sub-cladus II.
SAUINGASMINNEAY Ay nczte ac areiae

Division [.

CLASS ele SE ISCHS. 2h cchat ars coke Nota tnaes

Order 1.

Order 2.

Nasal cavity a median blind-sack. Mouth
without tentacles. They attach them-
selves by their circular mouth to the
sides of fishes and suck their blood.
Fresh water and marine forms.

*% Petromyzon.

Nasal sack provided with an inner pala-
tal opening. Mouth with tentacles.
Habits more parasitic than the former.
They push their way even into the body-
cavity of other fish and consume their
viscera. All marine. » Myxine.

Gnathostomata.

Amnion and other embryonic membranes
fail. Breathe by gills during at least a
portion of their life. Mesonephros func-
tions as permanent kidney.

Aquatic Anamnia, with branchial respir-
ation. Paired limbs in the form of fins
(Ichthyopterygium). Integument gener-
ally produces scales, which contain bony
material produced by the corium. Head
with one auricle and one ventricle.

Selachii (Elasmobranchii). .Skeleton cartilaginous, scales placoid.

Ganoidei

Tail heterocercal. 5-7 separate gill open-
ings without operculum. ye Squalus.

Skeleton more or less reinforced by bone.
Scales overlaid with enamel and typically
rhomboid in form (ganoid). Tail hetero-
cereal, Gill-slits with operculum,

48

Sub-order 1.

Sub-order 2.

Order 3.

Sub-order 1.

Sub-order 2.

Group

Group.

Group

Group

Group 5.

Class# ll @DIPNOIG== eee eee

INVERTEBRATE ZOOLOGY.

Chondrostei......

Notochord an unsegmented cartilaginous
rod, upon which the arches and other
vertebral elements rest. Integument with
rows of bony plates, or naked.

*% Accipenser, Polyodon.

FAOLOSUCU meer: Notochord with bony constrictions, cor-

Meleostelicne eens eee

vo

Ty SOSGONUUs eae

IVY SOCLUSUU teers

Anacanthini......

Acanthopteri.....

Pharyngognathi. . .

Plectognathi.......

Lophobranchit.....

responding to the vertebral centra.
Skull with membrane bones.
% Lepidosteus.

Skeleton osseous. Scales cycloid or cten-
oid. Tail homocercal. Gills provided
with an operculum.

Swimming bladder provided with a pneu-
matic duct. Ventral fins abdominal.
Fin rays soft. Almost all the fresh
water fish belong here. 4 Salmo.

Swimming bladder without connection

with alimentary tract, often wanting.

.Fin rays weak. Ventral fins anterior to

pectoral. 4 Gadus.

Some fin rays spinous, at least of the

dorsal fin. Inferior pharyngeal bones
separate. The largest group of Teleosts.
x Scomber.

.Some fin rays spinous. Inferior pharyn-

geal bones separate. ye Labrus.

A small group of very compact forms.
Maxilla and prae-maxilla immovably
joined with skull. 4 Diodon.

Gills tufted, eggs carried by male in a
brood sack. Body covered by large
plates. 4% Hippocampus.

-... Skeleton mainly cartilaginous. Noto-

chord persistent. Paired fins with a cen-
tral skeletal axis and with or without

INVERTEBRATE ZOOLOGY. 49

i lateral rays. Median fin continuous
around tail. Swimming-bladder func-
tions as lung. Gills with operculum.
In one species small external gills. A
very small, but isolated group, including
3-4 species. These represent two orders.

Order 1. Monopneumones........Lung (=swimming-bladder) single.
* Ceratodus.
Order 2. Dipneumones.......... A pair of lungs present. 4 Protopterus.
Class III. AMPHIBIA................Skin naked, very glandular and slimy.

Gills, external and internal, present at
some stage, generally transitory. Lungs
usually present, with larynx and trachea.
Paired limbs of the hand-form (cheirop-
terygium) with normally five digits, often
reduced in number. Two occipital con-

dyles.
Ordenwile -Wrodelaere cc .vo5 tease: Body elongated. Tail persistent.
Sub-order 1. Perennibranchiata....With external gill-bushes and me-

dian fin in caudal region. ye Necturus.

Sub-order 2. Derotremata......No external gills, but with a persistent
gill-slit. 4% Menopoma.

©

Sub-order 3. Salamandrida....External gills and gill-slits embryonic or
larval. Adult breathe by lungs, or by
pharyngeal and integumental respira-
tion, the lungs failing.

* Salamandra, Desmognathus.

Order 2. Gymnophiona.......... Serpentine subterranean forms without
tail, limbs or gills. Integument with
minute scales sunken in pits. > Coecilia.

Ordemio.) CANOUBALH ass sues See a Compact, cephalized forms, with tail
present only in larval life. Hind legs
enormously developed and used for leap-
ingandswimming. No gills when adult.
*% Rana, Bufo.

50

Division Il. AMNIOTA

INVERTEBRATE ZOOLOGY.

Classe Ve REE DAG yer creer

Sub-class I. PLAGIOTREMATA...

Order 1. Lacertilia

Sub-order 1.

Sub-order 2.

Sub-order 3.

Sub-order 4.

Fissilinguia......

Brevilinguia.....

OCrassilinguia. ...

Vermilinguia

Embryo furnished with amnjon and al-
lantois. Mesonephros and its duct pos-
sess an excretory function only in the
embryo, being replaced in adult life by
the definite kidney (metanephros). The
mesonephros then disappears, except cer-
tain portions, which are utilized by the
reproductive system.

Integument covered with scales, horns,
and other structures of epidermic forma-
tion. Glands confined to a definite local-
ity (femoral glands of lizards) or want-
ing. Gills never developed, embryonal
gill-arches modified to subserve other
functions. A single occipital condyle.

..Cloacal opening transverse, behind which,

in the male, are paired organs of copula-
tion. Body uniformly covered by deli-
cate scales, which are cast off yearly
often as a single piece. Habits terres-
trial and arboreal. Quadratum mova-
bly articulated with skull.

Four well-developed limbs in the typical
gano, and sternum or shoulder girdle
present in forms with reduction of limbs.

Tongue long and slender, extensile,
forked at the end. 5 Lacerta.

.Tongue short and thick, thin and notched

at tip. Limbs sometimes fail. > Anguis.

-Tongue short and thick, rounded at tip,

not extensile. + Iguana, Gecko.

Tongue very long, vermiform, thickened
at tip. + Chameieo.

INVERTEBRATE ZOOLOGY. 51

Sub-order 5. Annulata.... ...No limbs or eyelids—Epidermis divided
into oblong fields by longitudinal and
transverse forms. ye Amphisbaena.

Order) 2 Ophidia. =. :2--+2.- ....Body very much attenuated, limbs fail,
no rudiment of shoulder girdle or ster-
num. A single lung developed (right).
Other paired organs placed the one be-
hind the other. 4 Crotalus, Python.

[A single species of a very ancient type of lizard occurs in New Zealand, Sphenodon (Hat-

tena) punctata. The quadrate is immovable, ventral ribs and abdominal sternum are pres-
ent, the vertebrae are amphicoelous. It is referred to the Order Rhynchocephalia.]

Sub-class II. HyDROSAURIA........ Cloacal opening oval in shape, its longer
axis longitudinal. A single organ of cop-
ulation in the male, anterior to the cloaca.
Scales large and irregular, often rein-
forced by bony plates, which may
coalesce to form dorsal and ventral
shields. Mainly aquatic in habits. Quad-
ratum immovably attached to skull.

Order 1. Chelonia................Body enclosed by dorsal and ventral
shields, formed partly by elements of the
endo-skeleton and partly from the integ-
ment. Teeth replaced by horny beak,
with sharp cutting edge.

*% Chrysemys, Chelone.

@rderocs Crocodilia..ss-..--..--- Body elongated, covered by large plates,
which do not coalesce. Thoracic and ab-
dominal sterna present, connected by
ventral and dorsal ribs. Teeth large, in
alveoli. ye Alligator.

[Our knowledge of Reptilia is greatly increased by the discovery of several fossil classes
and orders. The PTEROSAURIA were allied to the Lacertilia, and possessed membraneous ex-
pansions of the integument of the arms and fingers, by which they could fly. The PLEIsIo-
SAURIA and IcHTHYOSAURIA were hydrosaurs, the former somewhat resembling turtles, the
latter crocodiles. The DrnosAuRIA included some enormous terrestrial forms with massive
skeletons, Brontosaurus, Igwuanodon. Other smaller Dinosaurs may have been the precursors
of birds. They walked mainly upon their hind feet, possessed pneumatic cavities in their
bones. and showed many other avian characteristics. An important form is Compsognathus
(one specimen at Munich) which shows affinity to Archaeopteryx (see introduction to Aves)].

52 INVERTEBRATE ZOOLOGY.

Classy Vis WIASVIES Teta Fc vedere sonst eriee Warm-blooded Vertebrates, showing
many reptilian characters, but differing
from them in the possession of feathers.
These are epidermic structures closely
related to scales. The anterior limb is
modified to form a wing, generally giving
the animal the power of flight. Quad-
rate bone movably articulated with the
skull. A single occipital condyle.

[Some have recommended the fusion of Reptilia and Aves into a single class, Sauropsida,
which is warranted not only on anatomical grounds, but by the possession of intermediate
fossil forms. It seems, however, more practical to retain them as separate classes, which if
we take living forms alone into consideration, is easy to do. The following fossil groups
may be given, preceding the living forms. They should have the value of Sub-classes:

SS ACR UA epee teiereolclefelerolelelelnisieisielesieloisieteisie Jaws containing teeth, tail elongated, containing
a large number of vertebrae, with a pair of con-
tour feathers to each. Digits of the wing not
coalesced, three being armed with claws.

* Archaeopteryx.

ODONTORNIDHES 2 cjaceig oa olsinieisieia\ae)e le inie Bird-like forms similar to recent birds, but with
teeth in both jaws, inserted either in separate
alveoli, or in acommon groove. There are two
groups of these birds, one having akeelless ster-
num allied to the Ratitae, the other with a keeled
sternum and allied to the Carinatae.
*Hesperornis, Ichthyornis. |

Sullo=@1ASsie lee AGITUAU erste eet eys Breast bone flat. Clavicles not united to
form a furcula. Feathers down-like or
plume-like. Running birds with small
or rudimentary wings. Cannot fly.

*% Struthio.

Sub-class II. CARINATAE ..........Breast bone keeled. Furcula generally
present. Contour feathers on wings and
tail.

Orderae. Gallinacetn. estar Feet stout, for scratching. Hind toe on

a higher level than the others. Edge of
upper beak shuts over lower beak. Sec-
ondary sexual characters common, in
form of combs, wattles, spurs, etc.

* Gallus, Perdix.

INVERTEBRATE ZOOLOGY. 53

Orders) Colmmbini:ce.-+.:-26

OrdersoemNauabOresaa.. a...

Order 4. ‘Grallatores.............

@rdere). ) sGansores--..o.s scene.

Orders Measseresi son es eses ue

Order

=e

RapvOnesae sea eerecers

Classeivaley sc VPA MIMATS WAS seers eye, oe

Legs short, hind toe on a level with the
others. Edge of upper beak in contact
with that of lower. At base of upper
beak two outgrowths covering the nos-
trils. 4 Columba.

Aquatic birds with oily feathers and
short webbed feet. 4 Anser, Larus.

.Wading birds with very long slender

legs, and toes without webs. Often the
lower half of the tibia is free from feath-
ers. Neck and bill very long and slen-
der. » Grus, Scolopax.

Climbing birds. Inner forward toe re-
versible, giving the foot two toes in front
and two behind. Several groups of birds
belong here, not closely related.

* Psittacus, Picus.

The most numerous group. Feet fitted
for perching. Two groups, the Oscines,
or singing birds, which have developed
a special organ, the Syrinx, at the fork-
ing of the bronchi: and the Clamatores,
without this. 4% Fringilla, Cypselus.

.Birds of prey. Toes furnished with

hooked claws or talons. Point of upper
beak sharp and talon-like, projecting over
the lower one. ye Aquila, Strix.

Warm-blooded vertebrates. Body clothed
with hair; young nourished by milk, a
secretion of integumental glands. Quad-
rate in middle ear, two occipital condyles.

Sub-class I. MONOTREMATA........ Low oviparous mammalia with reptilian

characteristics. The young, immature
when hatched, are brooded either in a
nest or in a brood pouch temporarily de-
veloped. No localized mammary glands;

54 INVERTEBRATE ZOOLOGY.

Sub-class II. MARSUPIALIA...

Order Me sZOOPMALL ris. lc ene cer

Orden 2a ehytophagivescs erect

Sub-class III. PLACENTALIA.......

OrdersieeeHdentatansneee eee <

@OrdersoseCetaceas «..oe men eee

the ‘‘ milk” is a secretion of perspiratory
glands, richly developed in a certain area,
the mammary pocket, and thus not
strictly homologous with the milk of
other mammals. Alimentary canal,
urethra, and reproductive ducts open into
a common cloaca.

* Ornithorhynchus, Echidna.

.. Viviparous mammals without placenta.

The young are born ina very immature
condition and brooded in an external ab-
dominal pouch, the marsupium. Two
lateral uteri imperfectly united. Divi-
sion between anus and sinus uro-genitalis
internal and indistinct.

.Carnivorous marsupials with pointed

teeth and well developed canines.
% Didelphys.

Herbivorous marsupials with flat teeth
and reduction of canines. y Macropus.

. Young nourished in uterus of mother by

a capillary mass, the placenta, which ad-
heres to the uterine wall and is connected
with the embryo by the umbilical cord.
Anus separated from the uro-genital
sinus by a perinaewm.

.Teeth either wanting or in condition of

retrogressive metamorphosis. Incisors
and canines generally fail. Large num-
ber of sacral vertebrae. 4 Dasypus.

Aquatic forms with naked skin, provided
with hair in embryo. Hind limbs fail
externally. Rudiments under — skin.
Mammary glands in folds on the sides of
the vagina. External nares in top of head
connecting directly with a tubular pro-
longation of the larynx. + Balaena.

INVERTEBRATE ZOOLOGY. 55

€

OrderkoeeeoIneniar ey eesoe eek oes

Order 4. WUnewlatas.. s4ec0 oe eae

Sub-order 1. Perissodactyla...

Sub-order 2. Artiodactyla. ....

Order 5. Proboscidia... .

OrderniGshodentiae sso... sss

Aquatic forms with only the anterior
limbs developed. Teeth often fail ; mo-
lars, when present, resemble those of un-
gulates. Sparsely hairy. A single pair
of pectoral mammary glands.

* Manatus.

.Herbivorous mammals with flattened

molars. Toes often reduced in number,
tipped with flattened hoofs.

.Ungulates with an odd number of toes,

five, three or one, the middle one being
the best developed. Prae-molars equal
the molars in size. Integment often very
thick. ye Rhinoceros, Equus.

.Ungulates with an even number of toes,

of which two, (3 and 4) are the best de-
veloped, resulting typically in the cloven
hoof. The prae-molars, 3-4, are smaller
than the molars. Apart of them are
ruminants. + Bos, Hippopotamus.

.A group allied to the Ungulates, but

with always five stout toes furnished
with hoofs, making a ponderous rounded
foot. The snout is enormously prolonged
forming a muscular proboscis tipped with
a sensitive finger-like process. One pair
of incisors, which develop into mam-
moth tusks. In recent forms it is those
of the upper jaw. (Lower incisors in
Dinotheriun.) x EHlephas.

A group of small animals with teeth fit-
ted for gnawing. One pair of incisors
in each jaw develop into sharp cutting
chisels. Canines fail. The molars are
fitted with transverse ridges for cutting.
*% Mus, Sciurus.

56

INVERTEBRATE ZOOLOGY.

Ordereipaelnsechivierann seen eres

Order.ss)Carnivoras eee eee

Ooder) 95 “Cheiropterar.-.+2 se.

Orders lOherosimiteeen eee eee

Orders eee rimaessets- eee

Sub-order 1.

JACHIOT AA DUD. 3 5600 6

Small insect-eating mammals with all
the teeth prolonged into sharp points.
Canines small or wanting. 4 Talpa.

Beasts of prey with sharp well developed
canines and pointed molars. The toes
are armed with claws, which may be-
come sharp and retractile. There are
two groups, one terrestrial, Fissipedia,
with toes separate, and one aquatic, with
toes strongly webbed, forming paddles—
Pinnipedia. 4& Felis, Phoca.

The only flying mammals. Toes of ante-
rior limb exceedingly attenuated, thus
forming a frame work for a thin leathery
web, which also includes the hind limb
and tail. Thumb of fore limb and all
the hind toes free. Teeth pointed as in
Insectivora. In many respects similar to
the apes, as a discoidal placenta and a
single pair of pectoral mammary glands.
% Vespertilio.

A group of animals closely allied to the
apes, but of a generally lower structure.
Appendages hand-like, with opposing
thumbs, but with a double uterus, and a
diffuse placenta. The nails are devel-
oped into claws.

.Toes with flat nails. Appendages more

or less hand-like, and generally fitted
with opposing thumbs for grasping. One
pair of pectoral mammary glands. Pla-
centa discoidal.

Nose flattened, nostrils separated by a
broad septum, so that their orifices look
outward. Confined to the new world.

*%& Cebus.

INVERTEBRATE ZOOLOGY. 57

Sub-order 2. Catarrhini....... Internasal septum thin. Nostrils look
forwards and downwards.
% Cercopithecus, Gorilla.

Sub-order 38. Anthropini.......Nose as in Sub-order 2. Thumb more
movable — great toe less so. Hair re-
duced. Erect position normal. ye Homo.

[There are three main races of men, which are thought by some to have the value of spe-
cies. Their characteristics and distribution are as follows:

MOM INCOROES rans eel cclsisio sie Aeicoeeeor Hair curly, oval in cross-section, skin densely
pigmented, nose fiat, lips projecting—includes :
Papuans, Hottentots, Kaffirs and Sudanese.

Cm MONGOULOTSH mde os cerca setacrecicie’s Hair straight, circular in section, skin brown or
g
yellow, cheek bones high, lips thin—includes :—
Malays, Eskimos, Mongols, American Indians.

BS ae COLL COST QUES ateiotate sie cia oie alate se tates Hair wavy or curly, circular in section, skin
white, nose and lips thin—includes :—Semites,
Indo-Europeans, Nubians, Dravidas.]

Gee To Articalata

Tum calle

ie yim’
a Ze
0

. Boalawo gloss uS

”
°
ye)
Ps
“p Blostaea
& ——————
: |

Coloncal Protozoa 4

|

S iw ple ProToqoa

Provisional phylogenetic table, to express the relationships of the main
groups as given in the Synopsis. Hypothetical ancestral forms are under-

scored twice, larval forms once.

I]. Laboratory Practicum.

LABORATORY PRACTICUM.

PROTOZOA.

I. Proropnuasta. (‘‘ Rhizopods” in restricted sense.)

These are minute globules of protoplasm, i. e. ‘‘ cells” without cell wall.
Some are naked, others protected by a shell. Occur in enormous quantities in
slime at bottom of ponds and in swamps, particularly in the moisture col-
lected upon bog-moss (Sphagnum).

{. Squeeze out a drop of water froma tuft of Sphagnum ; let it fall in
the center of a clean slide ; cover and examine 100". cf. Leidy, Plates. Study
several drops in this way and identify. If a form is interesting, bring it to
the center of the field and adjust higher power 300-600".

9. Collect a few slimy leaves and sticks from a stagnant pond or ditch.
Place in a shallow dish with water from the same place. [This is best trans-
ported in a closed can.] Puta drop of this water upon a slide, mix with it
the scrapings from a slimy leaf, cover and examine as above. (Continue the
above investigations [1 and 2] until you have identified three of the follow-
ing forms :—Amoeba, Difflugia, Euglypha, Nebela, Arcella, Hyalosphenia,
Quadrula, Cyphoderia. Make a drawing of each of the three forins. noting
the structure and the character of the shell when present.)

3. Study of living forms. Life is indicated by the movement of the
protoplasm. Amoebae will always be found alive, as so minute a drop of
dead protoplasm would disintegrate at once. On the other hand, the shells
of the other forms are very enduring and are often empty. In such shells a
deceptive appearance of life may be caused by swarms of minute infusoria,
etc., which sometimes inhabit them.

3. «. If the form is an Amoeba, draw several successive shapes. Note
the granular endoplasm and clear ectoplasm. Are the pseudopodia pointed or
blunt? [cf. Leidy for different species.] Study the particles of food. What

(60)

INVERTEBRATE ZOOLOGY. 61

do Amoebae eat? Can you find a circular pinkish object that appears and dis-
appears? This is the contractile vacuole. Can you see the nucleus? This is
also circular and like the surrounding protoplasm, but more refractive.

3. 0b. In case of most shelled forms, the protoplasm cannot be well ob-
served through the thick walls of the shell. In these, watch the large aper-
ture of the shell and look for pseudopodia which may project from it, often
for some distance (nearly the longer diameter of the shell). These may be
finger-like (Difflugia) or exceedingly delicate and filamentous (2uglypha). In
some delicate shells (Hyalosphenia, Cyphoderia) the interior protoplasm may
be seen, connected with the shell by tapering threads. Encysted forms may
be observed without pseudopodia, and the protoplasm in the form of a sphere
within the shell.

3. c. Keep watch for reproducing Rhizopods. In the shelled forms the
new one grows from the aperture of the shell. When fully formed one sees
a pair of shells placed mouth to mouth.

4. (This experiment is not an essential one, but valuable for comparison).
The ‘* white blood corpuscles” or Leucocytes are amoeboid cells with nucleus
and pseudopodia. They occur in the blood and lymph as well as in the saliva
and in the alimentary canal. They may be studied for comparison. Im-
merse a fine needle in 100% Alc. to cleanse it; when dry again, prick the
finger with it, and bring a drop of blood upon a slide. Dilute with clear
saliva, free from bubbles, and cover. (The saliva is the best fluid for diluting
the blood. It keeps the form of the red corpuscles and is itself rich in leu-
cocytes.) Search for lencocytes. When found, examine for several minutes
300-600" and observe the changes of form. These are rendered extremely
slow by the lowering of the temperature and soon stop. (cf. the difference be-
tween 98.6° F., the temperature of the body and that of the microscopic
stage.) The movements are better seen by use of the *‘ warm stage,” an ap-
paratus which heats the preparation by means of an alcohol lamp, or by using
the blood of some animal of lower normal temperature, as the frog.

If. HELIOZzOA.

These are radiate, free-swimming forms, found in clear water, captured
best by the towing net. They are thus difficult to find and never at hand
when wanted. Bear them in mind, however, and be ready to recognize the
first one you meet in subsequent study of pond water. When one is found,
study and draw it, and if possible identify it by Leidy.

62 INVERTEBRATE ZOOLOGY.

Ill. FORAMINIFERA

These are marine and cover with their shells the bottom of the ocean over
vast areas, and often at great depths. In such places the ‘‘ ooze” dredged
from the bottom is mainly composed of Foraminifera shells.

5. Pour out a little of the dry ooze into a watch crystal and examine
with dissecting microscope. Find as many different shapes as possible. A
common form is the Globigerina form (several genera) a series of spheres of
different sizes, irregularly heaped together. Another common shape is Rota-
lia, and allied forms ; ‘flat and consisting of several chambers arranged in a
spiral.

6. Place a few shells on a slide under a dissecting microscope and add a
drop of HCl. What happens? Of what material do the shells consist ?

7. |The experimental part of this will furnish material for the entire
class, and need not be performed by the student.] Boil gently a quantity of
ooze in a test-tube of 70%. This is to expel air from the separate chambers.
Allow it to settle and then decant off the 70% and replace with 95%. In the
same way add 100% and turpentine, after which the preparation is brought
into a shallow dish. A stay of several hours in each liquid is advisable. To
prepare a permanent mount from this, pipette a drop upon a clean slide, drain
off the excess of turpentine and mount in Balsam. In this preparation ob-
serve the numerous pores, or foramina, through which in life the very numer-
ous filamentous pseudopodia are projected.

IV. INFUSORIA.

8. Placea handful of leaves, flower-stems, ete., with a pinch of sugar
in a beaker of water and allow it to stand a week or two, until the water is of
a greenish yellow color. Such water forms an ‘‘infusion,” and will be found
filled with Infusoria.

[In this as well as in subsequent experiments requiring time, make them as
stated, and pass on to the next, returning to these at the proper time.] The
Infusoria obtained by this experiment are mostly oval flattened forms, the
type being called Paramoecium.

8. «. Bring a drop upon a slide, cover and examine. Study them in full
motion as well as you can. By a little skill you can keep a moving form un-
der continual observation, keeping the left hand on the slide, the right one on
the focal screw and the eye at the microscope. The left hand follows the

INVERTEBRATE ZOOLOGY. 63

movements in an horizontal plane, and the right. controls the up and down
motion. This will only succeed with low powers, for the higher powers limit
the field and exaggerate the velocity.

8. b. Mount a drop in a loose tuft of cotton. The animals will be con-
fined between the threads and are easier to study. Watch their motions and
find out if possible by what organs they move.

8. ¢. Look over several drops, if necessary, until you find a double one
like the figure 8. Watch its movements and seek to explain the phenomenon.

8. d. Staining intra vitam. If Bismark Brown be added to a drop con-
taining living forms, and withdrawn after a few minutes, the nuclei will be
found stained, the animals remaining alive. A colony may be kept alive sey-
eral days in a glass of weak Bismark Brown solution, with the same result.

9. Search among several different localities, i. e. different ponds, swamps,
ditches, etc., as well as the different laboratory aquaria, for other forms of
Infusoria. They may generally be distinguished from other forms by their
rapid movement. Other Protozoa and most one-celled plants move very
slowly or not at all. The few sessile forms show their Infusorial nature by
the possession of cilia and by the movements of the parts of the body. Forms
which are especially to be noted are the following :—

a. The trumpet form, Stentor, a very large green Infusorium.

b. The ‘‘ Bell animalcule.” The commonest forms are: (1) Vorticella, at-
tached by spiral stalks to leaves and stems: (2) Epistylis, a large branching
colony with rigid stems, often found upon the backs of snails ; (3) Cothurnia.
In little cups without stalks, found upon antennae of Cyclops.

¢. Volvox—Colonies of flagellate infusoria arranged in the form of beauti-
ful green globes. Look in these for sexual cells and daughter colonies.

d. Monads—Simple flagellate forms, often green, distinguished by the long
flagellum. Many of these forms are the flagellate stage (swarm-spores) of
fresh water algae.

10. Killa frog, open the rectum and mount ina drop of water a bit of
the slime from its walls. It will generally contain parasitic infusoria. Balan-
tidium similar in form to Paramoecium.

V. GREGARINIDA.

These are vermiform unicellular forms, found as parasites in animals of
every class. The largest ones are visible to the naked eye, but the majority
are microscopic, often living within a single cell. Monocystis is a common

64 INVERTEBRATE ZOOLOGY.

form infesting earth-worms. The adult, often visible to the naked eye. is
found in the body cavity, lying along the wall of the alimentary canal. The
encysted form, filled with pseudonavicellae, occurs in the spermatic vesicles
and is found in one out of about three or four individuals.

14. Open an earth-worm along the mid-dorsal line. from the anterior
end as far as a thickened girdle of lighter color, the clitellum (about the
anterior fourth). Pin it out ina dissecting pan and examine with the lens.
The spermatic vesicles consist of three pairs of very noticeable organs some-
what kidney shaped and covering the alimentary canal dorsally. In infected
specimens, minute white flecks may generally be found scattered over the sur-
face of these organs, and often on the body wall, and other organs in the vi-
cinity. When such a specimen is found, remove to a slidea bit of the infected
portion, tease it out a little and press with a cover glass, but not too hard.
With 50* the white flecks may be seen to be cysts filled with pseudonavicellae.
These vary greatly in size and number contained. Select a small and clear
one and observe separate pseudonavicellae with a high power. Crush a cyst
by pressing a needle upon the cover glass while under observation, 50-100°.
The individuals may thus be isolated and studied separately.

VI. BACTERIA.

{2. Collect in a water drop a very slight amount of the scum floating
upon the top of stagnant water, or water containing decomposing material.
Scum from macerating bones is especially good. Cover and observe with high
powers. Focus high—i. e. for the upper surface of the layer of water. Look
for extremely minute sticks and dots lying in all directions. These are stick
forms. Bacillus and Bacterium. The screw form, Spirillum, is often present.
These may all be in active motion or in a quiescent condition.

13. Make a permanent mount of the above, as follows :

(1) Spread a very thin layer of the material containing Bacteria upon a
cover-glass.

(2) Set aside and allow to dry.

(3) Hold glass in the fingers, preparation side uppermost, and pass quickly
through an alcohol flame 2-3 times. This coagulates the thin pellicle of albu-
men surrounding each individual and thus fastens it to the glass.

(4) Lay the glass down and place upon it a drop of methyl violet, fuchsin,
or methyl blue, and let it stand 3-5 minutes.

(5) Take the glass in forceps and wash off with stream from wash bottle.

INVERTEBRATE ZOOLOGY. 65

(6) Lay it down, preparation side up, and allow to dry.
(7) Place then a drop of Canada Balsam in the center of a clean slide, invert
the cover glass and place it upon the drop.

14. Scrape the inside of the cheek very slightly with a dull knife and
mount a little of the substance obtained in a drop of clear saliva—100". The
field will be filled with large flat cells that look like thin membranes. Find
one that is isolated from the rest and well spread out. Place this under
300-600". In the center will be seen its nucleus, a clear oval mass. Surround-
ing this will be seen numerous round dots, highly refractive. These are ball-
bacteria. Make a permanent mount of this as given above [13].

PORIFERA.

Type I.—An Ascon Sponge.

{5. Place an entire specimen, or group of several, in a watch crystal of
70¢ and study under dissecting microscope. Notice manner of growth, main
body with osculum, and lateral buds. Have any of these oscula? Cut open
with scissors and notice main cavity. Have the lateral buds cavities? Do
they communicate with the main chamber? The texture of the sponge re-
sembles felt. Cause of this? Draw the group with above details expressed.

16. Place a portion of the wall (single thickness) in a solid watch glass
of Borax Carmine. Cover it and leave an hour. [While waiting. conduct ex-
periments 17-19 and then return.] Wash out in 70¢, 5-10 minutes. Then five
minutes each in 95 7—100 z—turpentine—and place in a drop of Balsam on a
slide, inner wall uppermost, cover and examine. Most superficially come the
endodermal cells, which in life are like collared monads. By focussing a lit-
tle deeper the spicules come in view, and deeper yet the irregular cells of the
mesoderm. Certain of these are very large—spherical and deeply stained.
These are either eggs (one large cell) or spermatozoa (a mass of cells). Draw
these details.

17. Select another portion of the wall, spread it out on a dry slide, inner
wall uppermost, and allow to dry. When perfectly dry, examine for spicules,
50-60".

18. Place a few pieces in a watch crystal of K-O-H, and heat gently
over an alcohol lamp. Pipette the residuum upon a slide, cover and examine,
50-60". Compare with dried specimen. Express the results of the last two

66 INVERTEBRATE ZOOLOGY.

experiments by drawings showing (1) Isolated spicules, (2) Relation of spicules
to each other. Include in the examination the spicules about the osculum.

19. Mount a small piece temporarily in 70¢. Add a drop of HCl at
edge of cover and watch result through microscope. Of what are the spi-
cules composed ?

Type II.—A Sycon Sponge.

90. Study a specimen (or small group) as in 1. Do not cut open with
scissors, but use a razor or asharp scalpel. Divide the sponge longitudinally,
and make a few cross sections of one longitudinal half. Examine all these
in the watch crystal. If you succeed in obtaining a very thin cross section,
make a temporary mount of it and examine, 60°. Note the thick walls, the
narrow central chamber and the pores in its walls. What do these signify ?
Does an examination of the sections of the walls solve this problem? Have
these pores any regular order? Note the palisade of large spicules about the
osculum.

91. Repeat 4 for spicules.

992, Study of prepared sections. Method and introduction. The walls
of this specimen are too thick to be mounted whole as in 2, and we must
resort to microtome sections. The two most useful are longitudinal and
transverse sections.

[For this purpose specimens are prepared as follows :

(1) Borax Carmine, 36 hours and thus stained in toto.

(2) Washed out in ‘‘ acidulated alcohol,” i. e. 70% + a few drops of HCl, un-
til bright scarlet, 3-5 minutes.

(3) 95 %—3-6 hours.

(4) 100 ¢%—8-6 hours.

(5) Turpentine—s8-6 hours.
(6) In paraffine, in oven, 1-2 hours and imbedded. |

Consider the form of the specimen and answer the following :—Will one
sponge yield more transverse or more longitudinal sections ? Which set will
vary more among themselves? Will all longitudinal sections include the
lumen? Longitudinal sections lying in the plane of a radius of a transverse
section are termed radial, those not including a radius, but merely parallel to
a tangential plane, are termed tangential. How many of each sort? Are
all radial sections the same? Are all tangential sections? If the longitudi-
nal axis of a specimen curves, how will that complicate the sections? What
sort of specimens should be selected for sectioning ?

INVERTEBRATE ZOOLOGY. 67

93. Study of a transverse section. Note the radial canals, characteris-
tic of the type, the outlines of which form a symmetrical rosette. The canals
are lined with endoderm cells of the same sort as those lining the main
chambers of the Ascon. Between these are the spicules—broken by the knife
in cutting. Can you detect any regular arrangement of these? Notice the
long spicules forming an external cone capping each canal. What is the shape
of acanal? Is it possible to tell from cross-sections alone? Why do some of
the canals appear more or less filled up with cells ?

94, Study of a longitudinal section. How do the canals appear in this?
Are they differently shaped in the middle and at the ends of the section.
Explain this.

After the above study, construct a series of diagrams representing the com-
plete structure of the sponge. giving the relation of canals and partitions,
arrangement of spicules, etc. These are not to be copies of the sections.
Sections are generally imperfect, cut obliquely, torn, etc. A diagram should
be without imperfections and should combine the result of all different modes
of observation, and thus be a graphic method of representing one’s knowl-
edge. In constructing these diagrams let each student select the view and
devices which seem to her the best means of expressing the structure. Thus
for instance: a perfect cross-section, with whole spicules, occupying such
positions as will illustrate their plan of arrangement. The effect is height-
ened if delicate colors be used to represent the different parts [cf. Dendy’s
plates in Quarterly Journal for 1893]. A radial chamber, drawn as a solid
body, and covered with spicules in regular arrangement, would express the
shape well and explain the different planes seen in the sections.

Additional study of sponges :—

95, Spicules may be isolated from a piece of silicious sponge by teasing
or by K-O-H [cf. 4]. The shapes may be studied and their composition
tested by HCl. This should not be added to a specimen in K-O-H, as the two
reagents will counteract each other. If the fresh water sponge, Spongilla,
be macerated in K—O-H, especially in the case of specimens collected during
the autumn, gemmules may be isolated as well as the spicules.

96. Skeleton of a horn sponge. With a sharp razor make several very
thin sections of a perfectly dry piece of bathing sponge and drop them into
a watch crystal of turpentine for five minutes. Select the thinnest one and
transfer it to a slide, spreading it out in a drop of turpentine. This structure.
which is the part we use, is merely the skeleton of the sponge animal, the cel-
lular portions having been removed by maceration or boiling. This skeleton

68 INVERTEBRATE ZOOLOGY.

is neither silicious nor calcareous, but composed of closely interwoven threads
of chitin (same material as horn, silk, etc). Draw a small area of this under
a high power to show the relation of the threads to each other. This speci-
men may be permanently mounted by removing the cover, wiping away the
excess of turpentine and adding a drop of Canada Balsam.

Type Ill.—Hydra.

The Hydra is the only fresh water representative of the group. It is found
in quiet pools, clinging to submerged vegetation. It is tubular or vase-shaped
with 6-8 long thread-like tentacles hanging from the free end. There are two
principle forms distinguished by their colors—the brown one, Hydra fusca,
and the green one, Hydra viridis.

97. Field work. Search for specimens in stagnant water abounding
in aquatic plants. Hydras average 14 inch in length and may be sometimes
seen attached to submerged leaves and stems, their long tentacles streaming
in the water. They are easily seen in an aquarium, but to find them in a nat-
ural pool is much more difficult. The best plan is to collect a handful of aqua-
tic plants, place them in a jar filled with clear water and hold it up to the
light. The observation should not be too hasty. for hydras are extremely
sensitive and contract at once when so roughly handled. One should there-
fore wait a few minutes and allow them to expand. Repeat this test several
times and in different localities.

98. Study of external form. Place a hydra ina watch crystal of water
and observe with a dissecting microscope. Make outline drawings of several
shapes and positions. Place under the low power of the compound micro-
scope, and study the structure of the tentacles, body wall, etc. Make a
sketch, using an outline (one of those just made), and fill in what you see. It
is better to draw one tentacle and a little portion of the body-wall minutely
and leave the rest in outline.

99, Study of life habits. Keep two or three specimens for several
weeks in a large beaker, placed where it can be frequently watched. Feed
with minute fresh water Crustacea (Cyclops, etc). The results of this experi-
ment depend largely upon luck and continual observation. If fortunate, one
may observe (1) the prey caught by the tentacles and conveyed to the mouth
lying between them ; (2) the growth of new individuals from the sides of the
older ones ; (3) the subsequent separation of the offspring as an independent
hydra, etc.

INVERTEBRATE ZOOLOGY. 69

30. [This difficult experiment is placed here only as one which may be
done, and should be attempted only by patient investigators, who are prepared
for repeated failures.| Trembly, a French zoélogist. in 1744, cut living hydras
in two and found that under favorable conditions each piece would grow
again into a perfect hydra. He even cut one into several pieces and found the
larger portions were capable of becoming complete animals.

This experiment is easy to attempt. but results are hard to obtain. Cut
several hydras in different ways—transverse, longitudinally, etc.. and keep
the portions in a beaker of clear water. Scissors may be used for this, but a
sharp razor is better.

31. Study of a cross-section. To killa hydra in an expanded condition,
place in a watch crystal with a very little water. and suddenly deluge the ani-
mal while expanded with a test tube full of hot alcoholic corrosive sublimate
[70¢ + HgCl,]. Allow it to stand a few minutes until cool and then place in
a large amount of pure 707%, which should be changed once after a few hours.
Such a specimen may be treated as the Sycon Sponge in 22 and sectioned.
In the section, notice the two layers of cells, ectoderm and endoderm, separa-
ted by a definite line, the supporting lamella. Sections of different animals
and of the same animal at different planes, show different points, as follows :

a) Ova, large cells with amoeboid processes, crowded in between the two
layers, but belonging to the ectoderm. Sections at about the middle of the
body show this.

b) Testes, a conical mass of cells, belonging to the ectodermic layer, form-
ing a protuberance. Mostly in the upper portion of the vase-shaped body.

c) Cross-section of a tentacle. Notice the few huge endoderm cells which
form a lining and enclose a minute central lumen continuous with the gas-
trocoele.

d) Nettle cells, (nematocysts). These may be found anywhere, even in endo-
derm, but are most common at the ends of the tentacles. They are large,
oval capsules, semi-transparent, and much more refractive than the surround-
ing tissue.

Type IV.—Campanularia.

32. Make preliminary examination of material in a dish of 70%. No-
tice the two forms of polyp, each enclosed in a transparent cup. Select and
cut off with scissors one or two good branches for mounting. These should
include specimens of both sorts of polyps; and, if possible, in different stages

6

70 INVERTEBRATE ZOOLOGY.

and conditions—expanded, contracted, buds, empty cups, etc. Branches, the
members of which lie approximately in one plane, are the best for this pur-
pose.

33. Mark out on a sheet of white paper a series of rings the size of
watch crystals, and designate as follows :

Borax

ow
S
xQ

100 %.
Carmine.

mee

Place watch crystals on these and fill with the corresponding liquids. Use
a solid watch-glass for the 1004 and keep it covered. Drop the branches se-
lected into the borax carmine and let them stay 5-10 minutes, until deeply
stained. Then transfer successively to the different watch crystals, 4-5 min-
utes ineach. Use a needle for this, but do not break or prick the specimens.
From the turpentine spread out the branch on a slide in a small drop of bal-
sam. Cover and examine. The living protoplasmic portion is colored pink
and consists of the polyps and irregular connecting stems between them, run-
ning through the centre of the branches. The whole is invested by a trans-
parent chitinous skeleton, the perisarc, which encloses the stems and expands
into a cup about each polyp. Study details as follows :—

a) A feeding polyp or Hydranth. The body is divided by a constriction
into a terminal portion (manubriwm) which bears the tentacles, and an ex-
panded basal portion. How many tentacles are there? Is the number con-
stant? What can be seen upon these with the high power? The basal por-
tion is hollow, containing the gastrocoele, or gastro-vascular cavity. Around
the hydranth is an expanded cup, the hydrotheca. Can a polyp entirely re-
tract into this? In this species the hydrotheca has the shape of a bell (cam-
panula), hence the name. Just below the polyp the perisarc is divided into
rings or joints. What is the probable use of them? Is their number con-
stant? Does it bear any relation to the age or size of the polp?

b) A reproductive polyp or Blastostyle. This is merely the stalk which
bears round medusa-buds ; it may be considered a reduced polyp, elongated in
shape, and without mouth or tentacles. It is surrounded by a cup, the
Gonotheca. Compare with a hydrotheca.

c) Medusa-buds. These are produced as buds from the sides of the Blasto-
style. Which of these are the most mature? In what direction does growth

INVERTEBRATE ZOOLOGY. 71

progress? Study the oldest of these buds. Can you find traces of medusa
structure? [cf. 35].

34. Express by drawing the results obtained. As such may be sug-
gested: 1)asketch of an entire branch, only a few times enlarged, drawn
from dissecting microscope. 2) An enlarged figure of each sort of polyp.
Make this a perfect and symmetrical diagram, taking the details from several
if necessary. Thus one specimen may have the best manubrium, another may
show good tentacles, another a perfect hydrotheca, etc. 3) Drawing of de-
tails as seen with a high power. Thus a portion of an enlarged tentacle,
showing nettle cells, or a bit of body wall seen in ‘ optical section” i. e.
focused to show the thickness of a lateral wall: the specimen is thus cut by
the focal plane of the microscope. Such detailed drawings as these may
be drawn beside (2) and connected by dotted lines with the corresponding
part.

35, Study of a free medusa. These are caught in the open ocean with
a tow net and may often be found in preserved specimens of tow. In this
species they are of the size of pin-heads, disc-shaped and bordered by a fringe
of tentacles. Search for them as follows: Place a watch crystal of 707 on
stage of dissecting microscope. Pipette into this a drop of thick tow. This
dilution will serve to isolate the forms, which may then be sorted over with a
dissecting needle, looking continually through the lens. In case of fresh liy-
ing tow, use sea-water instead of 70¢ for the dilution. When one is found, it
may be stained and mounted as in 33, but handled with a pipette instead
of a needle. In this, reduce to a minimum the amount of liquid transferred
with the specimen. In case a specimen becomes lost, place the crystal upon
the stage of the dissecting microscope and search as at first. In a well
mounted specimen there may be seen :—(1) the manubrium, (2) four radiating
canals, (38) four genital masses lying wpon the canals, (4) the tentacles with
otocysts at the base of some of them.

OTHER STUDIES OF HYDROZOAN FORMS.

o6. Pennaria is a common form and shows many important differences
from the foregoing. Prepare and study in the same way and note, 1) the
perisarc does not grow up over the polyps, but stops short at their bases, leav-
ing them unprotected. 2) The medusa-buds do not grow upon a blastostyle,
but at the bases of the ordinary polyps, which are of but one kind, all hy-
dranths. 3) These buds do not become free, but remain as reduced gono-
phores, producing the genital products in the place of origin. The gonophores

72 INVERTEBRATE ZOOLOGY.

are bisexual and produce eggs or spermatazoa. These unite in the water and
develop into a polyp which may develop asexually into another colony. 4)
There are also minor differences in the shape and arrangement of the tenta-
cles, the nettle cells, the stem, ete.

37. Thamnocnidia (or Clava). These are solitary polyps, although gen-
erally associated in clumps. Each polyp bears at its base very numerous
medusa-buds or gonophores in racemose clusters. The male gonophores libe-
rate the spermatozoa, which escape into the water; but the female gonophores
retain the eggs which are fertilized and develop in situ, and leave it in the
form of minute polyps, which pass out backwards, drawing their tentacles
after them. Cross-fertilization is insured because a given polyp produces
gonophores of only one sex; the polyp, although asexual, is thus often termed
male or female. Thamnocnidia is too large for mounting entire. It may be
studied in a watch crystal, and separate gonophore-clusters mounted.

Clava may be mounted by cutting little strips of cardboard, soaking them
a few minutes in turpentine and placing them in the balsam with the speci-
men, and in such a way that the weight of the cover glass is sustained by
them.

SCYPHOZOA and CTENOPHORA.

Members of these classes are peculiarly difficult of preservation and can be
studied well only at the sea-shore. The hard parts of coral can be studied in
any good collection. The spicules of Aleyonaria (octocoralla) are microscopic,
and may be isolated as follows :—

38. Place in a test-tube a small portion of the Polyparium of any
Aleyonarian. Cover with K-O-H and boil until there is left a residue in the
bottom of the tube. Axial portions or other hard masses may be removed
and the residue handled by decantation. Allow the residue to settle and then
pour off the excess of K-O-H. Fill up with water, shake gently, let it settle
and again decant the excess. Repeat the washing with water two or three
times and then wash successively in 704, 954, 100%, and finally ‘turpentine,
leaving the material in the last three for some hours each. Pipette a drop of
the material thus prepared upon a slide, drain off the excess of turpentine
with a cloth or blotting-paper, add balsam, cover and examine. Different
species will yield different results. [This experiment will furnish material
sufficient for an entire class. |

INVERTEBRATE ZOOLOGY. 73
Type V.—Turbellaria (any fresh-water form.)

39. Field-work. Select for investigation a small pool or ditch of water.
The water must be stagnant or slightly flowing, but pure and without foul
odors. It should contain an abundance of green water plants and perhaps a
little floating green slime as indications of the purity of the water. Use for
collecting a net of cheese-cloth and a glass jar. Place the jar in the net and
fill it with clear water by reaching out from the margin towards the center of
the pool. Let the jar down and pass the empty net slowly back and forth
through the water, taking care when turning the net not to reverse it. The
minute animals contained in the water will thus be caught in the net and may
be transferred to the jar by carefully reversing the net over the mouth of the
jar and washing it gently. Hold the jar up to the light and examine. Collect
material in the same manner from different depths and portions of the pool
and finally scoop up a few of the sticks and leaves from the bottom and add
a bit of scum and a piece of some aquatic plant. In this way the jar may be
made to contain a sample of the different environments the pool affords. To
study the gauna of each environment, the different collections must be kept
apart and labelled. In this particular case the material from the bottom will
be the most important. Examine the material thus collected and look for
soft, very contractile, flat worms, which vary from a short oval to a long
worm-like form. They vary in size from almost microscopic dimensions to
1.5 and in color from slate grey to brown, yellow or green. In an undis-
turbed aquarium they frequently crawl in an inverted position along the
under side of the surface of the water, after the manner of snails.

40. Finda Turbellarian in the material collected in 39, transfer it to
a watch crystal with a pipette or glass tube and study with a dissecting mi-
croscope. Notice its change of form and its mode of motion. It moves by
muscular contraction aided by cilia, which cover its entire surface. These
can be well seen on an edge when the specimen is under examination with the
high powers [41 e]. In one group (Dendrocoela) the intestine is dendritic, i. e.
branched like the limbs of a tree, and shows very conspicuously even with the
single lens. In others it is a straight rod and not very noticeable (Rhabdo-
coela). Notice also several other organs, usually dendritic, on the sides of the
alimentary canal. These are the reproductive and yolk glands. The mouth
is on the under side, about central, and rather difficult to see. Two pigment
flecks at the anterior end serve as eyes.

41. General anatomy. Several common species of fresh water Turbel-
laria (mostly Rhabdocoela) are so transparent that the internal organs may be

44 INVERTEBRATE ZOOLOGY.

well studied in the living animal by compressing it slightly. Cut from a piece
of cardboard a frame the size of the cover-glass and 2-3™" wide. Soak it in
water and apply it to the center of a slide. Place a living specimen in this
with a drop of water, cover and examine. By this means the animal will be
slightly flattened and its motions circumscribed. Observe the following—100".

a. Alimentary canal. The mouth is near the centre of the under side and
is best seen by placing an animal ventral side up, although it may be generally
made out by focusing through the body. It is circular and may be seen to
open and close during the muscular contortions of the animal. The mouth is
connected with the main alimentary tract by a cylindrical pharynx, which in
a flattened animal may lie unsymmetrically upon the side. The canal itself
is rather opaque, owing to its contents, and may be variously shaped [40].

b. Reproductive system. Turbellaria are hermaphroditic and the organs of
both sexes are very complicated and often dendritic. Two sets of branching
organs may be seen at the sides terminating in finger-like lobes. Of these,
the thickest lobes, showing white by reflected light, and visible with the sim-
ple lens, are the yolk glands. The other set, similar, but more delicate, forms
the testes. The uterus. also branched, is very thin walled and almost invisi-
ble, but is generally easily located by the large conspicuous eggs which it con-
tains. If these are numerous, they will be seen to be arranged in rows which
mark the disposal of the uterine tubules.

c. Nervous system. The pigment eyes may be seen to rest upon an opaque
mass from which pass four branches, two anteriorly and two posteriorly.
The main mass forms the brain, and the branches are the four principal nerve
cords. The anterior cords may be followed into the very extensile anterior
end, where they resolve themselves into a brush-like mass of minute nerves,
which render this extremity a very sensitive tactile organ. The posterior
cords run down the sides of the body and divide into minute nerves. There
is often a commissure just posterior to the pharynx connecting the two poste-
rior cords.

d. Nephridial system. This is an important system, but hard to make out
in a living specimen. Four branching tubes, two anterior and two posterior,
collect the liquid excreta from the body parenchyma. On each side the ante-
rior and posterior tube join and form thus two lateral ducts which run into
the pharynx near the mouth.

e. Cilia. These are visible only at the edge, but it must be concluded that
they cover the entire surface, from the fact that they are visible along the
entire edge and at every edge that may be formed by chance foldings and

INVERTEBRATE ZOOLOGY. 75

changes of shape. If the animal is sufficiently quiet, a high power (500°) may
be used.

492, Preserving and mounting. Turbellaria are among the most diffi-
cult animals to preserve. It is almost impossible to prevent their complete
contraction upon the application of the customary fixing reagents, and even
if this be effected, they are apt to disintegrate or dissolve. If the preserva-
tion has been successful, there are many obstacles to success in staining. The
integument and body parenchyma stain as deeply as the organs, and thus the
internal parts, although well stained, are completely hidden. The following
methods are an attempt to overcome these obstacles :—

a. Fixing and preserving. Use for this Lang's fluid, prepared as follows :

Weber si guna t na cree bie cotcls a Sil. wee abs 100 parts.
Sodimiriy Cn OniG eh aes wach eae eee Oe ee
EA CELI CHA CIO Nein stele oe cho he aie ee ok 5-8
CORrOsive SUDIUMAlet es -lees eee. ecole
TANITA rt asc ee ea eee em eer LA TNE a

Apply it cold, poured suddenly over the animal when expanded. Let it re-
main in the fluid 14-1 hour, then in 3807, 50%, 2-3 hours each and finally in
70 % for preservation.

b. Staining. A successfully stained specimen for mounting iz toto should
have the separate systems faintly outlined, ‘the integument and parenchyma
being as nearly colorless and transparent as possible. To effect this, two
methods may be used—either to stain very slightly, or to stain deeply and
afterwards extract the superfluous color with acid. For the first, use ORTH’S
Lithium Carmine, Alum Cochineal, or EHRLICH’s Haematoxylin, a few drops
in a beaker full of 707%—extremely dilute. Let it remain 1-3 weeks, taking it
out from time to time for examination. For the second, use Lithium or Borax
Carmine, diluted about one-half, stain 10-15 min. and extract the extra color
with acid alcohol (i. e 70% + several drops of 10% HCl.). Watch this and
check the action of the acid when necessary, by placing in clear 70%. All
specimens for toto mounting must be flattened before applying the stain.
This may be done with a slide and cover, placing the whole under the lens
and pressing with a needle handle. <A large specimen, if well hardened, may
bear the weight of a slide. Specimens which are to be prepared for section-
ing may be diffusely stained without much subsequent withdrawal, and of
course should not be flattened. Living specimens, stained in neutral Bis-
marck brown, as with Infusoria, show clearly defined nephridia and nerve-
cords.

76 INVERTEBRATE ZOOLOGY.

43. Drawing in this case a diagram is the only practical form of draw-
ing. In all such cases as in that of 40 and 41, where one deals with a rap-
idly moving object, observation must consist of a long series of rapidly ac-
quired facts and equally rapid conclusions, and the drawing must be a graphic
representation of the facts observed. <A piece of drawing paper should be at
the side of the student, and each conclusion, when clearly formulated, should
be sketched in. The details of the diagram should not be all obtained from
one procedure ; the general shape is best gained by the simple lens ; a success-
ful preparation also [42] is of great assistance in comparison with microscopic
observation on the living animal.

Type VI.—Distomum (0r allied genus),

44, Trematodes, or fluke-worms, are as adults endoparasites in Verte-
brates, living in the cavities of the alimentary canal and its accessory organs,
the lungs, the gall ducts of the liver, the bladder, etc. They are almost uni-
versal in frogs and may be found as follows: Place a live frog under a small
bell jar and add a small piece of cotton saturated with chloroform. In a few
minutes the frog will be dead and may be removed for dissection. Place it
upon its back and with the scissors make a median longitudinal incision on
the ventral side, the entire length of the body. The shoulder girdle will be
met with in the thoracic region and must be also cut through. Find and ex-
amine the following internal organs :

a. Lungs. A pair of dark grey sacks lying above the liver on the sides of
the oesophagus. If they are empty they will be small, wrinkled and very
elastic ; if inflated they are large and conspicuous. Cut these off at their
base and place in a Stender dish of water for examination.

b. Urinary bladder. This lies at the posterior end of the incision, close to
the bones of the hip girdle. Look for the large, dark green cloaca, or termi-
nus of the intestine. Upon this may be seen several wrinkled folds of trans-
parent membrane, which spreads over quite a large area, when drawn out
with the forceps. This is the bladder. Trematodes may frequently be seen
in this, when spread out, owing to the transparency of its walls. Carefully
remove it, cutting it away from below, and place it in the dish with the lungs.

c. Alimentary canal. This is to be cut through above the stomach and

just above the cloaca, and removed entire by cutting away all of its connect-
ing membranes,

INVERTEBRATE ZOOLOGY. TU

These organs may now be searched. Place them one at a time in the small
glass dissecting pans on the stage of the dissecting microscope. open them
with the scissors, pinning them out when necessary. The entire alimentary
canal shonld be opened and its contents washed out, after which the canal
itself may be removed. Each organ has its own separate species of Trema-
tode, each of which have their peculiarities of investigation, and may be sep-
arately treated. Any one of these will do for study alive, but the one from
the lung may be taken as the type, and is the only one to be mounted.

45. Study of living Trematodes. (From frog.)

45. a. Lung form. Study this at first superficially in a watch crystal
and search for the two sucking discs characteristic of the genus. Then flat-
ten it by compression (it will probably bear treatment between two slides, and
perhaps some pressure added to this) and observe by transmitted light, first
with the simple lens and then with the low power of the compound micro-
scope. The most conspicuous organ is the uterus, filled with eggs. By a lit-
tle added pressure the eggs may be made to escape like a fine dust from the
genital opening. Locate this and examine eggs with the high power. The
anatomy in general is similar to that of Turbellaria [41].

45. b. The form from the alimentary canal. This is a very small oval
worm scarcely 2™™ in length. It is to be placed on a slide in a drop of water,
covered by a cover glass and studied with transmitted light. It is very satis-
factory to study on account of its small size and transparency. |cf. 41.]

45. c. The form from the bladder. This is opaque and cylindrical and
should be studied only in a watch crystal of water, attached if possible in its
natural attitude to a piece of the bladder-wall. Its ventral sucker is enor-
mous, projecting and cup-shaped, and is used for attachment. The portion
of the body anterior to this is very extensile and used as a tactile organ.
Compare and homologize the body regions and suckers of this animal with
those of the other species.

46. To mount a Trematode use the lung-form, fixing and staining as di-
rected in 42. Forrapid work, the use of weak borax-carmine is recommended,
followed by the acid alcohol treatment. In this, as in most small Distoma, the
testes are not dendritic. but are in the form of compact, rounded masses,
which stain deeply, and which, with the similar shaped ovary, form three
conspicuous masses posterior to the ventral sucker.

47. Larval Stages (—Asexual generations). Trematodes exhibit a com-
plicated alternation of generations, the other forms being parasites of aquatic

78 INVERTEBRATE ZOOLOGY.

animals, generally molluscs, and by a variety of expedients become transferred
to their final Vertebrate host. Collect a few of the common brown snails found
in ponds, break off the shell and examine the soft brownish mass which fills the
apex of the whorl. This mass is the liver and may be frequently found filled
with minute worms of different shapes. These may be transferred to a slide
with a pipette, mounted in a drop of water, covered and examined. The
three main forms are the sporocyst, redia and cercaria, which are very easily
distinguished and may be identified by referring to any text book. (CLAUS or
LANG.) Good permanent mounts are difficult, but may be done by applying
the different reagents drop by drop upon the slide, and removing the liquids
as desired, by inclining the slide and using a cloth or piece of blotting paper.
The entire process should be performed under a dissecting lens. A quantity
of the material may also be prepared at one time by careful decantation
[cf. 38], or perhaps an entire snail’s liver may be stained and the separate par-
asites subsequently dissected out.

Type Vil.—Taenia Crassicollis.

48. This is the common Tape-worm of the domestic cat, and is found in
the adult state in the intestines of that animal. To obtain specimens of this,
the intestines of all the cats used in the Vertebrate course are opened with
scissors and examined. They are seldom found in kittens, and are found in
about one out of three adults, there being often 4-6 entire worms in one host.

[lf convenient, one or two cats will be examined before the class at this
point, that the Taeniae may be seen in their environment. |

AQ. Superficial examination. Keep the specimen in a glass dissecting
pan, covered with 707 and observe :—

(a) The Scolex or “head.” This is the blunt point at the anterior end of
the animal, and is not in the shape of a rounded knob with attenuated neck,
as in most tape-worms. [cf.specimens of T. Saginata, etc. Also notice specific
name, Crassicollis.| Notice on the Scolex form rounded depressions, the
suckers, also a double row of chitinous hooks. Place the specimen for a mo-
ment upon a slide and bring the Scolex under 50-60". Notice the shape and
arrangement of the hooks.

(b) The Proglottids or ‘‘ links.” These resemble the segments of segmented
worms, but in reality are not, but are continually produced by vegetative
growth from near the base of the Scolex. The proglottids at the free (poste-
rior) end are the oldest and are sexually mature, while towards the scolex they

INVERTEBRATE ZOOLOGY. 79

grow smaller and less mature, the youngest being at the anterior end where
they may be seen dividing off and becoming more distinct. If all the pro-
glottids are broken from the scolex in a living tape-worm, the scolex alone re-
maining, it will in a few weeks produce a second series of proglottids.
On the edge of each proglottid may be seen a slight projection containing
a minute opening. This is the genital papilla and is used both for fer-
tilization and for the passage of the eggs. The papillae of some tape-worms
occur all on one side, but here they generally alternate, those of adjacent
*links being on opposite sides. In other species each proglottid is double, hav-
ing genital papillae on each edge.

50. Preparation of a proglottid. Select a mature link and cut it off
with scissors, leaving portions of adjacent links attached. Place it between
two slides, hold it up to the light and apply gradually increasing pressure
with the thumbs and forefingers. Watch this procedure carefully and stop at
the first indication of cracking. A well preserved link will usually sustain
as much pressure as may be applied by this means. As it becomes gradually
more transparent, the different organs will become distinct, the most con-
spicuous being the dendritic wterus filled with eggs. A dark line passing
from this out to the genital papilla indicates the oviduct and the male vas
deferens. The staining and mounting should follow the rules given in 42.

51. General anatomy of proglottids. The anatomical relationships of
parts are complicated and difficult to follow. In general the organs are simi-
lar to those of Trematodes, altered in shape to fit the rectangular outline of
the links, and the lateral position of the genital opening. The successive
links represent different stages of development, and hence in order to fully
understand the parts, several preparations should be made and compared.

(a) An ‘“‘immature” link. This refers to one taken about in the middle of
the animal, where the links are generally much broader than long. In such a
link the male organs are mature, while all the female organs, ovary, yolk
glands, etc., are small but distinct. Notice : testes, many small round masses
giving a mottled appearance to the lateral regions of the links ; vas deferens,
a slightly wavy tube leading to the genital papilla and ending in a small
pouch containing the cirrhus or organ of copulation ; ovary, an oval mass,
central in position, but on the posterior margin; from this last an oviduct
runs parallel to the vas deferens, and opens at the genital papilla: yolk glands,
lying along the posterior edge of the ovary; uterus, a tubular sack extending
from the ovary through the center in an anterior direction—this may or may
not bear small lateral branches ; nephridia, a pair of tubes running along the
lateral margin and united in each segment by a transverse tube.

80 INVERTEBRATE ZOOLOGY.

(b) A mature link. Here the eggs have formed, and filled the uterus, which
has branched enormously in order to accommodate them. The other organs,
except the oviduct, have become suppressed.

52. Cross-section of a Proglottid. This is to be prepared for the class as
in the case of the Sycon sponge [22], cut on the microtome and mounted. In
this observe: (a) The body-parenchyma, filling all the spaces between the
organs and leaving no coelom. The parenchyma is crossed by muscular fibres
which in general run parallel with the body-wall, and surround the organs.
Upon the outside of the parenchyma there is a thin transparent cuficula. (b)
Two lateral excretory canals cut across. The section may show a portion of
a transverse canal connecting the lateral tubes. (c) The eggs which mark the
position of the uterus. The double contour shows the presence of a thick
shell. If the eggs are developed, three pairs of delicate chitinous hooks may
may be seen in some, appearing as parallel lines. Such forms are the ‘‘six-
hooked embryoes,” ready to penetrate the walls of the stomach of their first
host and encyst themselves in the liver. These hooks are provisional organs
and not the same as the definite hooks of the Scolex.

53. The encysted Scolex (=Cysticercus). This is the Taenia as it develops
from the egg, and encysts itself in the body of its first host. The cysticercus
of this species is found in mice and must be sought for as follows :—Open a
mouse by a median ventral incision and either pin it open on the table or bend
it gently backwards over the finger. Find the /iver, a dark red mass consist-
ing of several lobules, lying just beneath the diaphragm a little on the right
side. Look over the surface of all the lobes for a large round whitish spot
shading off into the red. This spot should be nearly as large as a pencil end
and indicates the presence of an oval cyst the size of a pea, imbedded in the
liver substance. When such a cyst is found it should be carefully dissected
out, and opened under the lens by asimall incision at about the middle. Search
carefully for a rounded scolex, with hooks and suckers, resembling the scolex
of the adult Taenia. When found, carefully remove the superfluous portion
of the cyst, preserve the scolex as directed in 42a, and when thoroughly pre-
served, flatten slightly and stain with borax carmine as in the case of
hydroids [33].

Type VIlI.—A Rotifer (especially gen. Rotifer or Brachionus).

These are microscopic forms found in fresh water, about the size of large
ciliate Infusoria and when first discovered, classified with them. They are in

reality minute Metazoa with development from eggs. Recently through the

INVERTEBRATE ZOOLOGY. 81

examination of a tropical rotifer, Trochosphaera, which appears to be a modi-
fied Trochozoén, the group has gained in interest, as in it we have probably
lineal descendants of that ancient form, differentiated and modified through
adaptation to special environments.

54, Rotifers are best studied alive in a drop of water, as in the case of
Infusoria. Search in different places in an aquarium, particularly in the slime
on the under side of leaves and among the material at the bottom. They are
distinguished by an elongated tail, composed generally of joints, and by the
characteristic ‘‘ wheel apparatus.” which they unfold at the anterior end, and
often suddenly retract. Obtain a good specimen, preferably one whose mo-
tion is circumscribed by debris, and observe the following points :—(a) The
three body regions ; retractile portion or head, main body region or thorax,
and tail or foot. (b) The ‘‘ wheels :” these are in the typical forms a pair of
lobes covered with cilia which move in such a way as to give to the lobes the
appearance of revolving wheels. These are probably modifications of the
prae-oral band or trochus of the ancestral form. (c) Notice the stream of
particles drawn into the body between the wheels: follow it inwards and
notice the masticatory apparatus, a set of chitinous teeth continually moving
back and forth. The other organs of the body are difficult to distinguish and
may be studied by the help of text books [cf. VoGr u. JunG. pp. 424-445].
The sexes are separate, but the males are very small and comparatively rare,
appearing only at certain times in the year. The females lay two sorts of
eges. The first or swmmer eggs are parthenogenetic, soft shelled, and of two
sizes, the larger one producing females and the smaller ones males. The sec-
ond sort, the winter eggs, are the product of copulation: they have hard
shells generally marked with curious and complex sculptures, and produce
females alone. In some species (Brachionus, etc.,) the eggs, when laid, remain
clinging to the body of the parent, while in others they are deposited in rows
on water plants.

55. Gastrotricha. These area small group of animals, allied to Rotifers
and occurring with them. They have a fish-like form, but are depressed and
have a broad ciliated double stripe of cilia along the ventral surface, making
them appear like hypotrochous Infusoria. They may be considered as modifi-
cations of the Trochozoén, but in a different direction from that taken by the
Rotifers. In these the trochus has disappeared, the ventral stripe alone per-
sisting as the locomotive organ.

82 INVERTEBRATE ZOOLOGY.

Type IX.—Ascaris lumbricoides.
Ascaris mystax.

The two above species belong to the group of parasitic Nematodes known as
‘**pin-worms” and occurring in the stomach and intestines of Vertebrates.
The first named is a large form (20-40°™) occurring in man and the pig, and is
generally selected as the type of the group. As this is rather difficult to ob-
tain, it may be supplemented by A. Mystax, common in the cat, and very sim-
ilar to the first, but smaller (4-10°™).

56. External characteristics (A. Mystax). For this, use both microscopes
according to judgment, the lowest powers first.* Notice the following :—The
anterior end is provided with two lateral wing-like processes, giving the whole
the appearance of the fluke of an anchor. This is characteristic of the
species. The mouth is situated at the point, surrounded by three oral papil-
lae. The posterior end is gently curved in the female, convolute in the male.
In both, the anal orifice is a transverse slit, just ventral to the tip. It serves
also in the male as a reproductive outlet and is furnished with two minute
bristles, or spiculae. Anterior to the anus upon the ventral side there are
15-20 papillae. In the female the oviducts open by a single orifice, situated in
the mid-ventral line at about the anterior third of the body.

57. Internal Anatomy. The species Lumbricoides is large and easily dis-
sected, but impracticable to use in quantity. A. Mystaa may be handled in a
small dissecting pan, as in the case of the grasshopper, Type XVIII; or a
watch crystal may be used, coated with paraffine, and the parts pinned out
with fine insect pins. The body should be opened by a median ventral incis-
ion, and the body-wall spread apart. The alimentary canal is a straight tube
extending through the center ; it is divisible into an oesophagus, somewhat
swollen in its posterior portion, and a chyle-intestine. The rectal portion re-
ceives in the male the vasa deferentia and may be here termed cloaca. The
reproductive organs consist in both sexes of a pair of convoluted tubules,
folded back and forth and several times the length of the body. The free end
of each is closed, and in this portion the germ-cells are formed. The nephridia
are contained in two lateral ridges on the body-wall, which run the entire
length of the body. They end by transverse ducts near the anterior end,

* Hereafter, directions for simple microscopic procedures will not be given, as the student
should now be sufficiently skilled in the use of the instrument to be able to exercise inde-
pendent judgment in each case. An exception to this will be made under Type XVIII, which
is to be used as a preliminary study.

INVERTEBRATE ZOOLOGY. 83

which unite and open by a median ventral pore. The nervous system consists
of an oesophageal ring and a pair of longitudinal cords, dorsal and ventral,
which are borne by ridges similar to those which contain the nephridia, but
smaller. Both nephridia and nervous cords are best seen in a cross-section
[58]. Circulatory and respiratory organs fail.

58. Cross-section of Ascaris (preferably lumbricoides). Look first for
four projections of the body-wall, 90° apart and corresponding to the four
ridges just mentioned. These will serve to orient the section. The two lat-
eral ridges are much the largest, and contain each a cross-section of a delicate
tube, the nephridium. The ridges for the nervous cords support rather than
contain them, and thus appear somewhat cup-shaped, bearing a whitish re-
fractive solid substance, the nervous cord. The body-wall consists principally
of an outer transparent cuticula and a thick mass of irregular muscle-cells,
some of which encroach upon the coelom. <A fibrous layer between the two
and directly underlying the cuticula may be looked upon as a sort of hypo-
dermis, originally cellular, but showing in the adult only a few scattered
nuclei. The alimentary canal occupies typically a median position and con-
sists of a single layer of somewhat irregular epithelial cells, with a thin inner
cuticula. A muscular layer fails. The remaining tubules. lying in the coe-
lom, belong to the reproductive system and present different aspects in size
and cellular formations according to sex, period of development, and regions
cut by the plane of the section. In sections of the mature uterus, eggs may
frequently be met with, provided with a transparent shell showing a double
contour. The embryoes develop to a certain stage in the body of the parent,
and may be seen in the early segmentation stages. or in the blastula or gas-
trula form.

59. Additional studies of Nematodes. There are several other forms of
considerable general importance, which should be investigated as occasion
offers.

a. ‘* Vinegar-eel” (Anguillula aceti). Hold a vinegar-cruet up to the light
and look for exceedingly minute worms, frequently so numerous as to give
the impression of some optical peculiarity in the liquid which causes it to
shimmer. These are minute nematodes, feeding upon the fungus which
converts the cider into vinegar, and called the ‘‘mother.” All specimens of
vinegar do not contain these nematodes, but if a specimen containing a bit of
the fungus be taken, one is almost certain to find them. Pipette a little of
such vinegar into a watch crystal and observe with the dissecting microscope.
Single nematodes may be transferred to a slide, covered and examined with
higher powers.

84 INVERTEBRATE ZOOLOGY.

b. Trichina spiralis. This is the famous parasite found in pork, causing
in those who eat it a dangerous muscular disease. It was the cause assigned
by Germany for prohibiting during several years the importation of American
pork. The parasite exists in infected meat in the encysted form, the separate
cysts appearing as minute white dots, somewhat oval in form, occurring be-
tween the separate fibres. Specimens of infected meat may often be obtained
from Governmental experiment stations or from private investigators. Tease
out a few scraps of the meat under the lens and look for the cysts. They are
better seen by reflected light. To study them they are best flattened gently,
and stained with borax carmine [42 b]. They should remain in the turpentine
until quite transparent, when the worms will be seen coiled up in the cysts.

c. Nematode parasites in the frog, etc. Interesting parasitic forms may
be found in the lungs and intestines of the frogs. and generally appear while
searching for Trematodes [44]. The black lung-form is especially interesting,
being an hermaphroditic parasitic form, which alternates with a bi-sexual
form living in damp earth. This phenomenon is known as heterogony. (cf.
the text-books under Rhabdonema nigrovenosum and Rhabditis nigrovenosa. )
A little nematode found in the frog’s intestine is very transparent and conve-
nient for microscopic study.

Type X.—Lumbricus Terrestris.

60. Study of a living specimen. Place a large earth-worm in a saucer
of water, and notice the following :—It elongates and contracts in length.
What sort of muscles cause this? What is the course of their fibres? It
changes its caliber at the same time. What sort of muscles do this? What
difference in shape of the two ends? Which is anterior? Which end is the
more sensitive? Where must the nervous system be best developed? At
which end are the sense-organs best developed in all bilateral animals? Why?
Has the animal distinct dorsal, ventral and lateral aspects? Notice along the
sides, rows of minute bristles, especially prominent posteriorly. If the ani-
mal be drawn between the fingers, there is more resistance in one direction
than another. Can that be explained by the direction of the bristles? Notice
the cingulum, a fleshy girdle surrounding the body. Is this nearer the ante-
rior or the posterior end? Notice the body-rings or segments. These are
true segments and not reduplicated abdomens as in the tape-worm.

61. Killing and preserving.

a. Killing. While dying, earth-worms are apt to contract and throw them-
selves into such tight coils that dissection isimpossible. To obviate this, place

INVERTEBRATE ZOOLOGY. 85

a worm in a saucer of water and introduce alcohol very slowly until the de-
sired result be obtained. It answers nearly as well and is often more conve-
nient to throw them alive into 25-307. They will writhe and coil themselves
at first, but ultimately the majority will straighten out quite well.

b. Preserving. If the specimens are to be used for dissection, the body
cavity should be opened by a few slits along the mid-dorsal line, and the spec-
imen returned to the 307 4-6 hours and then in 707% for permanent preserva-
tion. If immediate dissection is desired, open the animal as soon as killed,
dissect under 30% and place in 70% at the end of the first day’s work. For
staining and sectioning, a more complicated course is necessary. The alimen-
tary canal is normally filled with earth, which renders sectioning impossible.
To get rid of this, keep a living animal for several days in a box of damp
coffee-grounds until the earth is entirely replaced. Fine saw-dust is also
used, but is not as good. Fair results may often be obtained by simply starv-
ing an earth-worm in clear water, changing it daily. In sections taken from
such animals, the cells of the alimentary canal will be abnormally contracted.
If none of the above methods are convenient, very small earth-worms may
be used, thus reducing the quantity of earth to a minimum. When ready,
the animal is to be killed as above, but removed as soon as possible, and cut
into several pieces, which are to be separately preserved in some good fixative
with subsequent treatment with alcohol. Either of the following are espec-
ially recommended :—

I. Aqueous corrosive sublimate 2-6 hours.
Water; running, or large quantity often changed, 14-14 h.
304% alcohol 4-8 h.
70% aleohol—permanently.
II. Kleinenberg’s Picro-sulphuric acid, 2-6 h.
70 Z—This should be changed repeatedly at intervals of 4-12 h., until it
remains colorless.
The original location of each piece should be known, and may be designated
by cutting the pieces into different lengths, or by preserving them in separate
bottles, carefully labelled.

62. General Anatony.

(a) Eaternal characteristics. Notice again on the dead animal the parts
mentioned in 60, the segments, bristles, cingulum, etc. At the anterior end
is a partial segment, projecting over the mouth. This is the prostomiwm, or
lip, and is not counted as a segment. Count the segments from this past the

a

86 INVERTEBRATE ZOOLOGY.

clitellum ; what segments does the clitellum include? Posterior to this the
segments vary in number. Notice upon the ventral side, anterior to the cli-
tellum, a pair of slit-like openings, surrounded by fleshy lips. These are the
external openings of the vasa deferentia. Upon what segment are these ? Look
for a pair of minute openings upon the segment just anterior to this. These
are the openings of the oviducts, and are visible only during the period of
oviposition. Between the 9th and 10th, and between the 10th and 11th seg-
ments, are two pairs of minute openings leading into spermathecae, or recep-
tacles for the spermatic fluid. These are visible only during the pairing sea-
son. Each segment possesses a pair of nephridia, which open on the ventral
side, at the anterior border of each segment, in front of the little pits for the
bristles. These are at all times difficult to see. The anus is at the posterior
extremity of the body.

(b) Internal anatomy. The dissection should be under alcohol in a glass
dissecting pan, as in the case of Type XVIII. The animal may be cut in two
about 10-15 segments posterior to the clitellum, and only the anterior portion
studied, as the posterior segments are all alike. An incision should be made
with the scissors along the mid-dorsal line, and the animal carefully pinned
out. The segments are separated by connective tissue partitions, the dissepi-
ments, which are attached to the integument. These prevent one from spread-
ing of the body-walls properly, and should be cut from the integument with
a scalpel. When this is done, make a superficial examination of the organs in
situ, without farther dissection. Notice:—The alimentary canal with its
divisions, running through the center.—The dorsal blood vessel, lying upon it,
filled with red blood—a series of 5-6 pairs of enlarged lateral blood vessels,
the so-called ‘‘ hearts,” also red, which are given off from the dorsal vessel.—
Between these, 2-3 pairs of little orange bodies, the calciferous or oesophageal
glands.—The spermatic vesicle, a large mass of whitish lobes, three on each
side.—The spermothecae, two pairs of little round sacs, just anterior to the
testes and lying on the ventral wall.—The brain, or swpra-oesophageal gang-
lion, a duinb-bell shaped whitish mass at the extreme anterior end, and lying
upon the anterior enlargement of the alimentary canal.—The nephridia, little
coiled tubes lying on the sides of the body, in each segment. These are best
seen in the posterior portion. Notice farther that the dissepiments are com-
plete partitions, dividing the segments into separate coeloms, and allowing
continuous organs, as the alimentary canal, to perforate them, as in the dia-
phragm of mammals.

After this general survey, the systems are to be carefully dissected, one at
a time, cutting merely the connective tissue connections, studying the shape

INVERTEBRATE ZOOLOGY. 87

and location of each part, and the relations of parts to each other. In this,
reference may be made to the following tabulated view of the systems. For
details, refer to the different text books.

63. Anatomical Synopsis.
[In this, the order is that of preparation; the numbers refer to the seg-
ments. |
1. ALIMENTARY CANAL.

Mouth. With prostomium.

Pharynx. A large oval mass, attached by muscular fibres to the
body-wall.

Oesophagus. A long, narrow tube, surrounded by the hearts
(5-18), and bearing the—

Oesophageal, or calciferous glands. These are three pairs of lat-
eral diverticula of the oesophagus, containing calcareous
bodies (11-18).

Crop (Ingluvies). An oval shaped dilatation of the posterior end
of the oesophagus. Its walls are comparatively thin (14-16).

Gizzard, or stomach (Ventriculus). A round mass with thick,
muscular walls (17-18).

Intestine. A large tube of equal caliber throughout, with thin
walls disposed laterally in folds. A portion of the dorsal
wall is invaginated, forming the Typ/hlosole. (see cross-section)
19—to end.

Liver mass (chloragogue cells). A diffused mass of yellow-brown
pyriform cells, covering the intestine dorsally and giving it
its yellow color. (Seen in cross-section ; also by isolating the
cells by scraping the canal very gently, and mounting tem-
porarily.)

2. REPRODUCTIVE System (Hermaphroditic).
(a) Male.

Vesicula Seminalis (spermatic vesicle). A large rectangular, yel-
low-white organ, lying beneath and at the sides of the ali-
mentary canal (about 10-11), varying in extent in different
stages of development. Divided across into two portions ;
the anterior expanded laterally into two paired lobes, and the
posterior into one. These lobes increase in size posteriorly,
and when well developed are recurved upon the main portion.

88 INVERTEBRATE ZOOLOGY.

Testes. These are beneath the spermatic vesicle and are exposed
by removing the dorsal wall of the vesicle and taking out its
contents. They may then be seen as two pairs of little solid
white organs, lying upon the sides of the nerve cord (10, 11).
Their cells pass by some unknown way into the spermatic
vesicle, in which they develop.

Vasa deferentia. Slender tubes, beginning with two pairs of
funnel-shaped openings just posterior to the testes (10, 11).
Upon each side the two tubes unite into one (12), thus form-
ing two lateral vasa deferentia, which open externally (15).
The funnels collect the ripe spermatozoa which escape from
the spermatic vesicle by an orifice communicating with the
coelom.

(b) Female.

Spermothecae. Two pairs of spherical sacs, used to contain the
spermatic fluid of another individual, received during pair-
ing. The eggs are fertilized by this fluid and not by that of
the same animal. They lie upon the ventral wall (9, 10) and
open separately between the segments (9-10) (10-11).

Ovaries. A pair of very small organs, lying upon the ventral
wall (18) on each side of the nerve cord. The mature eggs
break loose and float about in the coelomic cavity until col-
lected by the oviducts. The ovaries are scarcely visible ex-
cept when mature.

Oviducts. Two little tubes, which begin as funnel-shaped open-
ings in the dissepiment between (18) and (14). These collect
the eggs and open externally in (14).

38. CIRCULATORY SYSTEM.

The blood is red (colored plasma, white corpuscles) and thus the ves-
sels are easily traced. It is a closed system, entirely separate from
the coelom.

Longitudinal vessels. These are five in number. (1) median dor-
sal, (2) median ventral, (3) sub-neural, (4) and (5) a pair of lat-
eral neural vessels. The blood flows in an anterior direction
in (1), posteriorily in the others.

INVERTEBRATE ZOOLOGY. 89

Commissural vessels. The lateral stems communicate by vessels
which pass around the body. In the genital region, five pairs
of pulsating commissures, the ‘‘ hearts,” pass from the dor-
sal to the ventral vessel. In the intestinal region, commis-
sures unite the dorsal with the sub-neural. Other communi-
cations are through anastomoses of capillary terminations.

Lateral supply vessels. The body-wall, intestines and other
organs are supplied by vessels passing from the main trunks.
These form capillary net-works about the parts supplied.

4. EXCRETORY SYSTEM.

Every segment except the first three possesses a pair of lateral Ne-
phridia (segmental organs). They are the largest in the segments
just posterior to the reproductive organs, and are best studied there.
Each nephridium is a convoluted tube, having a free end, which
floats in the coelomic cavity. This has a ciliated funnel-shaped
opening and collects excretory material from the coelom. The tube
passes through the dissepiment and empties externally in the suc-
ceeding segment. Each tube may be divided into a transparent, a
glandular, and a terminal portion.

5. NERVOUS SYSTEM.

This consists of a brain or supra-oesophageal ganglion, lying upon the
pharynx, and a ventral cord possessing ganglionic enlargements in
each segment. The brain sends out anterior nerves to the prosto-
mium and unites with the ventral chain by a pair of lateral com-
missures. These send out nerves to the pharyngeal region. From
the cord pass out lateral nerves, a ganglionic pair from each gang-
lion, and an interganglionic pair from the intervals between them.

64. Study of a cross-section. Mount a microtome section cut from a
piece prepared as in 61, and try to interpret the parts shown by means of the
anatomical knowledge gained by the dissection. The parts especially brought
out will be the typhlosole, the longitudinal blood-vessels, the chloragogue
cells, and the nervous cord. The study of the body-walls and the muscular
layers is only to be accomplished by sections. If the plane of section passes
through the bristles (setae), examine and compare with 65.

65. Study of parapodia of a Polychaete (Nereis). This is the common
clam-worm found at low tide in mud-flats. Notice in an entire specimen the
lateral expansions of each segment which bear the setae, These are the par-

90 INVERTEBRATE ZOOLOGY.

apodia. Cut off a single parapodium with the scissors and examine in a
watch crystal. It may afterwards be flattened and mounted. The parapo-
dium is double, consisting of dorsal and ventral portions. On the dorsal half
notice :—A flat triangular piece, the gill—connected with this a slender pro-
cess, the cirrus—a fleshy lobe bearing several bristles (setae), and a single me-
dian spine (aciculum). Compare the ventral half. What part is lacking?

Type XI.—Cambarus sp ?*

(Astacus or other cray-fish will do as well. Homarus may be used for class
demonstrations. )

66. External anatomy. Cray-fish may be killed by placing them under
a bell-jar and adding a bit of cotton soaked with chloroform ; or by immer-
sion for a few moments in strong alcohol. In the latter case they should be
removed as soon as dead, to prevent the shrinking of the tissues which would
occur if the alcohol were allowed to penetrate the interior. The specimens
may be examined in the air, but should be dropped into water at least once
an hour, that the internal parts may remain moist. A jar containing one or
two living specimens should be placed on each table for study of the use
of external parts. The parts may be studied in the following order :

I. GENERAL ForRM.

Bilateral symmetry, with dorsal, ventral, two lateral, anterior and poste-
rior aspects. What other types have been bilateral? Is the distine-
tion between dorsal and ventral more or less in Lumbricus ? in As-
caris 2? Which shows higher development ?

Skeleton. This is an exo-skeleton, consisting of a chitinous cuticula, rein-
forced by mineral salts. Test the carapace with a drop of HCl.
What does it prove? Notice the structure of the joints (arthra), del-
icate membranes extend between the hard pieces and allow free mo-
tion. Notice how the hard pieces overlap when parts are contracted.
cf. dorsal pieces of abdomen. Compare the whole with mediaeval
armor.

*The arrangement of Crustacean types is the reverse of the usual order and is rather that
of convenience in obtaining material, than that of logical sequence. It is supposed that
Type XI will be studied at the opening of the college year (Sept.—Oct.), and is followed by
forms that may be kept alive in laboratory aquaria, and by marine forms that must be
studied in alcohol. The natural order, showing the derivation from polychaetous Annelids,
would be the following :—(1) Polychaete. (2) Branchipus. (8) Cyclops. (4) Porcellio. (5)
Cambarus.

INVERTEBRATE ZOOLOGY. 91

Metamerism. Possesses true segments (somites or metameres). Are the
segments similar or dissimilar? What is the advantage of meta-
meric differentiation? Is it greater or less here than in Lumbricus ?
Which is the higher ?

Body-regions (—segment-complexes). Three body-regions as in grass-
hopper ; first two fused, making (1) a cephalo-thorax, composed of
immovable segments, and covered dorsally by a single shield-like
piece, the dorsal carapace, and (2) an abdomen of moveable seg-
ments.

Cephalo-thorax. A transverse suture (cervical suture) near the middle.
This marks division between head and thorax. A median, anterior
process, the rostrwm. The sides of the carapace are free and form
covering pieces for the gills (branchiostegites). Break off one and
notice the gills underneath ; also the lateral body-wall, delicate and
white, behind them. The gill chamber is thus external. Ventrally,
notice the appendages, five pairs of legs, of which the first is for
attack and defense, and not used in walking. The genital openings
are at the basal joints of a certain pair of legs, differing in the two
sexes. Compare different specimens. Where are they in the male °
in the female? Find the mouth and note the large number of ap-
pendages about it, used partly as jaws and partly to hold or taste the
food.

Abdomen. Consists of seven segments, each with a large dorsal plate,
tergite, and a very narrow ventral piece, the sternite. The first five
segments bear small legs used for swimming (pleopods). The ap-
pendages of the sixth segment are expanded, and form, with the
seventh segment, which is without appendages, a five lobed tail.
How is this tail used? In the spring the females attach the eggs and
young to the pleopods and protect them with the tail. The seventh
or final segment bears the ans.

II. APPENDAGES.

There are nineteen pairs of appendages, each of which represents a somite.
Of these pairs, thirteen belong to the thorax and six to the abdomen. The
cephalo-thorax thus consists of thirteen somites and the abdomen of seven
(the last without appendages), giving a total of twenty somites. They are

92 INVERTEBRATE ZOOLOGY.

best studied in the following order. Remove them from one side only, leav-
ing those of the other in their natural order for comparison.

1. A typical pleopod. Select this from the 8d—5th abdominal somite. It
consists of a basal piece, protopodite, double in this case ; and of two
terminal branches, the outer or exopodite, and inner or endopodite.
This is considered a typical appendage, of which the others may be
considered modifications.

2. The sixth pleopod. This is flattened to assist in the formation of the
tail. One of the terminal branches is double. Which is it?

3. The first and second pleopods. These are different in the two sexes.
In the male they are large and peculiarly twisted, and capable of
approximation to form a copulatory tube for the conveyance of the
spermatozoa. In the female they are both normal in shape, but the
first are very small.

4. A walking leg (periopod). Select the next to the last leg. Separate
it from the body, taking care to remove it entire. It consists of
seven joints, to the first of which are attached a plumose gill and a
flat gill paddle, epipodite or flabellum. The joints are named in
order: (1) Coxopodite. (2) Basipodite. (8) Ischiopodite. (4) Mero-
podite. (5) Carpopodite. (6) Propodite. (7) Dactylopodite. Select
the first leg beyond the large claw. Notice that it ends in a claw
also i. e. is chelate (chela=claw). Does this result from the addition
of an eighth piece? Compare with the former one and explain.
Compare with the large claw. Is the differencein size the only one ?
cf. living animal for difference in use. Compare with the typical
form (a pleopod). The leg may be explained by the suppression
of one of the terminal branches and subdivision of the other into
joints. To find out which branch is suppressed, compare with the
next.

5. The third mawxilliped. This is the segment next anterior to the large
chelae. (The segments will now be taken in order, going towards
the anterior end.) This is intermediate between a jaw and a foot,
as its name denotes. Has it an epipodite? <A gill? Do you recog-
nize the leg part? Has it the same number of joints as the others ?
Do you find the branch which was not developed in the true legs?
How would you then describe a periopod ?

INVERTEBRATE ZOOLOGY. 93

6. The second and first maxillipeds. Remove these in order and com-
pare with the third. Which terminal branch shows a gradual reduc-
tion? Which one shows increase? Can you homologize the parts of
the endopodite in each? Look for a gill and an epodite in each.
Notice in the first, the flattened maxillary processes, projecting in-
wards. There are two of these, corresponding to the two divisions
of the protopodite.

7. The second maxilla. Do you recognize in this an exopodite? An
endopodite? An epipodite? With what is the epipodite fused?
How many maxillary processes are there? Can you explain them
with reference to those of the preceding ?

8. The first maxilla. Which of the two terminal branches fails here ?
Can you homologize the maxillary processes ?

9. The mandible. This consists of a hard jaw with toothed edges and a
palpus. What typical part does each represent? Compare with
last.

10. The second antennae. These consist of a protopodite and the two
terminal branches. Which one is developed into the long, tactile
portion? Notice at the base, the conspicuous opening of the nephrid-
ial organ, the so-called ‘‘ green gland,” situated in the center of a
raised papilla.

11. The first antennae (antennulae). These are biramous. Upon one
of the branches are situated tufts of club-shaped hairs, probably
olfactory. Examine both branches with the microscope and find out
which one possesses them. Examine the base of these antennae for
the auditory organs, little cavities open to the air, into which the
animal pushes sand-grains to serve as otoliths.

12. The eyes. These have been supposed to have the value of append-
ages, being movably articulated with the body, but they develop as
fixed parts and become secondarily free.

The number and relationships of appendages and somites in Crustacea may
be expressed by formulae. An xX denotes that a part is present: R signifies
that a part is rudimentary; — that it fails. Simple abbreviations may be
used for the names of the appendages, Roman numerals for the somites of the

94 INVERTEBRATE ZOOLOGY.

cephalo-thorax, Arabic for the abdomen. The following is the formula for
Cambarus :—

No. of Somite. Name of Appendage. Basal Piece. Exopodite. Endopodite.
I Ant, x x x
II Ant, 4 R x
JOU Md x = x
IV WB, x = x
Vv Mx, Xx Xx x
WAL Mxp, x x x
VII Mxp, NK x x
VII Mxp, x x x
IX Leg ,(Chelae) x = x
x Leg, x = x
al Lee Gemale cy. 4% es x
XIt Leg, x = x
n. op.
XII Leg, Sey x we x
é 1, ) modifi
iB Pl! eee Xx x as
16 Pare x x x
17 Pl x x x
18 Pie x x x
19 Pl, (caudal fin) >< x x
20 — — —

10H, <(Gameresy

Remove the branchiostegite from the side upon which the appendages have
not been disturbed, and examine the delicate plumose gills. For this, immer-
sion in water or weak alcohol will be necessary. There are three classes of
gills, named according to their point of attachment.

(1) Podobranchiae, attached to the basal joints of the legs.

(2) Arthrobranchiae, attached to the delicate membrane between the skel-
etal pieces ; of these there are two sorts, anterior and posterior.

(3) Pleurobranchiae, attached to the lateral body-wall (Plewron).

Gills may occur on every segment between VI-XIII, and each segment may
have four, one podobranchia, two arthrobranchiae (anterior and posterior) and
one pleurobranchia. Thus typically a complete equipment would number
4832, Actually, however, a portion of these fail, the resulting arrange-

INVERTEBRATE ZOOLOGY. 95

ment being constant in a given species. but varying in different species. Fill
in the following blanks with the formula for Cambarus, indicating the pres-
ence of a well-developed gill by an x, a rudiment by R, and adding the
epipodites.

GILL FORMULA FOR CAMBARUS.

Somite. Podo. Ant. Arth. Post. Arth. Pleuro. Epip. Total.
VI

XU
yaa
Total eS ee eae

67. Dissection of internal organs. Cambarus is dissected from the dor-
sal side as in other Arthropods. For an animal of this size, a small tin dis-
secting pan should be used, and the specimen covered with weak alcohol. A
lens may be removed from the dissecting microscope and held in the fingers
over the object, when minute observation is required. If necessary, a small
and complicated part may be removed to a small glass dissecting pan, or
watch crystal, and examined microscopically.

The specimen should first be taken in the hand and the dorsal carapace care-
fully removed in small pieces, taking great care not to harm the subjacent
organs. Then the abdominal tergites may be cut through at the sides and
removed. When this is completed, pin the specimen in the pan.

(The student should now be ready to identify the different organs himself. at least in a
simple form like Cambarus, and hence general rules for identification of parts and order of
dissection will be substituted for the usual anatomical description. This method will be

followed as far as possible in the rest of the book, excepting, of course, Type XVIII, which
is designed as a preliminary study. ]

Asa general rule, the alimentary canal should first be sought, and when-
ever it is coiled or in any way obscures other parts, may be dissected away
from its connections and laid aside. In this case, however, the delicate cen-
tral organ of the circulatory system, the ‘* heart,” lies above the intestine, and
should first be studied, The circulation can only be successfully demonstra-

96 INVERTEBRATE ZOOLOGY.

ted in an artificially injected specimen, and for this purpose a large form, like
the lobster, should be used. With the alimentary canal occur various diges-
tive glands, one of which, the liver, is very constant in its occurrence. It is
to be expected below the stomach, and is generally brownish or greenish in
color and voluminous in size. Its connection with the alimentary canal should
be traced, after which it may be removed with a portion of the canal. The
stomach is peculiar in this animal and possesses a set of chitinous teeth,
worked by external muscles. This should be carefully examined. In a bi-
sexual form, as in this case, the sex should be determined by external indica-
tions if possible, and the internal reproductive organs should then be sought.
As essential parts of this, one may expect a germ gland, ovary or testis, and a
tube, generally long, and often coiled, through which the germ cells may pass
to the exterior. In the male this tube is proportionally small, and is termed
vas deferens, while in the female it is often large, and termed oviduct. If a
portion of it is enlarged to serve as a receptacle for the retention of eggs or
embryoes, it is called the wlerus. Accessory organs are common and may be
always expected, in the male, glands to secrete a quid medium in which to
suspend the germ cells, and in the female, glands for yolk, shell-material, al-
bumen, etc., besides receptacles for spermatozoa, etc.

Nephridia, either as separate tubes or united into a mass, may be expected
in any location, and in this case are in the form of the green gland, at the
base of the second Antennae. The nervous system is similar to those of the
earth-worm and grasshopper. The muscular system should be studied in con-
nection with the skeleton, whether external or internal. The mechanism of
a few joints, or of a few characteristic body-movements, will prove sufficient
in the general study of a type.

68. Histological study. To obtain and preserve material for the study of
cell structure, an animal should be killed by chloroform, and dissected either
in the air or under water. The parts to be sectioned should be selected, cut out
as rapidly as possible, and preserved by the method recommended for pieces of
earth-worms, 61 b, land II. The pieces selected should be small, and sepa-
rated as much as possible to allow the ready access of the reagents to all
parts. After preservation, the parts may be kept in small bottles of 70% well
labelled. For sectioning, a piece may be stained in toto, the principal being
the same as in the staining of hydroids, the amount of time being regulated
by the size and density of the piece. From the turpentine the piece is put
into melted paraffine (in the paraffine oven) and imbedded when completely
infiltrated, It is impossible to assign exact times for the different procedures,

INVERTEBRATE ZOOLOGY. 97

but the following may be taken as a mean estimate. Specimens are not
harmed by exceeding the time in the stain or in 707, but the higher alcohols
and the turpentine render them hard and brittle.

Preparing an object in toto for microtome sections.

1. A specimen, preserved as above, is taken from the bottle of 70% and
placed in borax carmine—twenty-four hours.

2. Take from the stain and place in ‘“‘ acid 70%” i. e. 70% + a few drops
of HCl. Watch the piece and see it turn from a dull maroon to a
bright scarlet. The change should be moderately slow (5-10 min-
utes). A too rapid change denotes an excess of acid, a too gradual
change denotes too little. This should be remedied in either case.
The piece should remain until it is thoroughly penetrated by the
acid alcohol (10-20 minutes).

oo

Place in clean 70 % (2-6 hours).
4. 95% alcohol (6-12 hours).

5. 100% alcohol (4-8 hours).

6. Turpentine (4-8 hours).

7. Melted paraffine (2-4 hours).
8. Imbed.

Small Stender dishes are the best to use for the work of the fluids. The
100 % should be kept in a tightly corked bottle. Bottles are often conveniently
used for carrying about when changes are to be made out of laboratory hours.
A preparation made in this way is amply sufficient for an entire class, and
may be made by one person, the students taking turn in thus preparing the
class specimens. Sections through the ‘‘ liver” (better hepato-pancreas) or
through the intestine are very instructive and simple in structure.

Type Xil.—Porcellio sp?

69. Collecting and preserving. Thisis the common ‘‘ sow-bug” or ‘* damp
‘pug,’ a terrestrial Crustacean found in damp shady woods beneath stones, and
is often met with under bricks and boards in barns and cellars. Simple im-
mersion in 707% is sufficient to kill and preserve them for the study of the ex-
ternal parts, and each student before the approach of cold weather should

98 INVERTEBRATE ZOOLOGY.

collect a bottle full of such specimens (8-10) to serve as a supply. For inter-
nal anatomy they should be dissected in a fresh state, also prepared for the
microtome and sectioned in various planes. As with insects, their hard chit-
inous exo-skeleton forms a barrier to the penetration of the various preserva-
tives, to overcome which, various means have been adopted, as follows :—

1. The use of hot fixing reagents. These are to be heated in a test tube
and poured suddenly over the animal while alive. Perhaps the best
for this purpose is hot alcoholic corrosive sublimate. This should
remain 20-40 min., then washed out in 70 7%.

2. The selection of specimens which have just moulted and in which the
chitin is soft and tender. These are also best preserved with hot
reagents,

3. Punch or prick a hole through the exo-skeleton in a region not after-
wards to be used for sectioning. A living animal may be cut in two
with a sharp razor and the two parts instantly dropped into the
fixative.

Asin the case of preservation, staining also presents serious difficulties.
To overcome these, use an alcoholic stain of a high grade (Borax Carmine
may be made as high as 707%); also continne the immersion for a long time
(several days or weeks if necessary). This will not hurt the specimen if the
stain contains a high percentage of alcohol. Sections may be cut from an un-
stained object and stained on the slide, by the method known as ‘‘slide stain-
ing.” For this, cover the slide with an albumen fixative, rubbing it in
well with the finger. After this, heat in the usual way, until the paraffine is
melted, and then apply the usual reagents in the reverse order (4-5 minutes
each), turpentine—100 7—95 7—70 7, etc., until the specimen reaches the grade
of the desired stain. Apply the stain to the object and then pass it up again
through the same succession as far as the turpentine. Then wipe the slide
carefully, except the area covered by the specimen, which may be well drained
but must not become dry. Add a drop of Balsam and cover as usual. The
application of the different reagents is best performed by immersing the en-
tire slide successively in jars containing the desired reagents, or in the case
of single sections, the reagents may be pipetted on the slide, drop by drop,
and successively wiped away, held in the hand or rested from time to time on
some convenient support. All the different stains may be applied in this way,
haematoxylin being especially recommended.

INVERTEBRATE ZOOLOGY. 99

70. Fxternal Anatomy. Use for this specimens killed by simple immer-
sion in strong alcohol. Remove them, and spread them out on a glass slide
upon the stage of a dissecting microscope, allowing them to dry. The larger
external parts are best studied in this way, while the smaller appendages,
maxillae, etc., may be mounted temporarily in a drop of water for details.
Look over several specimens and distinguish the following: (1) Females car-
rying young. These have a brood-sack formed by broad plates attached to
the inner side of the first five pairs of legs. In this may be found eggs and
young in all stages. Such females possess a median birth-opening between
the fifth and sixth pairs of legs, while the lateral genital openings are obso-
lete. (2) Females without brood-sack. These lack the appendages upon the
legs, also the median birth-opening, but possess lateral genital openings at the
bases of the fifth pair of legs. Females change from one of the above forms
to the other by a moult. (3) Males. These possess a median organ of copula-
tion at the juncture of thorax and abdomen. This folds backwards with the
gills, but is generally easily distinguished by its darker color. A pair of gen-
ital openings lie at its base.

1. General body-form. The body is depressed, i. e. flattened derso-ven-
trally. The thoracic somites are free, and not united into a carapace as in
Type XI. On the dorsal side note :—The head ; this consists of the true head
of five somites + the first thoracic somite: the long antennae (—second):
look carefully on the inner side of the base of these for the very rudimentary
first pair ; the eyes, a facetted surface on each side. Seven free thoracic so-
mites ; the first is concave anteriorly and receives the head, the last concave
posteriorly, for the small abdomen. The abdomen, six separate pieces, large
lateral processes on the second—fourth, the sixth representing the sixth and
seventh somites fused. cf. Type XI.

2. The appendages. These may be separated with forceps or sharp needle,
the larger ones studied dry and the smaller ones mounted temporarily in
water. Those of the thorax and abdomen should be studied first, upon the
entire specimen, For the parts of the head, remove this piece by cutting it
through from the dorsal side. The parts here are delicate and may be best
handled by placing the entire piece in a watch crystal and covering it with
water. Make a detailed study of the separate parts, as in the case of the pre-
vious Type, and draw each. Refer to the following formula :

100 INVERTEBRATE ZOOLOGY.

Somites. Appendages.

( Be) Ant, Rudimentary.

| II | Ant, Large.
se)
Sale | = Ma
se r &

IV | a IMExs

(ste SAV | Mx,

(Sale) Mxp Lamellate, folded over the others.

| VII ner =|)

| VIII L,
4 | IX Ibi + With brood lamellae in female.
o 4
a | x IU

XI Wye 1)

| XII Dies

| XIII I

( 14 15d Les)

| 15 PS |

| Endopodite serves as gill.

a | 16 Leda:
g |} "7 Pl Expodite large, containing air chambers.
ro) ‘
= | 5 Serves also as protection for the true gill.
a 18 Pie) J)

| 19 ) a Pl, Without gill, forming part of tail.

eae)
[20 2 —— Central tail piece, fused with 19.

71. Study of a cross-section. The internal anatomy of Porcellio is very
similar to that of Type XI, and need not receive especial attention. A general
idea of the relationship of the different parts may be obtained from a cross-
section prepared as in 69. The section should be taken through the thorax
and will serve as a type to illustrate the relationship of systems in Arthropods
in general. In the center will be the alimentary canal ; above this will be the

INVERTEBRATE ZOOLOGY. 101

dorsal blood vessel, and beneath it the nervous cord. The tubules and glands
of the reproductive system will lie symmetrically upon the sides. If the sec-
tion be well cut, the relation between the muscular masses and the exo-skele-
tal plates will be beautifully shown. The external chitin is difficult to cut
and is apt to crack into little pieces, some of which will be carried upon the
edge of the knife across the section. This may be obviated by the use of the
following reagent :

Gum mastic,

Absolute alcohol,

Ether,

Collodion,

Take about equal parts of these, put the gum mastic in the alcohol, and allow it to
dissolve as much as it will ; then add the other ingredients.

This is to be applied to the flat section-surface of the paraffine block, and
allowed to dry. The microtome screw is then turned and the section cut off
in the usual way. The liquid forms a thin film over the section which holds
the pieces of chitin in their natural place.

72. Preliminary study of the next three types. These represent three
groups of minute Crustacea, having an average size of a small pin-head, and
constituting the bulk of the material collected with the tow net, whether in
marine or fresh water. The type specimens used here are fresh water forms
and are collected in the same way as the Turbellaria, Type V. They often
develop in quantity in the laboratory aquaria through the chance introduction
of a few adult individuals, or from’ eggs brought in with the mud. Place the
material containing these in a shallow crystallizing dish and set over a black
surface. Look for small, rapidly moving animals, which may be distinguished
by shape and mode of motion.

1. Somewhat elongated forms, body tapering behind into a tail. The
females often possess a pair of egg-sacs half as large as the body,
depending from the sides of the abdomen. They move by quick,
darting motions, often progressing 3-4 inches by a single propulsion.
They are thus very difficult of capture and are best taken by a long
glass tube, Into which a quantity of water may be suddenly drawn.
These animals are Copepods, of which the commonest form is Cy-
clops, Type XIII.

2. Oval forms, somewhat flattened laterally, i. e. compressed. (cf. de-
scription of Porcellio, 70, 1.). The body is covered by a pair of lat-
eral shells which leave the head free. They are propelled by the sec-
ond pair of antennae, which are enormously developed and used as

102 INVERTEBRATE ZOOLOGY.

oars. Hence their motion consists of short rapid jerks. There are
many common species of this group; Branchiopoda, Sub-order Cla-
docera, any one of which may be taken as a type. The form de-
scribed below is Simocephalus, a common form, larger than the ay-
erage, and should be secured if possible.

3. Perfectly oval forms, entirely covered by large lateral shells, which
include the head. These are the smallest of all and seek the bottom
and sides of the glass, progressing by a steady, rolling motion,
caused by the projection of minute legs from between the edges of
the shells. They are Ostracods, mostly belonging to the genus Cy-
pris, which is taken as Type XV. The large species, variegated with
green and white, should be taken, if possible.

The methods of investigation are similar in all three types. The two first
are best studied alive, as they are so nearly transparent that the internal
organs are readily seen. Examination in a watch-crystal under the dissecting
lens will give the general body form, the use of the appendages, mode of mo-
tion, etc., while they may be placed under the compound microscope by using
slide and cover. They may be quieted by chloroform, which may be applied
in drops, or by holding near them a bit of blotting paper, saturated with it.
Warm Perenyi’s fluid poured over a group of Cypris, placed in a watch-crystal
will cause them to die with the shells beautifully expanded. They may be
preserved and sectioned as in 69. A mass of them may be handled at once by
filtering the water containing them through a bit of muslin, after which they
should be tied up in the muslin by a thread, and the bag and all subjected to
the action of the different reagents. They must be removed from the bag to
be placed in the paraffine oven and may be imbedded by pouring the paraffine
containing them into a watch-crystal previously smeared with glycerine. The
position of the separate individuals may be seen through the translucent mass
and individuals that lie in a favorable position may be cut out in a cubic or
oblong piece, which may then be melted upon the end of a large block and
cut in the usual way. They are rather difficult to stain in toto. Slide stain-
ing gives good results.

Type XIII.—Cyclops sp?

73. External anatomy. The body is covered dorsally by a carapace
which includes the head (five somites) and one leg-bearing thoracic somite.
Then follow four free thoracic somites, each bearing a pair of legs. The long
tapering abdomen consists of five somites (first two fused in female) and ends

INVERTEBRATE ZOOLOGY. 103

in a fork (furea) tipped with long plumose bristles. In the center of the an-
terior end of the carapace is the eye, a fleck of pigment which gives sensation
of light and possibly of color. This eye gave the animal its name, but it is
really double, as is seen by its shape. There are two pairs of antennae, of
which the first bears tufts of olfactory hairs. It is transformed in the male
into a clasping organ, used during pairing. The legs consist of a double basal
piece and two branches, each consisting of flattened joints. There are no
gills. The formula for somites and appendages is as follows.

Body Regions. — Somites. Appendages.
I Ant, (Clasping in male.)
II Ant,
Head III | Md
IV | Mx,
V Mx,
Wire) De
| VII Ly
Thorax {+ VIII Ir
IX ibe
( x ID (Reduced in size.)
11
| 12
Abdomen — + 13 poo es
14
ite —— (With anus and furca.)

74. Internal anatomy. The alimentary canal is a straight tube in the
median line with but little differentiation of parts. Anus in fifth abdominal
segment. No accessory organs. During life the canal oscillates continually
back and forth, stirring the fluid in the body cavity and thus functionally re-
placing a circulatory system, which fails entirely. There is no special respira-
tory system. The reproductive organs differ in appearance during different

104 INVERTEBRATE ZOOLOGY.

periods and should be studied in connection with the life history and develop-
ment.

75, Development. This should be studied by arranging a small aquarium
in a Stender dish or tumbler. Place in the bottom a layer of pond mud
and introduce a bit of some green alga. Cyclops will multiply in this readily
and very rapidly, and all stages may be found. For special study, individ-
uals, pairs, etc., must be isolated and kept ina smaller dish. Investigate the
following points :—

(a) Males. These are much smaller than the females and of rather rare
occurrence, only appearing at certain times. They are recognized by
the peculiar modification of the first antennae. Testes and vas def-
erens are recognizable only at time of pairing. The reproductive
openings are upon the first abdominal somite. The spermatozoa
form masses known as spermatophores, a pair of which appear dur-
ing pairing, as little oval refractive bodies depending from the geni-
tal somite.

(b) Females. Look over several females until you find one in which the
ovaries appear as dark branching masses. These lie symmetrically
on either side of the alimentary canal, connected by one or two com-
missures. After fertilization, the eggs pass out from these through
openings in the first abdominal somite, and form a pair of external
egg-masses, the ovisacs, attached by stalks to the parent.

(c) Pairing. This may be observed only through chance, by continued
watching during the period in which males are abundant. The
male clasps the first antennae about the fifth pair of legs of the fe-
male, and directs a strong current of water towards her by a rapid
rowing motion of the legs. The two spermatophores, which appear
on the outside, become liberated by this and are carried across to the
female, to which they become attached. The ovisacs form soon
after this (15 min.-1 hour), taking but a few minutes for their forma-
tion.

(d) Larvae. The young free-swimming larvae of Cyclops are called Nau-
pliae, and are of theoretical importance from the occurrence of sim-
ilar larvae among widely different groups of Crustacea, thus furnish-
ing support for the theory that the Nauplias represents the primitive
Crustacean form. They are common in aquaria filled with females,
and are often seen in the field of the microscope during the study of

INVERTEBRATE ZOOLOGY. 105

the adults. A Nauplias is oval in form and possesses three pairs of
appendages used as legs. In later development these become the
first and second antennae and mandibles, while new somites and
appendages appear posterior to the original three, and develop into
the remainder of the body.

[76. Parasitic Copepoda. Many members of this group have forsaken their independent
existence and are found as parasites upon the gills or external surface of aquatic verte-
brates, representing all stages of degeneracy. Open the operculum or gill-flap of any fish,
marine or fresh water, and search among the reddish fringes (gills) for these forms. Some
are irregular, almost shapeless masses, tubular or sac-like, while others still show more or
less affinity to Cyclops. Even the most degenerate possess the lateral egg-sacs which, how-
ever, may appear as close coilsof tubules. When found, cut away the portion to which they
are attached, wash until clean and examine with lens. Ascertain mode of attachment, look-
ing especially for hooks, burrs, or other parts used in clinging to their host. Are these mod-
ifications of typical parts, or new formations ?]

Type XIV.—Simocephalus sp ? (or other typical Branchiopod).

77. General anatomy. The general structure may be ascertained from
living specimens placed under a cover-glass. They lie upon their side and are
flat and transparent, giving one the opportunity of using the higher lens. For
mode of motion, shape as seen from above, etc., they must be studied in a
watch-crystal.

(a) External anatomy. The shell is formed by an integumental duplica-
ture, that is, it is an exaggeration of a lateral fold. Focus on its
surface for peculiar markings upon it. The head is free and provided
with a short beak, the rostrum. The abdomen is slender and with-
out appendages. It moves rapidly back and forth, being capable of
projecting from beyond the margin of the shell. It is tipped with a
pair of curved terminal spines, above which is a row of smaller
spines. It is generally held in a curved position along the ventral
side. The eye is median (its true position being seen in a dorsal view)
and consists of a mass of black pigment, surrounded by highly re-
fractive bodies, the ‘* crystalline lenses.” The eye is moved by minute
muscular bands. There are two pairs of antennae, a short anterior
pair, near the rostrum, provided with knobbed olfactory hairs, and
an enormously developed second pair, the oar-antennae. These pos-
sess two branches, one of four and the other of three joints. They
are used for locomotion and thus functionally replace the legs which
bear gills and are used solely for respiration, These legs are seen

106

INVERTEBRATE ZOOLOGY.

through the shell, waving back and forth, thus beating the gills
through the water. There are five pairs of legs, of which the last
is placed at some little distance behind the others. The mouth parts
consist of a pair of mandibles and two pairs of maxillae, but are too
minute for general study.

Internal anatomy. The alimentary canal is somewhat curved, termi-
nating in the anal orifice. Where situated? Two small ‘ livers” or
hepatic diverticula lie in the head. Look at these from above. No-
tice the color of the food in different parts of the canal. Examine
a crushed specimen with high powers and ascertain of what the food
consists. In the neck region are a few very delicate wavy tubes,
running transverse to the longitudinal axis of the body. These form
the ‘‘shell gland,” an excretory organ, consisting of a mass of ne-
phridia, which open near the second maxillae. The nervous system
consists of a brain lying back of the eye, in the head, connected by
commissures to a chain of seven ventral ganglia. Dorsally, at the
beginning of the thorax, lies a little oval pulsating organ, the heart.
It possesses a pair of lateral ostia for the reception of the blood,
which is thence forced outward anteriorly. There are no blood-
vessels. The reproductive system is closely connected with organs
for the care of the young and the development, and should form
the subject of separate investigation.

78. Specimens may be kept in small aquaria, as in the case of Cyclops,

75.

Notice the following :—

Males. These appear only at certain times in the year, the females
reproducing at other times parthenogenetically. The testes are sim-
ple tubes ventral and parallel to the alimentary canal, tapering pos-
teriorly into vasa deferentia, which open ventrally in the abdominal
region. The males are best distinguished by the absence of the
brood cavity of the female.

Females. These are the common form, being often the only sex pres-
ent ina large aquarium. The ovaries lie in a similar position to the
testes. They are nearly transparent, but may be distinguished by
large cells, the eggs, which characterize them. The oviducts are at
the posterior end of these tubes, but open dorsally into a broad cav-
ity, and not ventrally, as in the case of the vasa deferentia. The
brood cavity is an oblong space, bounded above and at the sides by
the dorsal shell, ventrally by the alimentary canal, and is closed pos-

INVERTEBRATE ZOOLOGY. 107

teriorly by a pair of processes, which project dorsally from the ab-
domen, and which may be drawn downward to allow the escape of
the young. The brood cavity is filled witha special fluid for the
nourishment of the young, which develop here without metamor-
phosis and escape in the same form as the adult.

(c) Eggs and ephippium. The eggs which develop parthenogenetically
are thin shelled, develop very rapidly and produce only females.
Such eggs are called ‘‘summer” eggs. The fertilized or ‘* winter”
eggs are hard-shelled and receive, when in the brood cavity, a second
covering, called the saddle or ephippium, which is produced by the
shell. An ephippium contains in this species two eggs, and is depos-
ited in the mud, in which state the eggs can survive the winter, or
endure drying up. Winter eggs produce both sexes.

Type XV.—Cypris sp?

79, This is one of the most refractory objects of study, being too small
to dissect, too opaque to treat like the former two types, and covered with
thick chitinous shells, rendering it difficult to cut. It is best in a general
course to be content with a superficial examination. They may be first
studied alive, observing the movements of the shells, and of the appendages.
For special study of the latter, a large specimen may be selected and one lat-
eral shell lifted off with needles, or they may be opened by treatment with
hot Perenyi’s fluid [72]. The shell is closed by a transverse adductor muscle,
which unites the two valves at their centers. When this muscle is relaxed,
an elastic ligament, situated at the dorsal hinge, draws the shells apart. An
impression for the attachment of this muscle may be seen on the inner sur-
face of a clean, empty shell. There are only seven pairs of appendages,
borne on the anterior body portion, which corresponds to head and thorax ;
the abdomen is attenuated and resembles the appendages. The appendages,
with their forms and uses, are as follows :

Ant, |} Long, leg-like, used in locomotion. The second pair modified

Ant, in male.
Md Large—provided with a palpus, and flattened piece or fan-plate.

Mx, £Witha palpus and flattened fan-plate.

Mx, With asmall, two-jointed palpus, and rudimentary fan-plate.

Leg, This is often called the maxilliped. Used for locomotion.

Leg, ‘‘ Cleaning foot,” curved backward and used in cleaning out the
shell.

108 INVERTEBRATE ZOOLOGY.

80. Development. Cypris develops by a Nauplias, which is a fine illus-
tration of caenogenetic modification, or that modification by which an impor-
tant modern character develops during the repetition of an ancestral stage.
Here the Nauplias is provided with the characteristic bivalve shell. Search
at the bottom of an aquarium filled with Cypris, and examine the smallest
forms. The shells are transparent and some of them may be seen to possess
but three pairs of appendages, the number characteristic of Naupliae.

Bl. Comparison with barnacle larvae. The common barnacles, which
cover the rocks and all submerged objects at the sea-coasts, are modified
Crustacea, similar to Ostracods, which develop as free-swimming N aupliae,
and afterwards become sessile in an inverted position. When sessile, the
shells develop calcareous plates, and the appendages grow into delicate ten-
dril-like extremities, suitable to direct to the mouth a current of sea water,
containing nutritious material. The Nauplias larva is similar to that of the
Ostracods, and a later stage, the so-called ‘‘ Cypris” stage, is similar to the
adult. Barnacles may thus be considered modified Ostracods. The young
stages are commonly found in marine tow, which should be diluted and exam-
ined as in the case of Medusoids. The Naupliae of marine Copepods, simi-
lar to Cyclops, are also to be expected, but these are distinguished by the ab-
sence of lateral shells.

Type XVI.—A Spider (almost any form will do).

82. Luxternal characteristics. Spiders may be killed by chloroform, ben-
zine, or by immersion in alcohol. All spiders are venomous, but only the
large ones have mandibles powerful enough to penetrate the thick cuticle at
the finger tips. They can bite only what is beneath them, and may thus be
firmly grasped from above with the thumb and finger. They may often be
induced to drop into a wide mouthed bottle filled with alcohol, by holding it
beneath them, and poking them carefully with a stick. For external parts,
alcoholic specimens may be used, but large fresh specimens must be selected
for dissection. Investigate the following external characteristics :—

(a) Body. Two divisions, a cephalo-thorax and an abdomen. Anterior
end square with abrupt anterior edge, upon which are situated sim-
ple lenticular eyes, eight in most spiders. The arrangement and rel-
ative size of these is an important systematic distinction. Compare
and draw several different forms. The waist is attenuated and the
abdomen is generally so conyex dorsally that it laps over the poste-

INVERTEBRATE ZOOLOGY. 109

rior border of the thorax. Neither piece shows segmentation,
although the paired appendages indicate that it is a segmented ani-
mal. Is this consolidation a primitive characteristic, or is it a mod-
ification? Is the spider a high or low form ?

(b) Appendages. The cephalo-thorax possesses six pairs of appendages,
of which one is prae-oral.

1. Chelicers (mandibles). These depend downwards from the
abrupt anterior end. They consist of a powerful basal joint
and a movable tooth or poison fang. A poison gland in the
interior connects by a fine duct with this fang. In some
members of this class the chelicers bear a double claw.

2. Pedipalpi (palpi). These resemble legs in the female, but are
modified in the male into spoon-shaped organs, used to con-
vey the spermatozoa over to the female during pairing. In
some forms these also may become huge double claws (Ex.
Scorpion).

3-6. True legs. These are seven jointed and possess minute
toothed claws at their extremity. These are used in running
about on the web.

The abdomen of the embryo possesses rudimentary appendages,
some of which disappear, while others form the spinnerets or spin-
ning glands, at the end of the abdomen. How many pairs are
there? In cases where a median spinneret is present, how may it
be explained ?

(c) Respiratory and genital openings. Spiders breathe by a system of
plates, or fan-tracheae, which hang in respiratory chambers, the so-
called ** lungs.” A few tropical forms have two pairs of these, but
North American spiders have only a single pair. Look at the ven-
tral side of the abdomen, close to the cephalo-thorax, for a pair of
smooth, often shiny plates. These are the opercula, which cover the
respiratory chambers. This system is reinforced by a system of sim-
ple tracheal tubes, which open by a single median stigma just ante-
rior to the spinnerets. The female possesses a median opening as
outlet for the eggs, and two lateral openings for the reception of the
spermatozoa, and leading into spermothecae. The median opening,
or vagina, lies between or just posterior to the anterior pair of spin-
nerets, and the lateral openings at its sides. The vasa deferentia of
the male open by a median opening between the opercula,

110

INVERTEBRATE ZOOLOGY.

83. Anatomical Synopsis.

{A spider should be dissected in the same general way as other Arthropods ; the specimen
opened from the dorsal side by cutting around the eyes and removing the entire dorsal wall,
and then dissected under weak alcohol, pinned down ina small glass pan. As the specimens
should be large and fresh, it is impossible to provide material for a large class. Students
finding good specimens may make a general dissection, employing the following synopsis: |

il.

»

oO.

Alimentary canal. Muscular pharynx—long, narrow oesophagus,

running through a mass of nerve ganglia—thoracic enlargement
with paired diverticula reaching into legs and running around to the
ventral side—an abdominal portion, also showing a few diverticula,
(This, together with the thoracic enlargement, forms the chyle-
stomach. )—the short rectum and large rectal vesicle, a sort of cloaca
—a pair of Malpighian or urinary tubules which empty into the
rectum.

Nervous system. An almost solid mass, perforated by the oesophagus
and giving out paired nerves to the eyes, appendages, abdominal vis-
cera, etc. The portion dorsal to the oesophagus represents a supra-
oesophageal ganglion and the ventral portion, the consolidated ven-
tral chain. Some forms have a single small ventral ganglion just
posterior to the main mass.

Circulatory system. A dorsal vessel or ‘* heart” in the median line of

the abdomen, with three pairs of ostia to receive the blood from the
body, and anterior, posterior and lateral aortae, to send it to the dif-
ferent parts. These arteries are short and with open ends, the re-
mainder of the circulation being lacunar.

Respiratory system. Fan tracheae consisting of hanging plates with

double walls. The blood passes down between the walls of each plate
and is aerated by the supply of air in the respiratory chambers. Trach-
eal tubes somewhat similar to those of insects, a single median tube
arising from the single stigma, which branches into two main stems,
furnished with little tufts of tracheal tubes.

Reproductive system. Male: Two long tubular testes in abdomen,
becoming gradually more attenuated to form the vasa deferentia,
which are often much convoluted. They unite at the end and open
by amedian orifice. The pedipalpi serve as copulatory organs. The
inner side of the terminal joint contains a spiral tube opening at the
apex. This is filled with spermatozoa, which are thus conveyed to
the receptacula of the female. Female: The two ovaries are tubu-

INVERTEBRATE ZOOLOGY. 111

lar, but filled with large masses of egg-follicles, giving the whole
the appearance of a bunch of grapes. The short oviducts are con-
tinuous with these and unite with each other near the median open-
ing to form a short vagina. (Generally two receptacula seminis situ-
ated in close proximity to the median opening. In both sexes the
blind ends of the tubular germ glands may unite, forming a sort of
ring.

84. Development. Egg coccoons, formed by the mother, may be found
during the winter upon trees, and in summer among the webs. They are of
different species, but may be used indifferently. Examine for winter coccoons
any little rolled leaf or bit of leaf attached to the twigs, and look among
bushes for large round hanging masses. The detailed study of the develop-
ment requires careful technical manipulation, but a general idea may be
gained by studying the eggs with a lens or with the compound microscope.
During the early stages the eggs are opaque, but in later development the
growth of the embryo may be seen, the budding appendages, the appearance
of the eyes, etc.

Type XVE.—A Chilopod (preferably Lithobius).

85. Collecting and preserving. Myriapods are the ** thousand legged
worms,” found under the bark of decayed stumps, under logs, etc., in damp
woods, and occasionally in damp soil. The two orders are distinguished by
the legs, one having a single and one a double pair for each somite. Those
referred to here (Chilopoda) have a single pair for each somite and are some-
what depressed in form. Alcoholic specimens are sufficient for the work re-
quired here, which is merely the external anatomy. The internal anatomy is
very similar to that of insects, and the mode of investigation the same.

86. External anatomy. Note the well marked segmentation. Is there
distinction between body regions? Are the somites differentiated? Is this
higher or lower than a grasshopper? Study the parts in the following order :

1. The head. This may be removed from the body and studied in a
watch crystal. Be careful not to include the large curved pair of
jaws which are reflected upwards and lie over the mouth. They are
accessory mouth-parts, but belong to the thorax. The separate ap-
pendages may be temporarily mounted for special examination.
The eyes are small masses of simple eyes (ocelli) on the sides
of the head. One pair of antennae. Mouth parts consist of mandi-

112 INVERTEBRATE ZOOLOGY.

bles, and first and second maxillae. (Remove these in the reverse
order for convenience and study separately.) Compare each maxilla

' with the typical first maxilla of the grasshopper, consisting of basal
piece, inner and outer plate, and palpus. In what way does the sec-
ond maxilla differ from the type? The first maxilla?

2. The body (=thorax + abdomen). Study the appendages of the first
body somite, often called the maxilliped. Notice the inner plate
with its teeth, and the free leg. What is the probable use of this
free part? Notice a small opening on the inner side near the point.
This is the opening of a poison gland. Compare this maxilliped with
the second maxilla and with a free leg. To what does the palpus
correspond? Study a typical leg. How many joints? Can you
name them after the homology of the insect leg? [Type XVIII. ]
Look at the last four legs for coxal glands. Is the last pair of legs
any different? Why? Compare with the anal stylets of crickets
and cockroaches. The somite posterior to the one bearing the last
pair of legs is the genital somite, in which is the median genital
opening. The appendages are changed into accessory genital organs.
Are there differences in the two sexes? The final or anal somite is
without appendages and contains the anal orifice.

Type XVIIIl.—Caloptenus, sp?

[ Dissosteira (Oedipoda) the large form, with black and yellow wings, or any
other true grasshopper (Acrididae) may be used here. |

[As this is intended to be used as a preliminary study. the rules for dissection and other
technique will be given in full. Anatomical details, as relation, size and appearance of
parts, will also be given.]

87. Collecting, choice of material, preservation, etc. The majority of
grasshoppers are hatched in the early summer and grow continuously until
Sept.-Oct., when swarms of large adults may be found everywhere. Obtain
a few large forms, which may be caught in the fingers or with a small net,
and select from them those having the following characteristics : Body brown-
ish above, yellow beneath ; shanks of hind legs bright red ; a conical spine pro-
jecting from the throat, just beneath the chin. This last is the most important
characteristic and indicates the group of grasshoppers known as Caloptenus.
If this form cannot be obtained, some other large species may be used, but
one must expect to find some slight variation from the description given here.

INVERTEBRATE ZOOLOGY. 113

The sexes may be distinguished as follows: Male, smaller than female. with
darker colored body, terminating posteriorly in alarge rounded knob. Female,
often twice the size of the male, with large heavy body terminating in four
spines, which may approximate to form a single sharp spine for boring holes
in the ground to deposit the eggs. The sexes may be indifferently used as
specimens, except in the sections on the reproductive system. For immediate
use, or for the study of external parts, specimens may be dropped alive into
collecting bottles containing 70-80% alcohol. This will not penetrate the inte-
rior, however, sufficiently to preserve the inner organs. Benzine is the quick-
est and simplest killing agent and may be used whenever a specimen is to be
dissected at once. Dried specimens are often useful in the study of external
parts.

88. Symmetry, Form, Orientation: The body is biluteral, i. e. it may be
divided by one and only one plane, into two symmetrical halves. Locate this
plane. The halves are termed right and left. Imagine the animal resting on
a level surface in the natural position, and pass a plane through it, parallel to
the level surface and perpendicular to the first plane. Are these halves equal
and symmetrical? What are the characteristics of each, i. e. color, general
shape, thickness of shell, etc.? What external environments may have pro-
duced the difference ?

The upper half is termed dorsal, the lower, ventral. Pass a plane through
the middle of the body, perpendicular to the two preceding. This divides the
body into two halves, anterior and posterior. The above terms are also ap-
plied relatively, thus the inner pair of wings are ventral to the outer, although
both lie in the dorsal half. The exterior is hard, formed of plates which over-
lap each other, allowing the necessary motion, as in a suit of mediaeval
armor. This hard exterior is really the skeleton, and is termed exo-skeleton
in distinction from an internal, or endo-skeleton. The joints overlap each
other in the direction from which injuries are liable to come, or in the direc-
tion of the most usual motion. cf. the joints of the posterior half of the body.

89. Metamerism. Body regions. The body is divided transversely into
more or less separate joints or segments. The segments are also termed meta-
meres or somites, and an animal possessing them is said to be metameric or
segmented. cf. oyster and earth-worm. In a simple metameric animal, the
segments are all alike and distinct from each other, while in higher forms
segments may be suppressed, over developed, united together and modified in
many ways. This condition is considered higher because it has developed
from the first, and is for the purpose of doing certain things better ; thus the

114 INVERTEBRATE ZOOLOGY.

middle ventral region of the body may be consolidated into a single plate to
offer a better support for the legs. Is the grasshopper a higher or lower met-
americ animal? In higher forms the segments may be grouped into three
body regions or segment complexes, the lead, thorax and abdomen, each
equipped with its peculiar parts, and fitted to perform a certain range of
functions. The head bears the sense organs, antennae, eyes, etc., and pos-
sesses internally the central organ of the nervous system. the brain. Its
function is therefore psychic. The thorax bears the legs and wings, and con-
tains the largest of the body-muscles for moving these parts. It thus controls
the animal functions. The abdomen bears the organs for egg-laying, fertiliz-
ing the eggs, etc., and contains the reproductive and digestive organs. These
functions are shared by plants and are termed vegetative.

90. Morphology. Its methods. Morphology is the comparative study of
anatomical details. It considers every animal a plastic form, starting from a
simple primitive type, and moulded and modified to suit its peculiar environ-
ments and conditions of life. It thus seeks to express every anatomical detail
in terms of the typical form, rather than by means which are purely arbi-
trary. This may be made plain by referring to the following postulates, ap-
plicable to the group of animals under consideration.

1. Typical somite.* The grasshopper is too much modified to obtain from
it a clear idea of a simple unmodified somite; but the study of more primi-
tive forms yields the following conception :—An approximately circular ring,
composed mainly of two skeletal pieces, a larger, overlapping dorsal piece,
the tergite, and a smaller, ventral piece, the sternite. These are united by lat-
eral membranes, in which a farther pair of pieces may develop, the pleurites
or pleura. This somite bears a pair of joinled appendages, inserted between
the pleurite and sternite.

2. Typical animal (of this group). Corresponding to the above definition,
a typical animal would be formed by a series of such somites, each overlap-
ping the next posterior. Each somite must be of the same size and shape and
must contain the same organs. There are no actual animals corresponding
exactly to this description, but the more primitive members of this group ap-
proach nearer to it. cf. Chilopoda and Peripatus.

3. Modifications. The grasshopper may be considered as the result of a

series of gradually changing environments brought to bear upon the type

* The above description is that of skeletal parts merely.

INVERTEBRATE ZOOLOGY. 115

form, and must be compared with it, part by part. The most common modi-
fications of the type are the following :—

(a.) Eacessive development of a part. Ex. The tergite of the first seg-
ment of the body. In some species this extends beyond the end of
the abdomen.

(b.) Reduction of g part. Ex. The sternite of the same segment. The
reduction may lead to complete loss. -

(c.) Change of form to subserve a certain function. Ex. The antennae,
jaws and legs are all appendages.

(d.) Fusion of several parts. This is done wherever support is needed,
either for some powerful muscle, or against extensive injury. Ex.
The partial fusion of the sternites in the thorax, or the complete fu-
sion of the head to protect the brain. This change often affects the
somites themselves so that their identification is often difficult.

91. Rules for resolution of fused somites.

1. Aseach pair of appendages represents a somite, their number will
correspond to the minimum number of somites. Why the mini-
mum? This is called the ‘“‘ Rule of Savigny.”

2. Often internal parts retain metameric structure longer than external.
Why? Which parts are more directly under the influence of exter-
nal conditions? The nervous system is especially primitive in this
regard.

3. Individual development records past conditions more or less perfectly,

and thus parts fused in the adult may be separate in the embryo or
the larval form.

92. Special study of external details. Place a specimen upon the stage
of a dissecting microscope and examine with the lowest lens, controlling the
work with a pair of forceps in the left hand and a stout needle in the right.
For minute details use the higher lens. For some purposes the lens is best
removed from the microscope and used like a hand lens. If a specimen has
just been removed from a bottle of alcohol it should become dry before the
investigation to avoid the confusing refraction from the liquid.

1. Head. Remove this from the body, place it face towards you upon
the stage and notice :—The antennae, delicate organs of touch. How
many joints? The two large eyes at the sides. These are ‘* com-
pound,” composed of numerous facettes. Look at these with the

116

INVERTEBRATE ZOOLOGY.

higher power. The ocelli or simple eyes, one median, upon the ridge
between the antennae, and two lateral, at the inner, upper edge of
the compound eyes. The labrum, or upper lip, covering the mouth.
Lift this up and notice the two heavy black jaws, the mandibles.
These move laterally, and are toothed on the opposing inner sur-
faces. At the sides of the mandibles are four jointed tactile organs,
the palpi, attached to accessory mouth parts, not visible from
above. Look over the general surface for seams or sutures dividing
the head into separate areas. Of these the lateral pieces are the genae
or cheeks, the small median one just above the labrum is the clypeus,
and the remainder the epicranium. Make a large outline drawing of
the head from the front, putting in these details.

Mouth parts. Turn the head over and separate the loose pieces about
the mouth. The first (lowest) is a double piece with two palpi, then
will follow two lateral pieces, each resembling a half of the first
piece, and each with one palpus, and lastly the mandibles. These
pieces should be separately studied by placing them in a watch crys-
tal of 704% alcohol, and using the dissecting lens. The separate lat-
eral pieces are the mazillae, and the double piece the labiuwm or sec-
ond maxillae. Between them all is found a little fleshy projection,
the tongue. These parts, together with the labrum, constitute the
‘*mouth parts,” the arrangement of which is as follows :

labrum.
Ma. Md.
Tongue.
Me,. Max,.
Ma, + Mas.

All of these, with the exception of the tongue, are believed to repre-
sent appendages. The labrum is plainly a pair united in the middle,
and the notch in the center of the free margin of the labrum denotes
its double origin. Make a detailed drawing of the first maxilla and
the labium, noticing that each consists of a basal piece (two jointed)
two terminal plates, inner and outer, and a palpus. The palpi are
termed respectively, maxillary palpi and labial palpi.

Segmentation of the head. As the fusion is complete, this is done en-
tirely by counting the appendages, proving these, in doubtful cases,

INVERTEBRATE ZOOLOGY. oy

by their relationship to pairs of nerves which supply them. The
present solution is as follows :

Somite. Appendages.
I Antennae.
II Lateral ocelli.
Il Median ocellus (a fused pair).
IV Eyes.
V Labrum.
VI Mandibles.
VII First Maxillae.
VIII Second Maxillae (labium).

4. Thorax. This consists of three segments, termed respectively, pro-,
meso- and meta-thorax. Their tergites are termed pro-, meso- and
meta-notum, and their sternites, pro-, meso- and meta-sternum. The
terms ending in -ite, used in defining the parts of the type, are thus
only employed in the abdomen. The pro-thorax is free and mova-
ble. It consists of a broad pro-notum, forming a sort of collar, and
a very narrow pro-sternum, bearing a spine, the pro-thoracic tuber-
cle. Its appendages are the first pair of legs. The meso- and meta-
sternum are fused to give a firm support to the third or jumping
legs. They are reinforced by a portion of the first abdominal somite.
Dorsally they are divided up into a complex mass of small skeletal
elements, to give freedom of motion to the two pairs of wings which
are not appendages, but integumental folds which have become mov-
ably articulated with the rest of the skeleton. Ventrally a sternal
plate is formed, the sutures of which show its composition. The
most anterior piece is the meso-sternum, into which the meta-sternum
is fitted by a joint knownas a *‘ dove-tail.” The first abdominal ster-
nite is again dove-tailed into it, and forms the posterior portion of
the sternal plate. Make an outline drawing of the sternal plate.
The meso- and meta-thoracic legs are inserted at the posterior edges
of their respective segments. The plewra of the meso- and meta-
thorax are double, an episternwm in contact with the sternal plate,
and an epimeron above it. There are also a few minute pieces de-
veloped about the bases of the legs.

5. Legs. The first four are used for walking and the last pair for leap-
ing. They consist of the same parts, but their relative size differs
according to function. The two long joints are the ‘‘ thigh” (femur)

118 INVERTEBRATE ZOOLOGY.

and ‘‘shank” (tibia), the angle between them being termed the
‘“‘knee.” Between the body and the thigh are interposed two little
joints, cova and trochanter. Below the tibia extends the foot or
tarsus. This typically consists of five joints, the terminal one bear-
ing a pair of claws (wngues), but in the grasshopper the number is
reduced to three. Examine the pulvilli, or little pads, at the bottom
of the feet and see if you can explain this. Draw one of the legs.

6. Abdomen. The somites here conform nearly to the type, but lack
appendages and pleurites. They consist of tergite and sternite, and
are regular and plain except the first, which is fused ventrally with
the thorax, and at the end, where they are modified to accommodate
the reproductive organs and the outlet of the intestine. In this they
differ in the two sexes. In the female are four long hooks, the rhab-
dites or egg-guides. The ducts of the germ glands, and the alimen-
tary canal have their outlets among these terminal plates. Keep this
in mind and find the relationship of these parts, during the dissection
of these systems. In the dorsal portion of the first segment, under-
neath the wing, will be seen the ear, a vibratory membrane stretched
across a cavity.

93. Digestive system. For all internal dissections, use fresh specimens
and as large as possible. Hold the animal in the left hand with the head
toward you, and clip off with the scissors the legs, wings and antennae.
Then insert the point of the scissors just beneath the anterior edge of the pro-
notum, at the place where it bends over laterally, and cut through the exo-
skeleton, keeping on the side, as far as the end of the abdomen. Make a sim-
ilar incision on the other side. In this, keep the concealed point of the instru-
ment as near as possible the inner surface of the exo-skeleton, in order not to
wound the parts beneath. Then pin the animal to the wax of a small glass
dissecting pan, running the pins through the incision, close to the lateral
walls. Cover the specimen with 30% and place the pan upon a dissecting
microscope. Take the forceps in the left hand and the scalpel in the right,
and lift off the free dorsal piece, cutting off the connections as close as pos-
sible to the part to be removed. The internal organs will be seen lying in
place in the ventral portion of the exo-skeleton, which thus serves as a shell.
The alcohol renders transparent parts opaque, and the use of a liquid in dis-
section is for the purpose of unfolding delicate membranes, etc., which would
remain in air asa confused heap. (cf. the use of water in mounting “sea
mosses.”) If the pins be gently spread out, the walls will widen a little. The

INVERTEBRATE ZOOLOGY. 119

dissection consists of separating the different parts by cutting and teasing the
almost invisible connecting bands, and is best done by the forceps and the
sharp needle (the little spear-pointed instrument). The lens may be turned on
or off according to desire, and the microscope stage makes a good rest for the
little dissecting pan. Look first for the alimentary canal, a greenish or
brownish tube running through the median axis of the body. It is divided
into the following parts: Buccal or mouth cavity. This lies in the head and
is not seen in this dissection. It is merely the little cavity within and between
the mandibles. It is easily distinguished by its very dark brown walls.
Oesophagus, a narrow tube running straight upwards to the apex of the head.
There it makes a turn toward the neck. After passing the neck, the canal
suddenly swells out into a huge crop, tapering at both ends and filled gener-
ally with a dark brown fluid, which consists of the food mixed with some of
the digestive juices. This is the *‘molasses” which is disgorged to inspire
fear in its enemies. At the base of the crop the canal is re-inforced by
six finger-lhke expansions, which possess both anterior and posterior por-
tions. These are the gastric diverticula. They are hollow and thus reinforce
the general digestive surface. They empty into a portion of the canal which
forms the boundary between the crop and the stomach. It is called the pro-
ventriculus, and is developed in the cricket and others, into a little spherical
bag containing six hard, chitinous teeth. The stomach or ventriculus, is that
portion of the canal which extends from the diverticula to the place where
the canal is joined by countless little tubes appearing in a sort of tangle.
They are the urinary or Malpighian tubules, which absorb excretory material
from the body cavity in which they lie, and pour it into the lower portion of
the canal. How many separate bunches are there? The remainder of the
canal is termed the itestine, and may be divided into three portions, the
ileum, or tapering conical portion, the colon, of small size, and slightly coiled,
and the rectum, with six rectal glands.

The plate above the anus is termed the anal plate. Which is it? Draw the
canal and its parts, putting in the outlines of the body. Remove the en-
tire alimentary canal, cutting it through at its two ends, and place in a watch
crystal. Examine then the floor of the thorax for whitish masses something
in the form of bunches of grapes. These are the salivary glands, which form
anteriorly two tubes or ducts, opening into the mouth.

Return now to the alimentary canal; cut it open with the scissors, rinse
out the contents and examine the inner walls. The crop is marked by ridges,
which are surmounted by tiny teeth, pointing backward, to prevent regurgi-
tation of the solid food. (cf. later directions for mounting this.) Does the

120 INVERTEBRATE ZOOLOGY.

proventriculus give any indication of teeth as seen in the cricket? Can you
find the inner openings for the gastric diverticula? For the urinary tubules ?
What else do you find at the beginning of the intestine ?

94, Female reproductive system. Select for this a large female specimen
[87] and prepare as for digestive system. The large yellow masses lying dor-
sal to the intestine are the ovarial tubules, or organs for the formation of the
eggs. Part these in the middle and float them out at the sides of the body,
without cutting the tube with which they are connected. The mass will re-
solve itself under the lens into a collection of tapering tubules inserted by
their larger end into a large tube, the oviduct. How many separate ovarial
tubules compose one of the lateral masses? What is the condition of the
upper, free end of the oviduct? Trace the two oviducts down until you find
them uniting into one. What relation does this median tube sustain to the
alimentary canal? Trace it out to the external orifice and locate it. What
relation does it sustain to the rhabdites? The lower portion of the alimentary
canal may be removed if in the way. Look near the union of the two ovi-
ducts, and find alittle pyriform sac, connected by along duct with the exterior.
How is this connection made? The sac is the Receptaculuwm seminis, which
becomes filled during pairing with male germ-cells (spermatozoa), which may
then fertilize the separate eggs as they come down into the median tube.
Draw the entire system, putting inenough of the other parts to show relation-
ship. Cut off a separate tubule, remove the large egg at the end, and place
in the center of a clean slide. Put on a drop of the liquid used in dissection,
and lay on a cover-glass. If there are air bubbles, add more of the liquid,
drop by drop, until the cover-glass is full. If there is too much liquid, the
cover-glass will float and the excess of liquid must be withdrawn by applying
a cloth or bit of blotting paper. Such a preparation is termed a temporary
mount. Examine this with the compound microscope 60-80%. [As this instru-
ment is first introduced in this place, its use must be explained.| Of what
does the tubule consist? What idea do you gain concerning the formation of
eggs? Draw the specimen. [Stained preparations and sections will give
further information on this subject and will be studied later. |

95. Male reproductive system. This consists, like the female system, of a
system of tubules which secrete the germ cells, connected with excurrent
ducts. Prepare a male specimen as above, and examine the orange yellow
mass lying in the abdomen above the intestine. This is the fes/is, and may
be resolved into a double bundle of nearly transparent club-shaped sacs, sur-
rounded by a lace-work of yellow fat. The two bundles of spermatic tubules

INVERTEBRATE ZOOLOGY. 121

may be separated as in the case of the ovary, and found to connect with a
small tubule, the vas deferens.

The two vasa deferentia unite below into a common tube, as in the case of
the oviducts. A mass of coiled white tubules lying upon either side, con-
nect also with the common tube. How may this mass be resolved? The
tubules composing it may be termed prostate tubules and secrete a fluid me-
dium in which the minute germ-cells may be suspended. Make a drawing
illustrating this system. The finer anatomy of the tubules must be followed
by sections, as will be directed later.

96. Respiratory system. Inthe insect the air is brought into intimate
relation to all the organs of the body by a system of tracheal tubes which be-
gin at lateral openings (spiracles) and spread everywhere in the form of a
branching net-work. There is thus no venous blood, as it is constantly aérated
at every point. The disadvantage in this method is that such an animal must
remain of small size, for by this means it is impossible to furnish fresh air in
large quantities at a distance from the source of the supply. The arrange-
ment of spiracles and tracheal tubes in the grasshopper is as follows :

I. The Spiracles (stigmata).

These are the breathing-pores through which the respiratory system com-
municates with the exterior. There are ten pairs of these in two lateral rows
on thorax and abdomen. There are none on the head.

IDES Ha oP OKOS an ng oboe oociae ...On membrane between pro- and meso-
thorax, concealed by the posterior bor-
der of the pronotum.

DECONCMNOTACICG = eemer eee et oe On meso-thorax, just dorsal to the
opening for the articulation of the sec-
ond leg.

MinsteA bdominal=s. su soe Lee ae On first abdominal tergite at anterior
margin of auditory membrane.

Second—eighth Abdominal....... On the anterior ventral angle of abdom-
inal tergites 2-8.
Make an outline drawing of the body as seen from the side. Number the

somites and add the spiracles.

Il. Dissection of the respiratory system.

Use a fresh specimen, killed by benzine. (If alcohol be used for killing, do
not allow the specimen to remain in the liquid.) Open dorsally and pin into

122 INVERTEBRATE ZOOLOGY.

pan. Cover with water, as alcohol expels the air from the tubes and renders
them hard to see. Look for a system of fine tubes and sacks, which appear
silvery-white owing to the air confined within them. These are the tracheal
tubes, or tracheae, which extend from the spiracles to every part. They vary
greatly in size and shape, and may be thus placed under three categories :

1. Simple tubules. These are the most general, and in this form they
ramify every organ and form a capillary net-work of
extreme fineness. Different branches often anasto-
mose with each other.

2. Dilated tracheae. These are local enlargements of the above and are
found frequently along the main tubes. An impor-
tant branch often begins as a dilated trachea.

3. <Air-sacs or vesicles. These are sac-shaped expansions, connected with
the main system by small tubes. Their tracheal na-
ture is often emphasized by the appearance of
branching tubules which spring from the air-sacs
themselves.

The respiratory system is too complex to be followed throughout by dissec-
tion. The following series of dissections is given, from which the student
may select for special study according to the condition of the specimen used.
Make drawings.

1. System of abdominal air-sacs. There are five pairs of these connected
with abdominal spiracles 2-6. They differ considerably in the two sexes, as
follows :

Male. The last three pairs lie along the sides of the testis. Dorsally they
often give rise to branches which supply the superficial portion of
the testis. Ventrally they may be traced to the spiracles from which
they arise.

Female. Here the sacs are very superficial, flattened, and often pinkish
in color. They lie above the mass of ovarial tubules and connect
with the opposite sacs by a series of fine tubes forming a diamond
pattern.

2. Thoracic air-sacs. There are two pairs of these, of which the anterior
are enormous. They lie directly beneath the pronotum, and are often seen
projecting beyond its anterior edge in specimens from which the head has
been violently torn. The posterior pair lie in the meta-thorax and are much
smaller.

INVERTEBRATE ZOOLOGY. 123
°

3. The intestinal rosette. Thisis asset of dilated tracheae belonging to the
last three spiracles. It rests upon the dorsal side of the intestine and may be
seen by parting the ovaries and removing the overlying fat. It sends branches
to supply the rectum and the muscles of the rhabdites.

4. Dorsal intestinal vessels. These are two of the four main tubes which
run longitudinally through the body. They lie upon the alimentary canal and
extend from the intestinal rosette to the gastric diverticula. They are seen
by parting the ovarial or spermatic tubules and reflecting these masses
towards the sides. The intestinal vessels are often dilated in places and send
up branches to the ovaries or testes, which lie upon them. This supply in the
case of individuals with ripe ovaries, is exceedingly complicated and beau-
tiful.

5. Supply to the gastric diverticula. The arrangement here is very regu-
lar and is as follows: The six intervals between the six diverticula are so
arranged that two are dorsal (one median dorsal diverticulum lying between
them), two are lateral and two are ventral. The dorsal intestinal vessels send
out lateral branches, which, making six with the two ventral intestinal tu-
bules, occupy the six intervals ; the main dorsal intestinal vessels occupying
the two dorsal intervals, the two ventral intestinal vessels, the two ventral ;
and the two lateral branches from the dorsal intestinal vessels the two lateral.
Each of these six tubules divides anteriorly, the two branches supplying the
adjacent sides of the two anterior tubules bordering the intervals. Posteriorly
branches from the six tubules supply adjacent sides of the posterior diverti-
cula.

6. Supply to the crop. This is the most distinct because here the silvery-
white tubes ie upon a black back-ground. Four branches, two dorsal and
two ventral, extend from the neck-region posteriorly and meet four which ex-
tend anteriorly. The opposing branches anastomose and supply the walls of
the crop with a fine capillary net-work.

7. The spiracular tracheae. These are the tubules which come directly
from the spiracles. From each spiracle come two, dorsal and ventral, which
empty into their respective longitudinal intestinal vessel.

8. Thorax and head. The thorax is richly supplied with tracheal tubes,
but these lie interwoven among the muscle fibres and are difficult of demon-
stration. From the thoracic system two large tubes, the cephalic, pass ante-
riorly through the neck into the head. The terminal branches of these are
provided with very numerous small air-sacs. Of these, fifty-three were
counted in one specimen.

124 INVERTEBRATE ZOOLOGY.

. . . . dl
97. Nervous system. This consists of two portions which are more con-
veniently studied in separate dissections.

1. The ventral nerve cord. This lies in the centre of the ventral side, and
is found in the floor of the trough made by the body walls, after removal of
the alimentary canal and reproductive organs. Prepare a fresh specimen by
removal of these parts. or use one from which they have already been taken.
Wash carefully in 30% and place in 95%. Strong alcohol whitens and hardens
nervous matter. The nerve cord is easiest found in the abdomen, where it is
only slightly protected by internal prolongations of the skeleton. In the tho-
rax the cord is more carefully protected and is best dissected by tracing it up
from the abdomen and removing the overlying parts. The cord will be found
to consist of rounded bunches, the ganglia or nerve centers, connected by a
median nerve cord which is in reality double, as may be proven by removing
its sheath with a needle. From the ganglia fine nerves pass out to the sur-
rounding parts. How many abdominal ganglia are there? How many tho-
racic? Typically there is a ganglion to each segment, but in higher forms
there is more or less consolidation, especially at the end of the abdomen
where there is a modification of the original segments. Draw.

2. The ‘‘ brain” (supra-oesophageal ganglion) and the other structures of
the head. This is more delicate than any of the previous preparations, but is
done in the same manner. Remove the head from a large specimen, and,
holding it between the thumb and finger, shave off the surface of the face
with a sharp scalpel. Place it in the dissecting pan, cover with 95% and ex-
amine with the lens. Fine pins may be put through the extreme edge, to
hold it in place. A whitish mass will be imperfectly seen through the irregu-
lar hole made by the scalpel. This is the brain or swpra-oesophageal ganglion,
and may be brought into full view by cutting away the edges of the hole and
removing a mass of loose fat which often covers it. Notice the huge optic
lobes which go to the eyes, a pair of solid cups connected by stalks ; between
these a pair of ocellar lobes with nerves to the lateral ocelli; beneath, there
are a pair of antennal lobes, supplying nerves which run through the anten-
nae. In the center of the mass may be seen a short bit of nerve cut off from
its connection by the removal of the facial wall. This is the nerve to the me-
dian ocellus. Draw the brain. The brain lies dorsal to the alimentary canal
and connects with the remainder of the nervous system by a pair of large
nerves or commissures Which are found at the ventral lateral corners of the
brain, behind the antennal lobes. They may be followed around the oesoph-
agus, where they unite with the infra-oesophageal ganglion, the first of the

INVERTEBRATE ZOOLOGY. 125

ventral chain, supplying the mouth-parts. From this a nerve cord passes
through the neck and unites with the first thoracic ganglion.

98. Study of the minute structure of the parts (Histology). This is done
mainly by means of very thin sections artificially stained and cut by the
microtome. The sections are to be prepared by the instructor, mainly in ac-
cordance with rules given in this book, to be learned later by the students,
and distributed during the laboratory periods. The students are to bring to
the microtome a clean microscopic slide (object-glass), the center of which
has been smeared with a thin layer of Schillibaum’s collodion fixative. The
section, together with the paraffine, is placed upon this, heated gently by
passing it through the top of a Bunsen gas-flame two or three times (a hot
radiator is often sufficient) until the paraffine is melted. The slide is then
immersed in a jar of turpentine (a few drops of turpentine may be poured
over the slide instead) until the paraffine and excess of fixative are entirely
removed. The slide is then to be carefully wiped with a clean cloth, leaving
a small area about the section, a drop of Canada Balsam placed upon the sec-
tion and a cover-glass gently laid on. Imprisoned air-bubbles will work out
of the preparation in a short time. If correctly done, each portion of the sec-
tion should be in the same position as when in the paraffine. If a portion
floats off in the turpentine, the slide was not heated enough, or perhaps not
enough fixative was used. Too thick Balsam will often push the section
apart. Sections and other preparations may be made ad libitum of any por-
tion but the following preparations are recommended. They are best used to
accompany the dissection, but as fresh specimens are necessary for dissection,
while carefully preserved material is sufficient for sectioning, it is often expe-
dient to finish the dissection during the season in which living grasshoppers
are readily obtaimable.

1. Digestive system.

(a) Cross-section of crop in region of teeth.

(b) A piece of the wall mounted flat, to compare with the last. This
may be done by the student, as follows: Place in three watch-
crystals, 95%, 100%, and oil of cloves (or turpentine). Select the piece
desired and place it 5-10 minutes in each of the fluids and in the
order given. In this way the water is entirely extracted and the
specimen prepared for reception into the Balsam. For this, place a
drop of Balsam in the middle of a slide, and spread out the speci-
men in it, inner side uppermost. It is then to be covered in the
usual way.

126 INVERTEBRATE ZOOLOGY.

(c) Cross-section of gastric diverticula, anterior portion ; either sepa-
rately or in connection with the proventicular region of the alimen-
tary canal.

(d) Cross-section of stomach, anterior portion.

(e) Cross-section of stomach, posterior portion, including a snarl of uri-
nary tubules, which will be cut in all planes, longitudinal, cross, ete.

(f) Cross-section of intestine.

(g) Cross-section of rectum and rectal glands.

2. Female reproductive system.
(a) An ovarial tubule stained in Borax Carmine and mounted whole.
(Stained specimens may be given the student, which may be handled
as in 1 (b.)
(b) Cross-section of a mass of tubules, which will cut them at different
planes.

(c) Cross-sections of oviduct, in different places.
3. Male reproductive system.
(a) A spermatic tubule stained and mounted whole.

(b) A longitudinal section of a tubule showing the gradual transforma-
tion of the large cells at the apex (spermatoblasts) into the spermat-
ozoa. Such a section is very difficult and often impossible to furnish
to an entire class. A cross-section of a mass of tubules will give
many details which may be interpreted by reference to a single
longitudinal section.

(c) Cross-section of vas deferens.

4. Respiratory system.

(a) Temporary mount, unstained, of a mass of tracheal tubes, to show
the spiral thread.

(b) Permanent mount of a stained tubule to show the nuclei of the
intima.

5. Nervous system.

Sections through the brain are beautiful, and show well the arrange-
ment of the central cells, but the brains must be dissected out and
treated separately, and a single brain will not yield more than ten
good sections.

INVERTEBRATE ZOOLOGY. 127

6. Muscular fibres.
A few fibres may be isolated by picking them to pieces on a slide in
a drop of water. They may then be temporarily mounted to show
the striations. Stained muscular fibres will bring out the nuclei of
the investing membrane (Sarcolemma).

Type XIX.—Mya Edulis (or Venus Mercatoria).

99. Obtaining and preparing. Clams may be obtained inland at the fish-
markets and restaurants except during the coldest weather. The forms
named above are distinguished by fishermen as ‘‘ soft” and ‘‘ hard-shelled
clams” respectively. The first, Wya, is the one described here, but Venas
will be found to correspond very well. If the clams are laid in warm fresh
water for some time (the water is best left in the sun) they will become passive
or dead with the parts expanded. For histological details, as with other
forms of large size, the separate organs should be removed from a fresh spec-
imen and preserved with special reference to the object in view.

100. General dissection. Is the animal bilateral 2? Can you find the bi-
lateral plane? Are the shells dorsal and ventral, or right and left? Is the
animal compressed or depressed? Each shell has a knob at the top, the wmnbo,
from which proceed a series of concentric curves, the lines of growth, each
representing the edge of the shell at some former time. Were the shells
always of the same shape? The anterior end of the shells is more rounded,
the posterior more prolonged. Back of the umbo is an elastic ligament, the
hinge ligament, which tends to open the shells. Against this work two inter-
nal muscles, the adducturs, which stretch across from shell to shell. When
these are relaxed or cut, the shells open through the force exerted by the
hinge ligament. Each shell is lined by a delicate membrane, the palliuwm or
mantle, the edges of which project a little beyond the edges of the shell, and
are grown together, except at the anterior end, where a little space is left
through which projects a small muscular locomotive organ, the foot. Poste-
riorly the mantle forms a double tube, the siphon, which is capable of ex-
tending twice the length of the shell, or may be wholly retracted. Look for
two openings at the end. The ventral one, towards the free edges of the
shell, is the incurrent opening, branchial siphon, and the dorsal one, towards
the hinge, the excurrent, cloacal siphon. Place the animal upon its left side
(right side uppermost) and slip a scalpel along the edge close to the right
shell, separating it from mantle and siphon. Then reaching in further, and

128 INVERTEBRATE ZOOLOGY.

keeping close to the under surface of the shell, cut the two adductors, one
near the anterior, and one near the posterior end, lying towards the dorsal
side. Then remove the right shell entire, cutting through the hinge ligament.
Clean and dry the shell removed, and when dry notice :—The scars for the
anterior and posterior adductor muscles; near these, smaller scars for foot-
muscles, protractors and retractors ; a line parallel to the edge of the shell
where the mantle was attached, the pallial line, which curves in posteriorly
to form the pallial sinus for the reception of the siphon ; dorsally, the hinge,
where the two shells are articulated. Lift up the exposed mantle and notice
the relations of siphons, adductors, and foot. Find the opening for the foot.
The large ventral chamber now exposed is the infra-branchial chamber com-
municating with the exterior by the brachial siphon. Prove this. A large
rounded portion of the body with the foot attached, hangs free in this cavity,
upon each side of which are two delicate gill plates. In front of these are
four flat oral tentacles surrounding the mouth. Remove the remains of the
mantle and other overlying parts from just beneath the hinge and find the
heart, perforated by the intestine. Notice the pericardial chamber in which
it lies. Trace out the intestine posteriorly to the anal opening around the
posterior adductor muscle. With which siphonal opening does it communi-
cate? Cut through the membrane at the base of the gills, and thus expose
the supra-branchial or cloacal chamber. Notice the perforations in its floor
for the water which comes from the gills.

101. Dissection of special systems. The above section serves mainly to
give the general topography of the parts, and the location of the cavities.
As both shell and mantle are formed from an integumental fold, the infra-
branchial chamber is outside the true body and hence not comparable to a
coelom. The same may be said of the supra-branchial chamber. The pendu-
lous body mass is solid and consists of digestive tract, hepatic, and reproduc-
tive glands, packed firmly together and enclosed in a layer of muscle fibres.
The true coelom is thus limited to the pericardial chamber, which contains the
inner openings of the nephridia. After this general view, the anatomy of
each system should be studied, making use of different aspects and exposures,
using fresh specimens when necessary. For some systems, a complete ven-
tral or dorsal view is useful, obtained by removing both shells and pinning
the animal out as desired.

1. Respiratory system. Each gill-plate is composed of two layers, con-
nected by frequent commissures, bearing between them water-pores. The
blood circulates through blood spaces in the commissures and the lamellae

INVERTEBRATE ZOOLOGY. 129

themselves. The water enters the infra-branchial chamber through the
branchial siphon, passes through the water-pores into the supra-branchial
chamber and out through the cloacal siphon. The incurrent water brings
with it nutritive material which is taken up by the mouth, and the water in
the supra-branchial chamber receives waste material from nephridia and rec-
tum, as well as the generative products.

2. Circulatory system. Heart with median ventricle, perforated by intes-
tine, and two lateral auricles which lie at the base of the gills and receive
from them the aerated blood. From the ventricle proceed anterior and poste-
rior aortae, which branch into arteries that supply the body. From the open
termini of these, the blood passes into a lacunar system, through which it is
conveyed to the gills.

3. Ezacretory system. The paired organ of Bojanus lies below and some-
what posterior to the heart. Remove the gills at their base, and open the
supra-branchial chamber laterally. The organs appear as greyish-yellow
masses, and show a minute opening near their anterior end, the opening of the
ureter. The nephridial openings lie in the floor of the pericardial chamber
(=coelom), and may be demonstrated by opening the chamber dorsally and
removing the heart.

4. Digestive system. To dissect this, commence at the rectum and trace
the canal in an anterior direction to the mouth. It consists of a long, coiled
tube, running through the pendulous body, and closely packed in on all sides
by the liver above and the reproductive gland below. The muscular wall
of the body should be removed and the canal carefully separated from the
surrounding mass. A transparent rod is generally present, lying in the intes-
tine in the hepatic region. Its use is unknown.

5. Reproductive system. Bisexual, the male and female glands closely re-
sembling each other. The germ-glands are very numerous whitish masses, in
structure like bunches of grapes. The terminal duct collects the germ-cells
from all the bunches, and opens into the supra-branchial chamber, at the end
of a little papilla, which projects from the wall of the body just anterior to
the opening of the ureter.

6. Kebers Organ. A brownish mass lying upon the mantle just under the
hinge, and between the liver masses and the organ of Bojanus. Its use is
unknown, but it is probably connected with circulation or excretion.

~

i. Nervous system consists of three main double ganglia connected with
commissures, and of nerves which proceed from the ganglia and supply the

130 INVERTEBRATE ZOOLOGY.

different parts. The cerebral ganglia lie above the mouth, upon the anterior
adductor muscle. The visceral ganglia lie upon the posterior adductor, under-
neath. The pedal ganglia lie in the anterior part of the foot. The commis-
sures are the cerebro-visceral, lying superficially above the base of the gills ;
and the cerebro-pedal, through the visceral mass.

Type XX.—Helix Pomatia.

(This is the large vineyard snail of Europe. Any large native Helix may be
used instead. )

102. Obtaining and preserving. Helix Pomatia is used in Europe as a
common article of diet. It hibernates under leaves and stones, first closing
the mouth of its shell with a layer of lime (epiphragma). In this state it is
gathered in quantity and sent to the cities, and may be occasionally obtained
in the large restaurants of American cities (Philadelphia). When obtained,
break out the epiphragma and the snail will resume its activity. The com-
mon New England form, H. albolabris, is very typical in structure, but much
smaller and seldom found in quantity sufficient for class use. It occurs in
damp woods, crawling over moss or resting beneath stones or pieces of de-
eayed wood. The ordinary methods of killing cannot be applied to snails, as
they will withdraw into their shells at the least alarm. To obviate this, use
the following method :—Place the snails in a jar which can be hermetically
closed, and fill it entirely with water, by immersing the whole in a pail, and
closing the jar while immersed. In this the snails will become slowly asphyx-
jiated (24-36 hours) and will remain expanded, after which they can be fixed
and preserved in the usual way. Water from which the air has been expelled
by boiling will accomplish the end more speedily. The result may be also
hastened by the addition of a little chloral hydrate (2-8 7).

103. External characteristics. An expanded animal may be seen to con-
sist of three portions ; head, foot and visceral sac. The latter is contained in
a spiral shell, which may also contain the other two when contracted. In
what respects does the shell differ from that of a clam? Is it bilateral? If
it were plastic and capable of being unrolled, could it be placed so as to be-
come so? What would then be the shape of the visceral sac? Are the head
and foot bilateral? Is it probable that the shell and visceral sac were origi-
nally bilateral also? Is the shell carried exactly on the top of the animal, or
inclined to one side? Is this always the same side? Which? Viewing the
shell from above, it is seen to consist of a gradually expanding spiral, wound

INVERTEBRATE ZOOLOGY. 131

about a center, the apex. Is the spiral wound towards the right (with the
hands of a watch) or in the opposite direction? Are all specimens alike in
this? The separate spirals are divided from each other by a crease, the suture.
The open end of the last spiral is termed the ‘‘ Mouth,” and its free edge. the
“lip.” Notice the slightly curved lines upon the spirals, at right angles to
the suture. What is their significance? Do they correspond to anything on
the surface of a clam shell? On the head notice :—The long tentacles (omma-
tophores) which bear at their tips the eyes and probably the olfactory organs ;
the short tentacles ; the genital opening on the right side, at the base of the
ommatophore (behind the short tentacle in H. albolabris): the mouth, sur-
rounded by soft lobes, the lips. Probe the mouth gently with a needle and
feel a hard chitinous dorsal piece, the jaw or maxilla. Beneath the margin of
the shell on the right side, notice an opening, the breathing pore or pneumo-
stome, which opens into a large respiratory sac, the so-called ‘‘Iung.” The
intestine runs along the wall of this sac and opens at the edge of the pneumo-
stome. The nephridial opening is at the same place, but cannot be demon-
strated from the exterior. During life the pneumostome is under the control
of muscles. The foot is provided with a flat creeping sole, posteriorly pro-
longed, and running anteriorly beneath the head, nearly as far as the mouth.

104, Dissection. Carefully remove the shell, beginning at the edge and
taking it away in little pieces. Notice that the shell has a central support,
the columella, about which the visceral sac is wound. Commencing below,
uncoil the visceral sac, removing every vestige of columella and shell. The
entire visceral sac is covered by a delicate membrane, the mantle, which en-
closes the organs, and has a thickened edge below, the mantle ridge, which
marks the boundary of the shell. Pass a probe into the pneumostome. It en-
ters the respiratory chamber, and may be seen through its transparent wall.
Open this chamber with the scissors, and notice upon the right side ;—the
heart, enclosed in a delicate sac, the pericardium ; the nephridial organ with
its duct, and the rectum, terminating in the anus. A rich net-work of blood-
vessels is spread over the walls. The floor of the lung-chamber is formed by
the body-wall, which covers the visceral organs and thus shuts off the res-
piratory chamber from the coelom. (cf. the branchial chambers of the cray
fish and the clam.) For farther dissection make a median dorsal incision,
beginning just above the mouth. Carry it posteriorly through the mantle-
ridge and the floor of the respiratory chamber. As it is difficult to continue
a mid-dorsal incision upon the coiled visceral sac, the entire mantle may be
removed from this, thus liberating the organs. All the cavities of the body

132 INVERTEBRATE ZOOLOGY.

are thus opened and the organs exposed for study. The specimen should be
pinned down ina dissecting pan, the cut edges of the body wall drawn apart,
and the separate systems studied. The parts are to be identified by the synop-
sis given below, the details of form and relationship are to be left to the stu-
dent. It is well to notice the following points: The alimentary canal may
be isolated first, following the windings of the intestine to the apex of the
spirals and back to the respiratory chamber. The large brown organ filling
the spirals is the liver, and should be removed with the canal. Take great
care and not harm the hermaphroditic gland, or its duct, lying in close con-
nection with the liver and intestine near the apex. Observe the central
ganglia of the nervous system lying upon the pharynx, and do not investi-
gate the interior of the pharynx until the nervous system has been studied.
When this is done, remove the pharynx for detailed study. Find the mailla
and the radula, a tough membrane covered with countless minute teeth, in
the interior of the pharyngeal cavity. This should be removed and mounted
in Balsam.

105. Anatomical Synopsis.

1. Digestive system. Pharynx, an oval organ with very muscular walls,
in which lie the maxilla and the radula—Short oesophagus expand-
ing into the large fusiform stomuch—Salivary glands, lying on each
side of the stomach, with long ducts, which open into the pharynx—
Intestine, which shows an enlarged area where the ducts of the liver
enter—Liver, several large dark-brown lobes, closely packed in the
upper part of the spiral—Anus, in the wall of the respiratory cham-
ber, close to the pneumostome.

2. Reproductive system. Hermaphroditic gland and duct at apex of sac
albuminous gland, a large white mass with a free end—wterus or
oviduct, a somewhat coiled crenate tube, accompanied on one side
by a smaller tube, the vas deferens—This latter leaves the oviduct,
makes a turn upon itself and expands into a sheath which contains
the penis or organ of copulation. The sheath opens at the genital
orifice—The fiagellum, a gland in the form of a long free tube at the
inner end of the penis-sheath—At end of oviduct a sac and two
bunches of finger-like glands. The sac contains a spicule which aids
in copulation, the so-called ‘*‘ Cupid’s arrow ” (Liebespfeil) ; the glands
probably assist in the formation of the egg-shell—The spermatheca,
a spherical sac, communicating by a long slender duct with the
lower portion of the oviduct.

INVERTEBRATE ZOOLOGY. 138

3. Circulatory and respiratory systems. Heart, with one atriwm and one
ventricle, distinguished by the thickness of their walls. The circu-
lation is partly in blood vessels, and partly lacunar, there being no
capillaries. The blood from the coelom and other blood sinuses is
brought into the respiratory chamber by a ring-vessel, which runs
along the mantle-ridge and branches into a net-work of fine vessels.
These are re-collected into a pulmonary vein, which conveys the now
aerated blood to the atrium. A single aorta passes from the ventricle,
but soon gives off the visceral artery towards the apex of the visceral
sac. The aorta then passes into the body cavity. Its main branches
are intestinal, genital, salivary and pedal, to the corresponding parts.

4. Nervous system. The three typical ganglia, as seen in the clam, are
here united into a complex lying upon the pharynx. The cerebral
ganglion is anterior, connected by a double commissure to the viscero-
pedal ganglion just posterior to it. This latter is perforated by an
artery which divides it into an upper (—pedal) and a lower (—visce-
ral), Anterior to the cerebral is a small pair, attached by commis-
sures, the stomato-pedal. The following are the main nerves :—
From cerebral ganglion : tentacular (to ommatophores) ouwter-labial,
inner-labial, facial (to front of head and short tentacles) auditory (to
ear-sacs on side of pedal ganglion) a median nerve to the penis.
From viscero-pedal: genital (to reproductive organs and heart), an-
terior, middle and posterior mantle nerves. A large number to foot,
mostly small.

Type XXI.—Bugula sp?

106. Occurrence. Preservation. Bugulais a colonial polyp closely re-
sembling a hydroid, and found on all sorts of submerged and floating objects,
especially on eel-grass. Under the lens a branch resolves itself into a colony
of sessile animals living in cells, into which they are capable of entirely with-
drawing. As the skeletal portion is very durable, a great many of the
branches collected will be found partially or wholly empty, and thus each
specimen must be examined before preserving. They should be treated as in
the case of hydroids in order to prevent the retraction of parts.

107. Study of a stained specimen. Select a good branch fixed with parts
expanded, and stain and mount entire. Notice the separate cups or cells,

zooecia, in which the separate animals live. How are they ar ranged, rela-
10

134 INVERTEBRATE ZOOLOGY.

tively ? Look along the edges at the bases of the zooecia, for little pairs of
jaws, something like birds’ beaks, mounted on pedicles. These are the avic-
ularia, probably specialized individuals, fitted to detain and hold animals
which will attract the small forms upon which Bugula feeds. At the bases
of the separate zooecia are sometimes found oval cysts containing a single
egg. These are ooecia, which may be another specialized form, or have the
worth merely of a brood capsule. The animal itself bears a series of tenta-
cles, upon a semi-circular ridge, the lophophore. How many tentacles are
there? They differ from those of hydroids in the presence of cilia and in the
absence of cnidoblasts. The alimentary canal consists of pharynx, stomach
with a terminal coecum, intestine and rectum. As in most sessile forms the
canal curves back upon itself, the anus lying just outside the lophophore. A
muscular cord, the funiculus, extends from the coecum to the bottom of the
cup, probably to prevent over-extension of the parts. Ovaries develop on the
body-wall near the coecum. ‘Testes appear upon the funiculus. The polyps
are hermaphroditic.

108. Eor special examination of the skeleton, soak a colony in K-O-H,
wash in water and examine. This will bring out the details of the avicu-
laria, etc.

Type XXIl.—Asterias vulgaris.

109. Collecting and preserving. This is the common star fish, abundant
everywhere at the sea-coast and obtained at low tide, especially about mussel-
beds and the piles of wharves. They are preserved for ordinary dissection by
being put alive into 957, as they are porous enough to allow free entrance of
the fluid, and contain sufficient water to dilute the alcohol. For histology the
separate parts should be dissected out and preserved.

110. external characteristics. Is the star-fish bilaterally symmetrical ?
How many planes will divide the animal symmetrically? Such a structure is
termed radiate. Upon what number is the radial symmetry based? What is
the usual number among Cnidaria? The body is divided into a central por-
tion or disc, and five triangular projections, the rays. The distinction be-
tween the two is slight here, but very definite in the ‘‘ serpent-stars ” (Ophiu-
ridea). Compare the two surfaces ; the flatter of the two is beneath when the
animal crawls, and has the mouth in its centre, and thus is called the oral
surface. The other is the ab-oral surface. Oral side :—Notice the central
mouth, its shape—very numerous soft tentacles, the ambulacral feet, extend-

INVERTEBRATE ZOOLOGY. 135

ing through the center of each ray as far as the tip. How many rows are
there? Cut them entirely away from a small area and notice the pores in the
floor of the ambulacral groove, through which they are projected. These are
the ambulacral pores. Have they a definite arrangement? In another area,
part the rows of feet in the middle and expose a central ridge, the nervous
cord, which proceeds from a central ring. Follow this out to the point of a
ray and note the pigment eye. Ab-oral side :—Notice the plates beset with
spines. Are there soft spaces between these plates? Notice often in these,
projections called papulae, very thin portions of the integument which pro-
ject out between the spines, and in the living animal are very sensitive and
capable of sudden withdrawal. These, as well as the ambulacral feet, are
used in respiration, as a special respiratory system fails. Search with a lens
among the spines for minute organs, appearing like little knobs mounted on
exceedingly delicate stalks. These are the pedicellariae, and appear under
the microscope as tiny forceps, some two- and some three-tined. They are
used to pick grains of sand and all forms of debris from among the spines.
Treatment with K-O-H will resolve the skeletal structure of these. Upon
the disc, at one side notice a raised circular plate, the only departure from
the radial symmetry. It is the madrepore plate, a porous structure through
which the water passes in to the ambulacral system (see below).

{44. Dissection. The entire ab-oral surface should be removed, cutting
through the edges of the rays with the scissors, and entirely around the
madrepore plate, leaving it with the preparation. The disc is filled with the
stomach, a delicate membrane, much folded and wrinkled. Five lobes may
be found, which pass out a short way into the rays; above, a very small and
tapering intestine leads to a minute anus, cut off by the removal of the disc.
In each ray are a pair of brownish tree-like structures, the hepatic organs,
each of which possesses a central duct. The two ducts in each ray unite into
a median duct, which opens into the gastric diverticulum of that ray. At
the base of each ray are two sexual glands (very small in immature specimens)
the ducts from which unite in such a manner that the glands of two adjacent
rays open by a common orifice in the interradial angle. The most character-
istic system is the water vascular or ambulacral. The madrepore plate is con-
tinuous with a sinuous canal, the stone canal, which may be followed into a
circular ridge. This ridge conceals the ambulacral ring, from which five
radial ambulacral vessels proceed through the center of each ray The course
of this canal is also through skeletal pieces, and is marked by a median ridge
in the floor of each ray. From this canal, very numerous lateral branches

136 INVERTEBRATE ZOOLOGY.

supply little oval vesicles, the ampullae, of which the ambulacral feet are the
continuation. The entire apparatus forms a system by means of which water
may be forced into and out of the ambulacral feet, causing them to be pushed
out and withdrawn. The relation of these parts is best understood through
the aid of cross-sections of a ray [113].

112. Study of skeletal plates. Cut off a ray and boil it in a test tube of
K-O-H until it falls apart. The little plates composing the skeleton are sep-
arated by this means. Wash several times by decantation and finally bring
the whole into a Stender dish for study. Compare these with another speci-
men, not boiled as much, and in which the plates still hold together. The
procedure can be regulated as desired by different degrees of dilution of the
reagent, and by varying the time of boiling. Obtain by these means an accu-
rate idea of the architecture of the skeletal plates, and express the result by
a diagram.

113. Cross-section of a ray. Select for this a few very small star-fish
and preserve by warm alcoholic sublimate. When sections are desired, re-
move a ray and decalcify by letting it stand several days (as long as necessary)
in a dish of picric acid, to which has been added a trace of nitric acid. The
acid should be daily changed and the process continued until the specimen is
no longer gritty when tested with a needle. Wash out in 707, and stain
(2-8 days) in Alum Carmine. Dehydrate, imbed and section as usual.

114. Larval forms. These are captured by the tow net. They are the
famous bipennariae and brachiolariae. They may be investigated as in the
case of other forms found in tow (nauplias, etc.) and may be mounted either
stained or unstained. Handle with a pipette, or upon a slide.

TYPE XXIll.—Arbacia punctulata.
Strongylocentrotus Drobachiensis.

115. Occurrence and preservation. These are the ‘‘ sea-urchins ” common
on every coast. Arbacia is the small dark-purple form, found from Massa-
chusetts Bay southward, and Strongylocentrotus is the larger olive-green
species, with smaller spines, common farther north. Either species will do, the
minor differences making the comparison interesting. They may be preserved
as in the case of Asterias, but an artificial opening should be made into the
interior to allow the passage of the alcohol, as the skeleton is much firmer
than in the star-fish. A slit through the peristome, along the edge of the test,
is the most practical.

INVERTEBRATE ZOOLOGY. 137

{16. eternal anatomy. Study and explain the symmetry of the ani-
mal. Whatis the shape of the shell? Find the oral and ab-oral aspects.
Oral side :—In the center, the circular lip, surrounding five teeth, set in hard
jaws. The soft area continuous with the lip is the peristome, reaching to the
margin of the shell or test. Upon the peristome are ten large ambulacral ten-
tacles, surrounded by pedicellariae. At the border of the test are the oral
ends of five rows of ambulacral feet. Trace these around upon the ab-oral
side. Ab-oral side :—In the center, the anus protected by four anal plates (in
Strongylocentrotus the four plates are replaced by numerous little oval
plates). Surrounding the anal plates are five large genital plates, alternating
with five small ocellar plates. One of the genital plates includes the madre-
poric area. Find the genital openings and the eye spots in their respective
plates. What relation do these plates sustain to the rows of ambulacral feet ?

Spines and test :—Notice the spines. Tear one away from the test and no-
tice the articulation. Have the spines any regular arrangement? Can the
position and size of the spines be determined on a denuded test? Beginning
at the anus, pull off the spine from a considerable area, including a row of
ambulacral feet and the entire space between two rows. Notice that the po-
sition of the ambulacral feet is indicated by two rows of perforated plates,
while the space between two ambulacral rows is filled by two rows of larger
plates. The area of the feet is termed the ambulacral area, and the space be-
tween them the inter-ambulacral area. Which bears the largest spines? What
is the arrangement of the ambulacral feet (as determined by the ambulacral
pores)? What is the total number of rows of plates running meridionally
around the test? [After the dissection, the test may be cleaned by boiling in
dilute K-O-H, and the separate plates isolated. If a perfect test be taken, the
separate skeletal elements may be mounted on a black card as in the diagram
of LANG].

{47. Dissection. This should be performed from the oral side. Remove
the peristome and crack away the margin of the test as far as desired. In
the centre lie the teeth and jaws, forming a symmetrical cone-shaped mass,
** Aristotle’s lantern.” Lift this carefully and notice that the alimentary
canal runs through it, the free part beginning at the center of its base. Sepa-
rate and study the parts of the ‘‘lantern.” It is moved by muscles attached
to the edge of the test, and from one part to another of the lantern itself.
The internal anatomy is similar to that of Asterias, presenting, however,
interesting minor differences in every system. Dissect it carefully and com-
pare step by step.

138 INVERTEBRATE ZOOLOGY.

£48. Study of larvae. These are found in tow and are to be treated as
in 114. The larva is termed the Plutews, similar to that of Ophiuridea, but
distinguished from that of other Echinoderms by the great length of the lat-
eral arms.

Type XXIV.—Balanoglossus sp?

{49. Occurrence. This is one of the numerous forms of mud-worms or
clam-worms, found in mud-flats at low tide. It formerly received but little
attention. but has lately become an important form, on account of its proba-
ble kinship to Tunicata, and hence its relationship to Vertebrates. According
to some it possesses also affinity to the Echinoderms. Some species develop
directly, others by a free-swimming pelagic larva, the Tornaria, similar to
the larvae of Echinoderms.

120. External anatomy. The body is bilateral and divided into three
regions, proboscis, collar and body proper. The first two are rounded, the
body somewhat depressed. The dorsal side is marked by the presence of
puired gill-slits, which lead from the alimentary canal, and open dorsally by a
series of pores. A median stripe upon both dorsal and ventral surfaces marks
the position of median blood-vessels and median nerve cords. The mouth leads
in from the anterior edge of the collar upon the ventral side. The anus is
situated at the posterior extremity.

{2t. Internal anatomy. Owing to the small size of the animal, and the
partial filling up of the coelom with muscular fibres and connective tissue,
simple dissection is impracticable. The parts and their relations must be
studied by sections, the preparation of whichis rendered difficult by the pecu-
liar consistency of the animal. Treated in the usual way, the tissues are apt
to harden to the consistence of horn, and become impossible to cut. Better
results may be obtained by imbedding in celloidin. The most useful sections
are cross-sections through the lower portion of the proboscis, the collar and
the branchial region of the body; and a median longitudinal section cut
dorso-ventrally through the anterior portion. The following synopsis of the
systems may be helpful :

1. Digestive system. A nearly straight canal, running through the entire
body, from the ventrally situated mouth at anterior edge of collar, to the ter-
minal anus. Of morphological importance is an anteriorly extended dorsal
diverticulum in the region of the collar, considered by some the homologue of

INVERTEBRATE ZOOLOGY. 139

the notochord of the Chordata. A skeletal body, probably secreted by this
last, lies between it and the dorsal-wall of the alimentary canal. and sends
two processes around the canal itself. This is important as showing a skele-
togenous quality in the diverticulum.

2. Circulatory system. Two median vessels, dorsal and ventral, which
give off lateral twigs. At the anterior end of the dorsal vessel, lying upon
the diverticulum, the vessel is enlarged, forming what KOHLER and BaTESoN
call the ‘‘ heart.”

3. Respiratory system. The ‘‘gills” consist of paired diverticula of the
dorsal-wall of the intestine opening externally through pores in the dorsal
integument. The blood passes to these either through the lateral branches
above given, or from a pair of lateral vessels (KOWALEVSKY).

4. Reproductive system. Bisexual: the two sorts of glands closely resem-
bling each other. They consist of paired glandular pockets opening separately
by pores on the dorsal side. Some of these lie in the gill-region, but are gen-
erally best developed in the region just posterior to this.

5. Eacretory system. This function has been ascribed by BaTEson to the
dorsal pore, a minute tube passing into the proboscis from a median dorsal
opening just beneath the edge of the collar. According to others (SPENGEL),
the dorsal pore is a means by which water passes into the proboscis, making
the latter an ambulacral organ.

6. Nervous system. The central organ is a thick cord lying dorsally in the
collar region, from which extends a mid-dorsal cord through the body, accom-
panying the dorsal blood-vessel. Immediately behind the collar the dorsal
cord gives off two:lateral commissures, which unite ventrally in the region of
the first pair of gill-diverticula, and form a mid-ventral cord, which follows
the blood-vessel of the same name.

122. Study of Tornaria larva. Certain species of Balanoglossus possess
a free-swimming larva, the Tornaria, occurring in oceanic tow collected near
the regions inhabited by the adult. They are studied and prepared in the
same manner as other minute larvae.

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