abdomen and a postabdomcn
(see Fig, 198).
In the internal structure quite as striking similarities are to be found
in the presence of an endosternite in both groups and of coxal glands in
connection with the fifth pair of appendages, in the tendt .cv towards the
eencentration of the postoral ganglia, and in the invaginate'origin of the
median eyes, to mention but a few points.
The Arachnida are accordingly to be traced back to Limulus or Euryp.
temsAxkQ ancestors, and through thes.,' finally to the Entomostraca, perliaps
a C rustacean ancestry being clearly indicated. As to the relationslni)s of
tiio .anous orders little that is definite can l)e said, differentiations liaving
taken place along different lines in the various orders, so that while the
LEY).
1 = indifferent .stage.
// = Limulus stage.
A = Aia(;lini(ian staffc.
3
458
INVEliTEDliA TE MOIWIIOLOO Y.
Pedipalpi arc more pi'itnitive as regards the number of abdominal seg-
ments and their distinctness than tiie Aranea", yet the hitter and especially
the Tetrapneunioiies show a much more primitive condition of tlie respira-
tory oi'gans. With regard to tliese organs it may be at; d that the con-
dition in which they are represented by buuciies of un iunched tracheae
is more primitive than that in which they are branching tubes, the
bunched condition being probably derived by a modification of original
lung- books.
TYPE ARACHNIDA.
1. Order /Scorp/omrfa. — Abdomen segmented and differentiated into pra;-
abdoraenand postabdomen ; postabdomen terminating in poison-
spine ; pedipalps chelate ; two pairs of abdominal api)endages ;
four of stigmata and lung-books. Euscorpius, Bathus.
3. Order Pseiidoscorpioithla. — Abdomen segmented but not differentiated ;
no terminal spine ; pedipalps chelate ; no abdominal appen-
dages; two pairs of stigmata opening into trachea;: first pair
of legs adapted for locomotion. CheUfei\ Obisiuvi, Cheriiea.
8. vU'dei Solifugw. — Head separated from tliorax with thret; segments;
abdomen segmented but undifferentiated ; no terminal spiiu; ;
pedipalps palplike ; three pairs of stigmata leading into trachea\
Oaleodes, Solpuga.
4. Order Pedipalpi. — No distinction of head and thorax ; abdomen seg-
mented, and either undifferentiated or with three small segments
terminated by a multiarticulate tlagellum ; pedipalps leglike or
subchelate ; two pairs of stigmata and lung-books ; first pair of
legs elongated and palplike. Phryntts, ThehjpUonus.
5. Order Pltalamjlda. — Abdomen segmented but undifferentiated and
without appendages or terminal spine ; pedipalps leglike ; one
pair of stigmata leading into trachea; ; no spinning-glands.
Leiohunum, P/ialanyium, Opilio, Qonyleptus, Cyphophthalmus,
GibbocelluiH.
6. Order Araiieir. — Abdomen nnsegmonted and with two or three pairs of
rudimentary papillalike appendages bearing the openings of
ducts of numerous spinning-glands ; abdomen not fused with
eephalothorax ; pedipalps long and palplike or leglike.
1. Suborder Tetrapneumonen. — With four stigmata opening into
sacs containing lung-books. Mygale, Cteniza.
2. Suborder Dipnenmones. — With four or three stigmata, the anterior
pair opening into sacs with lung-books, the posterior one or
two with trachea?. Epeira, Agelena, Tegenaria, Tlierkliniit,
Segestria, Attus, Lycosa.
7. Order Acarina. — Abdomen unsegmented, without appendages, ami
fused with the eephalothorax ; pedipalps sometimes long uml
leglike, sometimes chelate ; stigmata wanting or present as a
TYPE AUACUNIDA.
ilorainal seg-
nd especially
[ the respira-
thiit the con-
;he(l tracheie
; tubes, the
I of original
469
single pair leading into tracheue ; many forms parasitic • fre-
quently with complicated metamorplioses. '
Nonparasitic, or ])arasitic only in larval stage ; terrestrial Ori-
Oates, JVothntfi, TrombkUum.
A(iuatic. HydracluM, A tax.
Living on organic matter. Ti/rof/li/p/nis.
Parasitic on animals. Deinodex, Sarcoptes, Dermaleiclnts Anal-
(jes, Oamasus, Ixodes.
Parasitic on plants. Tetranyehus, Phytoptus.
cd into praa-
ingin poison-
api)endages ;
thus.
tTerentiated ;
iiinal appon-
aj : first pair
<, Chernes.
e segments ;
minal spine ;
into trachea\
bdomcn sog-
iiall segments
ps leglike or
; first pair of
us.
Bntiated and
leglike ; one
ining-glands.
lophthalmus,
;hree pairs of
openings of
Dt fused with
ike.
opening into
, the anterior
terior one or
, Theridiniii,
3ndages, anil
3CS long uml
present as a
LITERATURE.
GENEIIAL.
H. Grenacher. Unterauchunge7i iiber das Sehorgan der Arthropoden. GC.ttingen,
^' ^uT^T.xi'"'''^''" ""^ ^'■"'^' ''^- ^'"^'■^^'•'^ J"""-"- Microscop. Sci-
vIKC, A-XI, loo J..
J. Macleod liecherckes sur la structure el la signification de I'appareil respira.
toire des Amchnides. Archives cle Biologic v 1884
^' 'wTc^rix^tso?''"''^'"*''' '^''' ^'•"'''"^"^^«' '^'''"^'^^ a- ^- Zoolog. Inst.
J. S. Kingsley. The Embryology of Limulus. Part II. Journ. of Mor-
phology, VIII, 1893. ^^^*^*
BCOIJPIONIDA.
1. Dufour. Ilistoire cmatomique et physiologique des Scorpions. Memoirs
Aciid. Sciences. Paris, xiv, 1856. ^tuiuiis
E. K^I;anke8ter. On tkeCoxal Glands of Scorvio, etc., and the Brick-red
^^l^ndsoJUmulus. Proceedings of the Royal Society, xxxi v. 1884.
G. H Parker. Ike Eyes m Scorpions. B.llctiu of the Museum of Compar-
ative Zoology, XIII, 1879. v^umpar-
W, Patten. The Origin of Vertebrates from Arachnoids. Q.mrterly Journal
of Microscop. Science, XXXI, 1890. J -Jouinai
M. Laurie. The Embryology of a Scorpion {Euscorpius itaiicus). Q.mrterlv
Jouiu. Microscop. Science, xxxi, 1890. V£<"iutriy
rSEUDOSCOKPIONIDA.
A. Croneberg. Beitragzur Kennt7riss des Banes der Pseudoscorpione. Bulletin
hoc. Imp. Nuturalistes Moscou, ii, 1888. -tsu'ittm
SOLIFUG/E.
1. Dufour. Anatomic, physiologic, et histoire naturelle des Galeodes. Me-
moires Acad. Sciences, Paris, xvii, 1858.
niALANGIDA.
^ wisf ■ 1 T7' '"' t"''"""'' '^"' ^^^^^^^^'mlen- Zeitschrift fur
\\issensch. Zool., XXX VI, 188:2.
i
'SUM..
%*
^
w
IMAGE EVALUATION
TEST TARGET (MT-3)
/
O
1.0
I.I
1.25
■ 45
110
^ 1^ 12.2
IT 1^4
1^ IIIIIM
18
U_ IIIIII.6
6'
%^
n\
■li^
^
6^
^Lfc^'^
C/j
^
mm
460
INVERTEBRATE MORPHOLOGY.
C. M. Weed. A Descriptive Catalogue of the Harvest- spiders (Phalangiida) of
Ohio. Proceedings United States National Museum, xvi, 1893.
2;-«
ARANEiE.
E. Zeyserling. Die Spinnen Amerikas. Nttruberg, 1880-91.
G. W. and E. 0. Peckham. North American Spiders 'of the Family Attidm.
Transactions of the Wisconsin Acad. Sciences, 1888.
H. C. McCook. American Spiders and their Spinning Work. Philadelpliia
1889-90. '
J. H. Emerton. Papers in tbn Transactions of the Connecticut Academy vii
1889, and viii, 1891.
0. Marx. Papers in tlie Proceedings of the Entomological Society of Wasli-
iugtou, 1891. and iu the Proceedings of the U. S. National Museum xii
1890. ' '
W. Sohimkewitsoh. Etude sur Vanatomie de I'Epeire. Annales des Science*
Naturelles, 6meser., xvii, 1884.
Ph. Bertkau. Ueber den Verdauungsapparat bei Spinnen. Archiv. fUr mi-
krosliop. Anatomie, xxiv, 1885.
Bcitrage zur Kenntniss der Sinnesorgane bei Spinnen. I. Die Augai.
Archiv fUr miliroskop. Anatomie, xxvii, 1886.
£. L. Mark. Simple Eyes in Arthropods. Bulletin Museum of Comparative
Zoology, XIII, 1887.
A. T. Brace. Observations on the Embryology of Insects and Arachnids
Baltimore, 1887.
ACARINA.
0. Haller. Zur Kenntniss der Tyroglyphen und Verwandten. Zeitscbr. fiir
wissensch. Zoologie, xxxiv, 1880.
H. Henkingr. Beitrdge zur Anatomie, Entwicklungngeschichte and Biologic roii
Troinbidium fuligiiiohum. Zeitschr. fUr wissensch. Zoologie xxxvii
1882. " ' ■
A. D. Michael. British Oribatidm. Lond(;n, 1984.
A. Nalepa. Anatomie der Phytopten. Sitzungsber. Akad. wissoiisch Witii
xcv, 1887.
W. Winkler. Das Ilerz der Acarinen nebst vergleichenden Bemerkungen uber
das Ilerz der Phalangiden und Chernetiden. Arbeiten a. d. zool Ins
Wien, VII. 1888.
Anatomie der Oamasiden. Arbeiten a. d. zoolog. Inst. Wien vir
1888.
APPENDIX TO THE \UACIINIDA.
There are three orders which show a certain amount of
affinity to tlie Ar-ichuida, but which are not so ch).sely reiatid
as to warrant the actual association of them with the orders
which have heen assigned to that tvpe. They will be de-
lih
TYPE ARACHNID A.
461
Zeltscbr. fiir
L'nsch. Willi,
i
scribed here, and are the orders of the Fentastomidce, the
Pycnogonida, and the Tardigrada,
Order PentastouidsB.
The PentastomidsB are all parasitic, living in the adult
stage in the lungs or nasal cavities of various animals, one
species, PentoMomum tcenioides, occurring in the nasal cavities
or sinuses of dogs and Avolves, VAhile several species have been
found in the lungs of different sptcies of snakes (Fig. 211).
They are all elongated wormlike forms, some-
times slightly flattened and usually distinctly
aunulated, the annuli, however, not repre-
senting a metamerism. The anterior end of
the body is rounded and bears on the ventral
surface the mouth, upon each side of Avhicli
is situated a pair of strongly-recurved hooks
{h) supplied with special muscles and serving
for the attachment of the animal to the tissues
of the host. With the exception of these
hooks no appendages are present.
The body is covered by a cuticle secreter"
by the ectodermal cells (hypodormis), be-
neath which lies a layer of circular muscle-
libres, and beneath these again a lnyex of
longitudinal muscles. The coelom is ample
and is traversed by dorso-ventral muscle-
bands, which divide it into a central com-
partment containing the various organs, sus-
). ended by mesenteries, and two lateral ones. ;„„,^ Femalr .after
lliere is no heart or circulatory apparatus, spkncbr).
and trachefP or othor respiratory organs are '* "^ Jiooks.
also wanting. ^" = *^«"'^''' "••^^'■«-
The digestive tract is a straight tube extending through
tlie body from the mouth to the terminal anus, giving off uo
lateral diverticula throughout its course. The nervous sys-
tem (Fig. 212, wo) consists of a ganglionic mass lying below
tlib (imophagus, a c<)m})aratively small commissural ring
passuig round that portion of tlie digestive tract, without,
Fm. %n. — Penta-
Htomu7,i teretiusru-
ISWu.
462
INVERTEBRATE MORPHOLOGY.
however, possessing any ganglionic enlargement which can
be termed a cerebrum. Various nerves are given off from
the mass, two of which extend backwards throughout nearly
the entire length of the body. The only sense-organs pres-
ent are a number of small papillee on the anterior portion of
the body, which are probably tactile in function.
Glandular organs are highly developed. Scattered over
the surface of the body are numerous flask-sliaped glands
apparently ectodermal in origin, while lying in the coelom on
each side of the mid-gut and extending back almost to the
posterior ena of the body are two long c^cal tubes, a glan-
dular structure being also connected with them anteriorly
These glands open in the vicinity of the hooks and have
hence been termed the hook-glands (Fig. 211, hg), and it has
been suggested that they secrete a fluid which serves to keep
the blood which the parasite ingests from coagulating, being
thus similar to the glands in the pharynx of the Leeches
Fig. 212.— Diagham op Structuhe op Femat,e Pentnstomum (after Spenkcb).
go = genital orifice. od = oviduct.
hff = hoolc-glaiid. ov = ovury.
I = intesliue. j-g = seminal receptacle.
ng = nerve-ganglion. ut = uterus.
which serve the same purpose. Unless the eciodermal glands
are excretory, no special organs for the carrying on of that
function occur.
The Pentastoniidre are bisexual, the mule being smaller
than the female, aud recognizable l)y the situation of the geni-
tal orifice (Fig. 211, 70), which is near the anterior end of the
body, wljilo in t\w female it is near the posterior end. The
ovary and testis are both uii])aired organs situated beneath
the dorsal surface of the body and extending almost its eutiro
length. Anteriorly a pair of oviducts (Fig, 212, <)\Mmng Pentastomum to be related to the
Arachnids is the occurrence of the four-legged larva, which resembles so
tar as Its external form is concerned, a Mite. The internal structure is
\ my different, however, although corfain Arachni.l features are indicated ■
I'ut It IS evident that the.se forms must have undergcu.e an enormous de-
l-amire from the ancestral form during which the remaikal)le life-historv
an.l peculiar structure have been acquired. The parasitic habits of many
liu-s. and the general similarity of tiie body form of Demmlex to that of
I'Htastom.im, suggest the Mites as the ancestors of the latter, a theory
wlacii IS as plausible as any other which can at present be suggested.
Order Pycnogonida.
The Pycnogonida are exclusively marine in habitat, and
vary considerably in size, the smaller forms, such as Tamjsty.
It
Ml'
«...
'X i
464
INVERTEBRATE MORPHOLOGY.
lum, being only about a millimetre in breadth, while the
purple Fhoxichilidium measures over three millimetres from
tip to tip of the legs, and the deep-sea form CoUossendeis has
a span of over sixty centimetres. The body proper is compar-
atively small, the four pairs of long legs which arise from the
thorax being exceedingly conspicuous, a feature which has
Fig. 213. — Phoxichilidivm mnxillare (after Morgan).
suggested the term Fanfopoda sometimes applied to the
group. An'oriorly there is a ivell-marked proboscis carrying:;
the mouth at its anterior end, and at the base of this there
arise the cheliceriB, which are rather short chelate limbs.
The next segment of the body succeeding that which bears
the cheliceru} bears upon its dorsal surface the eyes, and may
be regarded as a fusion of three segments since it bears three
pairs of appendages. The most anterior of these are slender
'
TYPE ARACUNIDA.
465
jointed palps; the econd pair, wautiug in the females of
some species, but always present in the males, arise from the
ventral surface of the segment, and are curved jointed struc-
tures serving to carry the ova ; while the third pair are ex
ceeding long jointed walking-legs. The next three segments
nlso bear long walking-legs, the last one having attached to
it the usually unsegmented rudimentary abdomen.
The body and the appendages are encased iii a well-de-
veloped chitinous cuticle, and there are no indications of
special respiratory organs. The heart lies immediately be-
neath the dorsal integument and is a simple tubular organ
with from two to three pairs of ostia.
The portion of the digestive tract which lies within the
proboscis is lined with chitin and opens behind into an
elongated mid-gut, from which long diverticula extend out into
the chehceraa and the proboscis and into the walking-legs
sometimes reaching even into the terminal joints of the latter'
A short hind-gut leads to the anus at the tip of the abdomen
The nervous system consists of a supracesophageal gan-
glionic mass, from which arise the optic nerves and those for
the chehcerae, as well as certain nerves passing to the pro-
boscis. Connected with this brain by circumoesophageal com-
missures IS a ventral chain consisting of five pairs of ganglia
the first pair of which is really formed by the fusion of two
pairs, distinct in the embryo, and innervates the palps and the
oyigei-ous legs, while the four pairs of walking-legs are sup-
phed by the remaining four pairs. Finally one or two small
guugha also occur, innervating the abdomen. The eyes are
imir in number, situated at equal intervals upon a small
(lomelike elevation on the dorsum of the first thoracic seg-
ment, which, it is to be remembered, is compound. Each eye
IS covered by cuticle, sometimes thickened so as to form a
lens, below which is a layer of cells forming the corneal or
cuticular hypodermis. Below this comes a thick layer com-
posed ot retinal elements with nuclei in their outer portions
and rodhke bodies towards the inner ends where they rest
iil)on a layer of pigment. ,
Tlim' eyes recall the poslbacillar eyes of tl.o Arachni.ls by their struct-
me, but show one renmrkable peculiarity, i.e., a distinctly bilateral ar-
^mmmm
466
IN VERTEBRA TE MORPHOLOO T.
P?
,««• nil
rangement both of the corneal hypodermis and of the retinal elements, a
distinct raphe being observable upon the inner surface of the eye, the reti-
nal elements being arranged on either side of it. Such a condition as this
cannot readily be explained by a simple unilateral invereion such as was
described as probably occurring in Arachnidan eyes; it suggests rather an
invereion of two sides of a primitive optic cup, the posterior wall at tlio
same time forming the pigmented layer of the eye. "Whether the Arachnid
eye is not also traceable to such an arrangement, all traces of the original
raphe being lost, is a question, though at present it seems more probable
that it has been produced by a suppression of the inversion of one side of
the cup.
Glands, occurriag in the palps and ovigerous legs, have
been regarded as excretory in function, but no Malpighiuu
tubules or coxal glands seem to exist, though an homologj- of
the excretory glands just mentioned and of glands occurring iu
the walkiug-legs of the males with the latter is not impossible.
The Pycnogonids are bisexual, the reproductive organs lying
in the thorax and sending out branches into the walking-legs,
on the fourth joints of one or more of which they open. As
already stated, the male carries the eggs upon his ovigerous
legs, fastening them as they are extruded by the female by
means of the excretion of the gJauds occurring upon the
walking-legs.
Development and Affinities of the Pycnogonida. — The young Pyciio-
gonid leaves the egg as a six-limbed embryo, which recalls, in a general way.
the nauplius of the Crustacea, and indeed has suggested a derivation of
the Pycnogonids from that group. The resemblance is, however, but
superficial, important differences being found in the structure of the eyes
and in tiie absence of an anus, to say nothing concerning the details of the
early development. On the other hand these last, as well as the structure
of the eyes, recall the Arachnids, and it seems most probable that the
Pycnogonids are to be regarded as having descended from ancestors wIiIlU
might have been included in the type Arachnida.
Order Tardigrada.
The Tardigrada are small forms not exceeding a milli-
metre in length, with an uusegmented body provided with
four pairs of short conical appeudages tipped with claws, tiie
last pair being situated at the posterior extremitj- of the body.
The body is covered by a cuticle secreted bj' the subjacent
hypodermis, below which and traversing the coelom is a well-
TYPE ARACHNID A.
467
developed system of muscle-bands. There are no special
organs either for respiration or circulation.
The mouth (Fig. 214, m), surrounded by papilla, lies at the
anterior extremity of the body, and leads into a tubular
mouth-cavity containing, imbedded in
its walls, a pair of chitinous or partly
calcareous teeth, and receiving the
ducts of two glands {sg) which have
been regarded as salivary or perhaps
poisonous in function. Behind, this
cavity opens into a muscular pharynx
which is connected by a short a3so-
phagus with the mid-gut (s). At the
junction of this with the rectum or
hind-gut is a pair of cfiecal diverticula
{mg\ possibly Malpighian tubules,
and into the hind-gut there also open
the ducts of the reproductive organs,
the hind-gut thus serving as a cloaca.
It opens on the ventral surface of the
body a short distance from the pos-
terior extremity and therefore in front
of the last pair of appendages.
The nervous system consists of a
supracfisophageal ganglion (ce) united
with a chain of four pairs of ventral
ganglia. No special sense-organs occur
except two eyes situated at the sides
of the head. The sexes are distinct,
the reproductive organ being un-
paired and opening into the cloaca,
into which opens also in both sexes
au unpaired accessory gland.
The Tardigrada occur in water usually, especially in such
locations as the gutters on the roofs of houses, though some-
txines found also among moss. The group contains but a
small number of genera, of which Macrohiotus is perhaps the
most common.
Fig. 214. — Diagram op
Stkucture op Macrobiotua
megalonyx (after von Erlan-
oek).
an — iiuus.
ce = cerebral gauglion.
e^— e* =: appendages.
h = bindgut.
m = moutb.
mg = mid-gut diverticula.
oc = eyv.
a = midgut.
iff = salivary (?) glands.
so = suboesopbageal gan-
glia.
468
INVERTEBRATE MORPITOLOOT.
«3 lis
2 "5
Affinities of tlie Tardigrada.—ThQ presence of four pairs of limbs has
usually been regarded as pvMnting to a relationship of these forms with tho
Acarina, but the absence of all mouth-appendages, the structure of the
legs, and the position of the last pair with regard to the anal opening, not
to mention the peculiarities of the internal organization, are opposed to
any close relationship with the Arachnida. The Tardigrada must be con-
sidered as holding an independent position, without distinct indications of
relationship with any of the types, until further information as to their
primitive relationships has been secured. In addition the embryological
history, which has recently been worked out, furnishes no evidence in favor
of Arachnidan afiflnities, and it seems quite probable that the Tardigrades
should be removed entirely from among the Arachnida and possibly
associated with such forms as the Echinodera.
LITERATURE.
PKNTASTOMIDA.
B. Leuckart. Bau und Entwicklungsgeschichte der Pentastomen. Leipzig uud
Heidelberg, 1860.
C. W. Stiles. Bau und EntwicklungsgescMchte von Pentastomum pi'ohosddeum
und P. subcylindrictim. Zeitschr. flir wissensch. Zoologie, Lii, 1891.
A. B. Spencer. 17ie Anatomy of Pentastomum ieretiusculum {Baird). Quar-
terly Journal of Microscop. Science, xxxiv, 1892.
PYCNOGONIDA.
I. B. Wilson. The Pycnogonida of Neto England and Adjacent Waters. Re-
port of the U. S. Commissioner of Fish and Fisheries for 1878. Wash-
ington, 1880.
A. Dohrn. Die Pantopoden des Oolfes ton Ncapel. Fauna und Flora des
Golfes von Neapel. Monographic, in, 1881.
P. P. C. Hoek. Report on the Pycnogonida. Scientific Results of the Voyage
of H.M.S. Challenger. Zoology, iii, 1881.
T. H. Morgan. A Contribution to the Embryology and Phytogeny of the Pycno
gonids. Studies for the Biol. Laboratory, Johns Hopkins University, v,
J891.
TAIIDIGKADA.
X. Plate. Beitrdge zur Naturgeschichte der Tardigraden. Zoolog. JahrbUcher,
Anatom. Abtheilung, iii, 1888.
E. von Erlanger. Beitrdge zur MorpJiologie der Tardigraden. Morpholog.
Juhrbuch, xxii. 1895.
TYPE TB ACHE AT A,
469
CHAPTER XV.
TYPE TRACHEATA.
The Tracheata are, like the Araclmida, essentially terres-
trial forms, for, though a few Insects have adapted themselves
to an aquatic mode of life, they are nevertheless air-breathers,
living either at the surface of the water or coming to the sur-
face from time to time to renew the air contained in the
tracheae which ramify through the body and serve as respira-
tory organs. However, a few Insect-larvse have acquired the
power of extracting oxygen from the water by branchia-like
processes of the body, but, even in these cases, trachero form
the organs by which the respiration is carried on, the branchi^
being richly supplied with them.
The body is distinctly segmented (except in Peripahis,)
and is covered by a chitinous cuticle secreted by the ecto-
dermal cells, which constitute the so-called hypodermis. The
appendages are usually uniramous, and with few exceptions
{Peripatus) are jointed. The anterior pair in all cases are
more or less elongated multiarticulate structures provided
with sense-hairs, and are situated prajorallv, while of the
remaining pairs, varying in number in different groups, the
most anterior pair is specialized to serve as mandibles, while
the succeeding one or two pairs usually form maxillte. Numer-
ous glands of varying function are developed in the hypo-
dermis, the most interesting of which are the crural glands,
well developed in Peripatus, and represented more or less
perfectly in certain other forms. In addition to these, glands
which secrete an acrid or offensive fluid {repugnatoricd glo.nds)
are frequently present, as well as others which secrete waxy
substances, or even in some cases silk.
The coelom except in Peripatus is lacunar throughout, pos-
sessing no definite walls, and is traversed in various directions
by muscles, serving to flex or extend the body and to move
i»
»
IN»'
i^«p«i«1
470
INVERTEBRA TE MORPHOLOQ Y.
«£ llM
I '}
the appendages. A marked difference between the Tracheata.
and the Arachnida is the universal absence of an endo-
sternite, a structure of considerable phylogenetic significanco
in the latter group. A heai't is invariably present, lying
above the intestine, and situated in a pericardial sinus incom-
pletely partitioned off. In the major.ty of forms the parti-
tion is composed of a varying number of triangular muscles,
the alar muscles, which are attached by their bases to the
walls of the heart, and by their apices to the body-wall.
While at rest they are somewhat vaulted, the convexity being
dorsal, and on contraction flatten down, thus enlarging the
sinus and causing a flow of blood into it. The heart (Fig.
227, h) is elongated and imperfectly divided into a series of
chambers, separated by pairs of valves which allow the blood
to flow from behind forwards but not in the reverse direction,
the heart being closed behind. Ostia are present in the
lateral walls to allow of the entrance of blood into the heart-
chambers, whence it is propelled through very short arteries
which open widely into the lacunar spaces of the ccelom. In
many forms a central sinus surrounds the ventral ganglionic
nerve-chain, the blood flowing in it from before backwards,
but with this exception definite vessels are wanting. This is
compensated for by the rich branching of the tracheae, which,
as stated, serve as respiratory organs and convey air to all
parts of the body ; the air is in fact brought directly to the
tissues, instead of being carried to them by the blood from
limited portions of the surface of the body. The bbod is
usually colorless, but in some cases is of a bright yellow or
green color, owing to pigment contained in the plasma, and it
contains in all cases colorless amceboid corpuscles.
The tracheae (Fig. 215, tr) communicate with the exterior
along the sides of the body by a varying number of pairs of
stigmata {st), and may either consist of bunches of unbranched
tubes connected with each stigma, or of a number of richly-
branching tubes, each one arising from a separate stigma and
anastomosing in some cases through some of its branches
with the tubes from other stigmata. Each stigma is usually
provided with an apparatus by which it may be closed, ami
in the Insects the air is expired from the tracheae by the ecu-
isS'
TYPE TRACHEATA. 471
traction of certaiu dorso-ventral muscles of the abdomen
which cause a compression of the organs in that region of the
body inspiratioL following on their relaxation and the conso-
quent re-expansion of the abdomen. In structure the trachea
are simply to be regarded us invaginations of the body-wall
aud consist of a single layer of cells continuous with the hypo!
dermis of the body, lined within ^^
—that is to say, on the surface
with which the air is in contact
—with chitin, which is thick-
ened in such a way as to form
a spiral band extending along
the tube and serving as a spring
to keep its walls apart.
The digestive tract is in
most groups a straight tube,
but in Insects (Fig. 227) it may
be coiled in a more or less com-
plex manner and differentiated
into several parts. Glands of
various kinds are usually asso-
ciated with it, salivary glands
(Fig. 227, sg) opening into the
anterior portion and Mulpighian
tubules {inv\ in connection with
the posterior portion, being
the most constant in occur-
rence. It is to be noted that
the fore-gut and hind-gut are
ectodermal in origin, and that
the Malpighian bodies arising
as outgrowths from the hind-
gut are also ectodermal, differing
thus in origin from the similarly-
named organs of the Arachnida, which are apparently of
eudodermal origin, arising from the mid-gut. In function
both orgaus are similar, the Malpighian bodies of Tracheates
being excretory.
The nervous system in the less-differentiated members of
Fig. 315. — Figure showing the
D18TKIBUT10N OP Trachea in
Aylm pelargonii (after Witlaczil).
At = antennse.
g = glaud-duct.
St = stigma.
tr = trachea.
1, 3, 3 = thoracic appendages.
h !'
I \
472
INVERTEBRATE MORPHOLOGY.
the type consists of a siipraoesopliageal ganglionic mass, con-
ncs.ted by circumcBsophageal commissures with a chain of
ventral ganglia, a pair of ganglia corresponding typically with
each segment. In the Insecta (Fig, 228) more especially,
however, considerable concentration occurs, a number of the
})ostoral ganglia, or, in some cases, all of them, fusing to a
single mass. A well-developed stomatogastric or sympathetic
nervous system occurs in all forms, arising from the supra-
uisophageal ganglionic mass by two trunks, which unite to
form a single nerve, passing to the digestive tract, and in
some cases provided with ganglionic enlargements both
paired and unpaired.
Sense-organs of various kinds are well developed in the
Tracheata, with the exception of Peripatus, in which the
only definite orpaus of special sense are the eyes. In other
forms the antenna and other portions of the bodv are pro-
vided with hairs connected with nerves and serving as tactile
organs, and seta) situated upon the mouth-})arts and associated
with peculiar nerve-endings have been supposed to represent
organs of taste, and others again, on the antenuje, olfactory
organs. Eyes .are very generally present. In Peripidns ami
most Myriapoda simple ayes or ocelli are alone present ; in
l*evipatus they resemble closely in structure the eycK of the
Annelids or Mollusca (e.g. Ilalioiis, see Fig. 134), but in the
Myriapods and Insects they are usually more complicattnl.
Tims in a young larva of AciUm (Fig. 216, A\ a water-
beetle, the chitin is thickened to form a cornea (J) whicli lies
over a depression of the liy^^oderMiis, the cells at the bottom
of which are modified to form a retina, each being contiuuoiiH
at its inner end with the optio nerve (7t), while at its outer
end it bej-rs a layer of chitin (/). The cells of the lip of tlio
depression have ';onverged together h".' as to meet beneatli the
cornea, which is indeed formed by those cells, and a cavity is
tlius enclosed into which theio i)r(.trude from among tli«
retinal cells largo c^lls {rmje) with chitin dejiosited on tiicir
adjacent siirfaces. In a hitev sti'.ge (Fig. 21(5, II) the lij)s of
the dopreK;:ion have unitevl, a continuous corneal liypoderiiiis
[vh) being thus jjrodiu'ed ; pigment lias been deposited in the
lateral cells, and the ictiinil cells, i)ig!heuted near their outer
TYPE TRACHEATA.
473
eud8 and in continuation witii the optic nerve, have developed
distinct rods (r) at their outer ends.
In the Insecta and cccasionally in the Myriapoda (Scuti-
gera) there are m addition to these simple ocelli compound
eyes situated at the sides of the head and similar in structure
to the compound eyes of the Crustacea. Each of the .m-
luatidia of which the eye is composed, and tlere may be
F,G. 216.-8ECTIONS THKOaon AN OCELLUR OF A LaUVA OF ^.wJ'l^N {A) A
Veuy loUNG AND IN (B) AN OLDEIi iSPECIMKN (after Pxtten)
ir = inverted rods. ,, = ^erve
' = '"";!^'''- Pff = pigment.
mgc = niedjiiu gliint cells. r = rods.
vb = vitreous body.
8.v( >al thousand of them in each eye, conftists of an external
cornea (Fig. 217, ro), usually more or less hexagonal in outline
giving the eye a faceted appearance. Beneath the covuoa
iUB two cells which secrete it and form the corneal hypo,l,n-
"lis, and below these again come four cells, the crystallinp-
ou.u, cells, which may (emonom eyes) or may not (acmn.s
oyes) manufacture a crystalline cone (c\ and finally 1 eneath
tliose IS a circiG of seven retinular cells (four in Zepmna)
t'ucj one of which is pigmented and manufactures a portion
jf the chitinlike rhabdoni (rh) whicli th
cell,"'
are i)robably contiisuous at their inner
ttiFwujiu j blltise
ends with the
optic nerve. Additional pigment-cells {pg) separate the
•i
i
lil V
474
INVEBTEBRA TE MORPHOLOO 7.
various ommatidia.
CO
pg'
Rh
Pg*"
T
Fig. 217. — Ommatidium
OF Eve of Munca (after
HiCKBUN).
c = crystiiUiue coue.
CO = c'onieii.
Pff = piijint'iit cells.
r = retiimlii-ceUs.
Bh = rlmlHloia.
T = tiacheii.
tv = tmchctil dllutatioD.
Other sense-organs occur in the various
groups, but may more satisfactorily be
considered in the special descriptions
of these groups.
True nephridia similar to those of
the Annelids occur in Peripatus, but iu
the Myriapods and Insects they are en-
tirely wanting, their place as excretory
organs being taken by the Malpighiau
tubules. The Tracheata are bisexual,
the reproductive organs being typically
paired and opjning to the exterior by
ducts, which may unite before reachiiij^
the genital orifice. Accessory struc-
tures, such as a bursa copulatrix for
the reception of the penis and a recep-
taculum seminis occur iu the female, ami
vesiculiB semiuales and accessory glands
in the male. The region of the body-
wall in the viciuit}' of the reproductive
orifice is in the Insects frequently iu-
vagiuated, adding a still greater com-
plication, and furthermore the terniiual
portion of the duct in the male is
frequently capable of being evaginated
and thus serving as a penis, while
integumentary elevations or processes
of the last abdominal segment iovm
ovipositors in the females.
I. Clash Protraeheata.
This interesting group contains but a
single genus, Pcripntm, which has, lii>u-
ever, a wide distribution, species Ixiiij,'
found in tne West Indies and South Anu'rica, at the Capt' of
Good Hope and in New Zealand, thus indicating an origimd
wide distribution of the genus which has become extinct
except iu these few widely separated regions.
Feripiitm is an elongated cylindrical form, measuring iu
TYPE TR ACHE AT A.
475
jraeut form
the Cape species (Fig. 218) from about five to six and a half
centimetres in length, and is found beneath stones or bark o-
amongst decaying wood. The body -wall is finely annulatedi
the annuli not, however, corresponding to segments, and the
cuticle is thin, small papillae being scattered all over the
surface of the body, each terminating in a short bristle
The head is but poorly marked off from the rest of the body
and bears a pair of many-jointed anteunje, at the base of each
of which towards the sides of the head is situated an eye. The
mouth lies in the middle of the ventral side of the head and
IS surrounded by t umerous papilla?, and within its cavity is
situated a pair of jaws furnisljed with strong chitinous sickle-
shaped teeth. These jaws really represent the second pair of
Pig. 'i\9—Penpatm capensis (after Moseley from Balfour).
appendages, the third pair being represented by two short
papillsB lying at the sides of the head and having at their tips
the openings of a pair of glands which extend far back into
the body-cavity and from which, when tlie animal is irritated
there is violently emitted a sticky fluid, whence the glands
have been termed the slime-glands (Fig. 219, s(i). There is
IK) division of the trunk into thoracic an ..bdomiual regions
and It bears a number, varying according to the species from'
seven to twenty-one pairs, of ambulatory appendages, each of
which consists of a proximal stouter and somewhat conical
portion bearing rings of papillae and a more slender short
distal portion which bears at its tip a pair of claws (ungues).
Ihese limbs are unsegmented, differing in this respect from
those of the Myriapods and Insects, and are also soft owing
to the thinness of tlie cuticle, a feature wliich has suggested
thfl name Mnlampixla formerly api.lied to the tyne, as the
presence of the terminal ungues has suggested 'the term
(hnfvhophom. The anus is situated at the posterior extremity
Ox the boaiMs (F^K- ^20)» and is lined throii^'h-
out by a peritoneal epithelium
which covers the various or-
gans. From it are, however,
separated certain cavities with
detinite walls, which staud in
relation to the nephridia and
the reproductive organs ami
will be spoken of in connection
with these organs. A heart
(Fig. 220, h) of a tubular form
extends throughout almost the
entire length of the body,lviiig
oc) incompletely separated
fenestrate
(from Hkbtwio).
a = anus.
ai = nnteuniB.
ftwt = ventral nerve-cord.
d = inlostiiie.
go = opening of reproductive organ.
0 = ovary.
og = brain.
p = ))liarynx.
sd = slinic-glands.
80 = nepliridia.
sp = salivary glands.
tr = trachea).
M = uterus.
in a pericardial space (Fig. 220
from the rest of the ccjelom by
rausverse par-
Ik
13-
!■
TYPE TRACHEATA.
477
tition. A pair of ostia are situated on the dorsal surface of
the heart in each metamere, aud pass the blood into the heart
from the pericardial space. Respiration is performed by
trachesB (Fig. 219, tr) consisting of slender unbranched tubes
which arise in bunches from stigmata, either scattered ir-
regularly over the surface of the body in considerable
numbers or else arranged, as in P. capemis, somewhat imper-
fectly in two rows upon the dorsal and two on the ventral
surface of the body.
The mouth opens into the mouth-cavity containing the
mandibles, and this communicates posteriorly with a muscu-
lar pharynx, and has opening into it the ducts of two long
tabular salivary glands {sp) which extend through more than
half the length of the body. The pharynx (p) communicates
by a short oesophagus with the stomach, which extends as a
straight tube almost to the extremity of the body, where a
short rectum places it in connection with the anus. The
pharynx and oesophagus and the rectum are lined with chitin
and represent the fore-gut and hind-gut of other Tracheates,
the stomach being the mid-gut. No Malpighian tubules or
other diverticula of the intestine occur.
The nervous system shows several highly-interesting
features. There is, as is usual in metameric animals, a supra-
(jesophageal ganglion-mass (Fig. 219, og) composed of at least
two and probably three pairs of ganglia, of which the first
supplies the antenuie aud the second the mandibles, while a
third pair lies at the sides in close contact with the second
pair and sends nerves to the oral papilho. These latter are,
however, postoral and ventral in position, and from them
tluu-e extend back two ventral cords {hm) which in each
iiietauiere dilate into a gaugliouic swelliug. The two ventral
<'<»r(ls are, however, widely separated, lying in the lateral
chauibers of the cojlom (Fig. 220), and are connected by a
liirge number of cross-commissures — a condition which recallH
the arraugemeut in i •, Amphiueurous Mollusca (see Fig.
124), the similarity being further increased by the facts that
the two cords unite behind and above the rectum, as in the
Soleuogastres, aud that the ganglion-cells are not confined to
the enlargements but are scattered all along the cords. Tho
It
478
IN VERTEBRA TE MORPHOLOO Y.
eyes are the only special organs of sense ; their structure has
been already indicated (p. 472).
One of the most interesting features of Peripatus is the
occurrence in it of typical nephridia (Fig. 219, so). Upon the
under surface of the proximal portion of each limb, with the
exception of the penultimate or last pair, there is a slitlike
opening which leads into a more or less coiled tube lying in
the coelomic compartment, which extends into the limb and
Fig. 220.— Transverse Section op a Peripatus (after Sbdowick)
c = central compartmeut of ccelom. mg = slime-glands.
g = reproductive organ.
h = heart.
/ = intestine.
/ = lateral compartment of coilom.
■ju = muscles.
JV = ventral nerve-cords.
ne = nephridia.
p = compartment of ccelom which
extends into the limb.
pc = pericardial compartment of the
ccelom.
terminates in a thin-walled vesicle. These tubes are ne-
phridia, the terminal vesicles (Fig. 220, ne) representing por-
tions of the coelom into which the nephridia open — a fact
indicated by their erabryological history. The nephridia are
thus exactly comparable in every respect with the nephridia
of Annelids, communicating at one extremity with the exterior,
and at the other with th.« coelomic cavity. It i^ interesting to
note that the development of the salivary glands shows that
TYPE TRACHEATA.
479
iructure has
shows tliiit
they are the modified nephridia of the third segment of the
body, that which bears the oral papillse, and furthermore it is
to be noted that in the last or next to last (according to the
species) limb-bearing segment, in which nephridia are wanting,
are found the ducts of the reproductive organs— a fact whicih
suggests that these are also modified nephridia. This idea is
confirmed by the development of the genital ducts, and car-
ries with it the corollary that the cavities of the reproductive
organs (Fig. 220, g) are portions of the coelom, just as they
were shown to be in the Mollusca (see p. 288).
In addition to the nephridia there are associated with cer-
tain of the appendages glands which open on the under sur-
face of their basal moiety and are termed the crural glands.
In P. capemis they are present in all the appendages except
the more anterior one, and the slime-glands are simply the
highly-modified crural glands of the oral papillae, those of
the last pair of appendages in the males of this species being
similarly elongated though possessing a difi'erent function.
In P. Edwardsii, however, crural glands occur only in the
males, and in these only in a few segments immediately in
front of that bearing the reproductive opening.
The Protracheata are bisexual, the female usually being
somewhat larger than the male. The ovaries are paired,
thvmgh included within a common capsule, and lie in the pos^
teiior part of the coelom. They are continuous with two
uteri, which immediately at their origin are united by a trans-
verse tube, and each bears a receptaculum ovorum and a
receptaculum seminis. Beyond this each continues its course
along the side of the body, passing backwards to finally
unite at the common orifice, lying a short distance in front of
the anus on the ventral surface of the body. The testes are
slender paired structures whicli are continuous with a slender
yas deferens. This dilates a short distance from the testis
into a vesicula seminalis and then unites with its fellow of the
opposite side to form a slender somewhat coiled tube, the
ductus ejaculatoriuH, in the terminal portion of which the
spermatozoa are united together into a spermatophore. The
1 rotraciieata arc viviparous.
I
Wlk'
480
INVERTEBRATE MORPUOLOOY.
r<\
i
Affinities of the Protracheata. — Peripatus\& a highly-suggestive form
on account of possessing both Annelidan and Tracheate characteristics, so
that it has been generally regarded as indicating a descent of the Tracheate
forms from the Annelids. Its Annelidan features are, first, the presence of
a distinct dermal muscular system; second, the occurrence of crural glands
wh'ch seem to be homologues of the glands which secrete the set® in the
Annelida; third, the possession of nephridia corresponding closely to those
of the Annelids; and fourth, the structure of the eyes. On the other
hand, its Tracheate aflBnities are shown by the claw-tipped feet, by the
adaptation of the feet (mandibles) for masticatory purposes, by the ten-
dency towards a concentration of the anterior segments to form a head,
and by the occurrence of tracheae. Both these sets of features are highly
important, and, taken with the wide distribution of Peripatus, point
strongly to its being the representative of a connecting link between Tra-
cheates and Annelida, a phylogeny which may be considered more in de-
tail at the close of this chapter.
II. Class Myriapoda.
The Myriapoda possess a distinct head composed of a num-
ber of fused segments and followed by a distinctly-segmented
body formed of a varying number of segments, all of which
are more or less similar, there being no differentiation of a
thorax and abdomen. A single pair of appendages as a rule
is borne by each segment, with the exception, in some cases,
of the last. The most anterior pair are usually long multi-
artic'ilate antennae, the second pair mandibles, and the third
and fourth, or the third alone, are modified to form maxilhi ;
the succeeding pairs, with one or two exceptions, are ambula-
tory, and are jointed and tipped by a claw.
The chitiuous cuticle is generally thick, and consequently
no definite system of dermal muscles is developed, a number
of separate muscles occurring in each segment for moving the
appendages and the various segments u])on one another.
Glands of various kinds opening upon the surface of the btxly
occur, the most important being glands or protrusible gland-
ular sacs situated upon the basal joints of a number of the
appendages and apparently homologous with the crural
glands of Peripatus.
The heart is in all forms verv loner, extendiner tlirnncfli tlie
entire length of the body behind the head, and possessing
I
TYPE TRACHEATA.
481
just as many chambers and pairs of alar muscles as there are
trunk-segments. The number of stigmata vary, in some
forms only a single pair occurring, while in others there is a
pair on each segment of the trunk; and the form of the
tracheae varies also, as they are ciometimes branched and
sometimes arranged in bunches composed of a number of un-
branched tubes.
The digestive tract is almost always a straight tube, ex-
tending through the body to the terminal anus. The mouth
is guarded in front by a well-developed upper lip or labrum,
while the fusion of the maxillse behind it in many forms pro-
duces a lower lip. It leads into an ectodermal fore-gut, and
this into an endodermal mid-gut, which is usually provided
with a number of unbranched diverticula termed hepatic creca.
One or two pairs o{ Malpighian tubules open into the ante-
rior end of the ectodermal rectum, and serve as excretory
organs.
The nervous system except in the head region shows but
little trace of concentration, there being as a rule in each
segment of the trunk a pair of ganglia. The antennal ganglia
are fused with the supraoesophageal ganglionic mass which
sends off branches to the ocelli ; these may be quite numer-
ous, though compound eyes do not as a rule occur. A sympa-
thetic system is present as in other Tracheates.
There are no nephridia so far as known in the group, the
excretion being performed by the Malpighian tubules. The
reproductive organs are paired, and open to the exterior in
some cases by paired orifices, but more usually by a single
opening, which may be situated either far forwards, or else
in other cases near the posterior extremity of the body.
»
It
irouch flie
1. Order Pauropoda.
The order Pauropoda contains a few small forms in which
the trunk possesses twelve metameres and but ten pairs of
appendages, which, with the exception of the rudimentary first
pair, are six-jointed and terminate in a claw. When viewed
from the dorsal surface, the segments appear to be less nu-
merous than the appendages, a condition which results from
48d
INVERTEBRA TE MORPEOLOO Y.
Fig. 221. — Pauropus
tlie fusiou of certain metameres iu pairs, so that two pairs of
appeudages appear to belong to some of the segments, the
double nature of which is further shown by
the occurrence iu them of two pairs of
nerve-ganglia. The antenna) (Fig. 221) are
remarkable in form, consisting of a four-
jointed basal portion which bifurcates at
the tip, one of the bifurcations bearing two
long liagella and a peculiar spherical
stalked body, while the other one bears a
single flagellum. Mandibles are present,
and there is also a single pair of but poorly-
developed maxillae.
Tracheae or other respiratory organs are
'suxkyHtrom'hzvyilh ^ot yet known to exist, nor have any in-
dications of a circulatory system been dis-
covered up to the present. The reproductive opening is
situated upon the second trunk-segment.
None of the members of the order exceed a little over a
millimeter in length. The genus Pauropus i^ characterized
by the body being elongated and cylindrical, and by its active
movements, while in Eurypauropus the body is flattened and
relatively broad, and the movements are sluggish.
3. Order Diplopoda.
The Diplopoda, sometimes termed the Chilognatha, are
popularly known as the Millipedes on account of the commoner
forms possessing an unusually large number of appendages.
The body is usually cylindrical and provided with a hard
cuticle, and many forms are in the habit of rolling themselves
when disturbed into a ball or a helixlike coil, thus protect-
ing the more delicate ventral surface of the body. The an-
tennae (Fig. 222, at) are generally seven-jointed and are never
very long, and the mandibles are strong jaws without pulps.
In front of the mouth is a well-developed upper lip (ul), while
behind it is a lower lip formed by a fusion of the maxillte (nix).
According to some authors this lower lip represents two pairs
of appendages, but its innervation and embryological history
seem to be opposed to this view. The segments behind the
TYPE TRACES AT A.
483
head vary in number in different genera from eleven {Glo-
meris) to over one hundred, and the number of appendages is
much greater still, since the majority of the segments bear
two pairs of limbs and in reality represent each two meta-
raeres. The four or five anterior trunk-segments are, however,
single, bearing but a single pair of limbs (Fig. 222), and one
of them — in some cases the
first, in others the second, but
more usually the third (lulus) —
is entirely destitute of appen-
dages. The last few segments
also carry but a single pair of
appendages, as does also the
seventh segment in the males,
the appendages of which are
usually modified to serve as
copulatory organs.
Stigmata occur on each of
the trunk-segments, the double
segments bearing two pairs,
situated on the ventral surface
near the coxal joints of the
limbs. Each one has in connec-
tion with it a bunch of un-
branched tracheae, a condition
recalling somewhat that of Peri-
patus, although the location of
the stigmata is much more regular and definite. Upon the
dorsal surface of the body there is in most species a row of
pores which have been mistaken for stigmata, but are really
the openings of glands (gl repugnatoria) secreting an oily
evil-smelling fluid which serves as a means of defeuca. In
the genus Polydesmus the secretion contains hydrocyanic
acid. Crural glands do not as a rule occur, but protrusible
warts occurring on the coxal joints of a number of legs in
some genera {Lysiopetalum) have been regarded as homolo-
gous structures.
Tlie nervous system has the cliaraftteristic Myriapodan
arrangement, each of the double segments possessing two
Fig. 232.— Anterior Portion op a
DiPIjOPOD.
at = antenna.
cop = copulatory appendages.
mx = maxilla.
ul = upper lip. [segments.
1, 2, 3, 4 = the four anterior trunk-
\t
484
INVERTEBRATE MORPHOLOGY.
iSi
*• 11
pairs of ganglia. Eyes are usually present and are always
simple, varying in number from two to as many as eighty.
The Diplopoda are bisexual, and the ovaries or testes form
a single mass from which two ducts, or one which later
divides into two, arise and pass forward to open on the ven-
tral surface of the body between the second and third trunk-
segments. The embryos when first hatched out possess but
three pairs of legs, situated upon the first, third, and fourtli
segments in Strotigylosoma, and on the first, second, and fourth
in Iidus, one or more segments without appendages lying
behind the fourth pair. By successive moults new segments
and appendages are added and the form of the adult gradu-
ally acquired.
The Diplopoda live for the most part under stones, etc.,
or among dead leaves, and find their food in decaying vege-
table matter, though some forms will attack living vegetation
and may prove thereby injurious to gardens. The commonest
form, Iidus, may readily be obtained under stones or boards
all through the summer.
3. Order Chilopoda.
The Chilopoda, or Centipedes, are very different in their
habits from the Millipedes, being carnivorous and provided
with poison-glands which render the larger forms of iScolo-
pendra dangerous even to man. The body is as a rule some-
what flattened and less hard than that of the Diplopoda.
The antennae (Fig. 223, at) are usually long, with at least
twelve joints, and may be as long as the body, while the
mouth-parts are much more complicat * than in the Dip-
lopoda. The mandibles and upper lip ve.f n^vie the c '''r,;-
spouding parts in that group, but the mavillsB {mx) are jaw-
like, are not fused together, and in some forms (Geophihis)
bear a palp. Behind the maxillfe comes a pair of second
maxillse (mx^), which, however, do not serve as jaws but are
TtaCvUved to a pair of palplike structures, and behind these again
iz u. pirir of maxillipeds (mxp), the appendages of the first
trunk-segment, with their basal joints fused to form a lower
lip supporting a four-jointed palp, the last joint of which is
Hi
TYPE TRACHEATA.
485
Fig. 323.— Anteriou Pou-
TION OP A CiuLoroD.
at = antennae.
mx^ = umxilla.
mx'^ = second maxillu.
mxp = luaxilliped.
clawlike and is perforated by the duct of a poison-glaud.
Each trunk-segment, of which there may be over a hundred]
bears but a single pair of appendages,
there being no compound segments as
in the Diplopoda. Each leg is as a
rule seven-jointed, the coxal joints of
those of the same segment being widely
separated, and there is no modifica-
tion of the seventh pair to serve as
copulatory organs., though the pair of
tlie penultimate segment are much
reduced in size and lie at the sides of
the reproductive orifice.
Stigmata are usually wanting in the
first three trunk-segments, but occur in
a certain number of the others, lying
usually laterally between the segments
except in Scutigera, in which they have a dorsal position.
They open into branched tracheal trunks which usually an-
astomose with one another, though in Scutigera they open
into sacs from which a large number of simple uubranched
tracheal tubes arise arranged in a bunch as in the Diplopoda.
Crural glands occur on the coxal joints of several of the
posterior appendages.
The nervous system is arranged as in other Myriapods, and
simple eyes are usually present, in Scutigera only being closely
aggregated together to form a faceted eye. Tliis, however, is
not a compound eye exactly similar to that of the Insects, but
is to be regarded simply as a close aggregation of simple
eyes.
The reproductive organs are usually paired, and the sexes
separate. The ducts unite before opening to the exterior, so
that there is but a single opening situated on the antepenulti-
mate segment of the trunk, the appendages of which are
j,neatly reduced in size. The embryos of Scolopendra and
GeopJiilm leave the egg with almost the same number of ap-
pendages as the adult, while those of Scutigera and Lithohius
possess but seven pairs of legs (in addition to the maxillipeds)
HUil gradually acquire others by successive moults.
486
INVERTEBRATE MORPHOLOGY.
In Scutigera, a form wLicli frequents the warmer parts of
the world, the dorsal surface of the body is covered in by
eight shieldlike fok^s which conceal a certain number of the
segments, which are about fifteen in number. Lithobius has
the same number of segments a.id is common under stones,
etc., as is also Geophilvs and Scolopendra, both elongated forms,
the former usually without eyes, while the latter usually
possesses them but has only some nine or ten pairs of stig-
mata. Some of the species of Scolopendra, especially those
living in warm countries, grow to a considerable size and are
capable of inflicting a dangerous wound.
4. Order Symphyla.
The order Symphyla contains a number of small forms
referable to one or two genera, of which the best known is the
genus ScolopendreUa (Fig. 224). Unfortunately the details of
ti'e structure of the members of the group are by no means
well known, a circumstance all the more to be regretted siuce
/ScolopendreUa seems to possess certain Insect-like features.
The body is elongated, and on the dorsal
surface possesses a number of plates
which overlap slightly, but which do
not correspond in number with the ap-
pendages. Tlie head bears a pair of
h)iig many-jointed antennre, and behind
these, in the region of the mouth, is a
pair of mandibles and a single pair of
maxilhe, both these last-named aj)-
pendages l)eing deeply imbedded as it
were in the tissues of the head, their
Fio. 224.- ScolopendreUa ^'P« ""^.V projecting. The first pair of
im7naculata (fiow lkunib). truukappeudages is not transformed into
maxillipeds as in the Chilopoda, but is
ambulatory in function, and most, but not all, of the succeed-
ing segments, of which there are apparently fourteen, bear a
pair of tive-joiuted legs terminated by two claws. Attached
to the coxal joints oi most of tiiese appendages is a peculiar
Hpurlike process, internal to whicli is situated a protrusible
TYPE Tli ACHE ATA.
487
glandular sac which is probably to be regarded as a crural
glaud. The last pair of appendages may be uiijoiuted, each
bearing a tactile seta, and attached to the last segment is a
pair of conical processes each of which has opening at its tip
the duct of a spinning-gland.
Two stigmata, situated at the base of the antennre, are the
..uly ones which occur, their position being very remarkable
Tliey open into bunches of branched trachea3 which extend
throughout the greater portion of the body, leaving only the
appendages and the posterior part of the trunk destitute of
uu air-supply. The Malpighian tubules attached to the
limd-gut are very long, and salivary glands opening upon the
lauxilliu are present.
Eyes do not occur. Both t) a male and female repro-
ductive organs are paired. There is but a single genital pore
iu either sex, situated in the mid-ventral line towards the
front of the fourth truuk-segmen', and the oviducts or vasa
(loferentia Uxiite before communicating with it. Very little is
kucwu as yet concerning the development of SaP ■^pendrella.
It Jias been considered by some to show marked affinities
with the lusecta, and the name given to the order implies the
l)f)ssibility of its being a connecting link between that group
iiud the Myriapoda. The spurlike processes have been re-
garded as limb-rudimeuts, in which case it seems possible
tliat each segment may really be a double segment and that
the Sym])hyla have close affinities with the Diplopoda.
III. Class Insecta.
The class Insecta is far riciior in species than any other
clasHof animals, some two hundred thousand s})ocies belonging
to it being known to exist, and of these about eighty thousand
are beetles. A very large number are i)rovided with organs
of flight and may be termed aiirial ; others are terrestrial,
living either upon the surface of the earth or excavating bur-
rows beneath its surface; while some have adai)ted them-
-■" -"' • .....,.- ..,..!5. .-I iii-., aaa t^ihcrs aiu even murme,
members of the genus IhthhaU'K l)eing found on the surface
of the ocean many miles from land. Many species, living as
488
IN VERTEBRA TE MORPUOLOO Y.
they do upon vej,'e table food either in the adult or larval
stages, aud occurriug occasionally iu enormous numbers, form
powerful enemies to the horticulturist and agriculturist, the
Eocky Mountain Locust, for example, devastating at times
the crops, while fruit and forest trees are injured by the at-
tacks of other forms.
The Insecta differ from other Tracheata iu having the
body divided into three well-marked regions. The most an-
terior of these is the unsegmented head, bearing the autenuio
and the masticatory appendages, and immediately following
it is the thorax, composed of three segments, the prothorax,
mesothorax, and metaihorax, each of the last two bearing
usually a pair of wings upon its dorsal surface, while pos-
teriorly is the segmented abdomen composed typically of ten
segments, sometimes as broad as the thorax at the junction
with that region, sometimes contracted to a narrow stalk. In
many cases, however, the apparent number of segments falls
below ten owing to the fusion of certain of the posterior seg-
ments or the union of the anterior segment with the thorax,
and in the Butterflies and two-winged Flies the thoracic seg-
ments seem to be reduced to two owing to the close associii-
tion of the metathorax with the first abdominal segment.
Four pairs of appendages are borne by the head. The
autenme, and indeed all the appendages, vary greatly in
shape in the various groups, but are usually long slender
raultiarticulate structures i)r()vided with sensory hairs. The
masticatvry appendages are a pair of mandibles aud two
pairs of maxilla", which are variously specialized for bitinj,',
l)iercing, or sucking. The most typical condition is that iii
which the entire apj)aratuH is adapted for biting and that niav
be described here, leaving special modifications to bo con-
sidered in connection with tlie orders in which they occnr,
The mandibles (Fig. 225, C) are strong unjointed toothed
plates which meet together in the middle line and are ))!()-
vided with strong muscles. The first maxilhe, or, as they are
usually termed, the nnixilhe (Fig. 225, li), on the other hand
are distinctly i(jinte(l, luuX cniiHiHt of u !)as•'/'>
tVf Ui t r t ; t ' • •,
•oars on its
lates in one
or two unsegmented plates of which the innermost is usually
toothed. The second maxill* (Fig. 225, A) are also jointed
and are fused together to form a lower lip, or laUum. The
fused basal joints form the
sKbmentum {sm), the second
joints the mentum (m), which
bears, as does the stipes of the
maxillcTO, a jointed pal}) (p) and
terminates frequently in two
uujointed plate-like processes.
The three pairs of appendages
of the thorax are typically
ambulatory, but are niodilied
for clasping, swimming, digging,
etc., according to the habits of
the insect. They typically con- ^.
sist of a basal joint, the coxa ^^"" 225.— Moutii-paiits op a Bkr-
•succeeded by one or two small ''"^f ^''7/'"""«««-
... ,, "^ , A = labium,
joints, the trochanter, upon B = miuilla.
which follow a femur, a tibia, C = miiudible.
and a tarsus, the last consisting
of five (occasionally four) short joints, the terminal one bear-
ii:g two claws or ungues. Abdominal appendages are ropre-
sented only by cerci, which are usually many-jointed structures
occurring near the posterior end of the body in many groups
of lusecta (Fig. 23G), and by the pairs of spurlike processes
which occur on a number of the al)dominal segments of the
Thysanura and which recall the spurs on the trunk-segments
of Scolopendrella. In the embryos of probably all forms
rudimentary appendages are found on some of the abdominal
segments, but they later disapjiear, showing, however, a de-
scent of the Insecta from forms in which abdominal a])pen-
ss-
ing poison -glands in ccninection with a complicated stinginj,'-
apjmratus, which is a modified ovipositor.
The respiratory stigmata vary greatly in number in dif-
ferent groups of Insects. In the wingless Thysanura and
Collembola there are usually ten stigmata on each side of the
groups which
Pulex, Meh.
□aites, Neuter
, when their
ictures, pro-
blood-lacuu;e
ter, however,
ity being ob-
i which they
at plates so
) wiug, which
;aut arrauge-
)ecome more
3f atklitioual
. 239) which
wings, which
3 two-winged
iich reduced,
id structures
I metathonix.
e, usually of
hairlike i)ro-
jrlands opeii-
inection with
)le glanduhir
t, on the jtb-
bola close to
those forms,
liniilar struc-
>ly represent
o be wautiii;,'
■)ssess glands
■glands occur
also possess-
,ted stingiiifj;-
miber in dif-
ysanura and
)h side of the
TYPE TRACHEATA. 49^
body, two being situated on the sides of the thorax and eight
ou the abdomen, but in Cmnpodea the number is reduced to
hree pan-s. which occur upon the thorax. In the winged
orms the number also varies somewhat, but there are agdn
typically ten pairs, arranged as in the Thysanura. They Tea
into short trunks, which, in a.mpo.te, ramify through the
body without anastomosing, but more usually they are uni ed
on each side of the body by a longitudinal 'tube, to^;! et
pass off numerous branches penetrating to all parts of the
body, and transverse connecting tubes passing between t le
systems of the two sides (see Fig. 215). In certain fonns
dn t cW "f ' '"' *'' longitudinal tubes are frequenS;
dilated to form air-sacs, as in the
Bees, or numerous air-sacs may occur
which may be more or less emptied
or expanded according to the will of
the iijsect, the specific gravitv of the
body being thus altered. 'lu the
jupiatic larvfe Avhich occur in some
forms, such as the May-fiies (Epheme-
iKhe, Fig. 220), adaptations occur for
the breathing of air dissolved in the
water, the sides of the body in the
abdominal region being prolonged into
;i number of pairs of platelike process-
es, into which branches of the trachero
project, an interchange of the gases
contained in the trachea? for those
dissolved in the water taking i)lace
through the walls of the plates, simi-
liuly to what occurs in the brauchia) ^'"- 226.-Lauva op an
of the Crustacea, though in these fornw ^''"'^^'*'"^«""'""" ''«'msj.
the exchange is directly with the gl": " = '''''''' '''''''^^
of the blood These structures are consequently termed
-heal branchuo, and while they are functional, the'stign.ata
'•' closed only opening when the adult stage is reached and a
torrestrud life adopted. As a rule the tracheal bn.,..].! te
i"own off at the m.)nlt by which the adult L,
nit m a few forms they persist throughout life
orni is reached.
1''
i
I !
492
INVERTEBRATE MORPHOLOGY.
m
\ I
A dermal muscular system does not exist, but complicated
and well-developed muscles are present for the movement of
the various parts of the body, those occurring in the thorax
bein^ especially well developed and serving for the movement
of the limbs and wings. As in other Tracheates the coeloin
is lacunar, and the heart lies in a pericardial sinus below the
dorsal surface of the bodj', alar muscles extending from it to
the walls of the body and partly dividing the sinus into a dor-
sal and a ventral chamber. In the Thysanura the heart
extends from the posterior thoracic region throughout tho
greater part of the abdomen, and consists of nine chambers
separated by valves and each provided with a pair of ostia ami
a pair of alar muscles. In the majority of forms (Fig. 227, //),
however, the heart is entirely confined to the abdominal
region, and the number of chambers, though frequently as
high as eight, may be greatly reduced. An aorta extends
forwards from the anterior chamber into the head, in the
Butterflies (Fig. 227) dilating in the thorax to form a second-
ary heart {ciK), and sends off branches which quickly empty
into the lacunar spaces.
The greater portion of the abdomen is occupied by a
peculiar tissue, termed the fat-body, in which the various
organs are more or less imbedded, and which receives its
name from the fact that its cells contain globules of fatty
matter, and in the adult insect usually also concretions of uric
acid. It is not necessarily confined to the abdomen, but may
extend into the thorax or even into the head. In certain
Beetles— the Fireflies (LampyridjB) and Pyrophorus of the
West Indies — certain regions of the body, especially the
abdomen, and, in Pyrophorus, two spots upon the thorax, give
out under certain conditions, apparently under control of the
animal, a very bright light, usually spoken of as a phosphoies-
cence. The tissue which produces the light is tlie fat-body,
or special portions of it abundantly sui)plied by trachea', ami
the process seems to be one of oxidation of phosphorus,
containing substances. The exact nature of the phenoniciiou
is but poi)rly understood at present, and it is not possible hy
any means at our disposal to produce in the laboratory a
TYPE Tit ACHE AT A.
493
light equal in iuteusity to that of the Firefly with the espenili-
tare of as little euerg3%
The digestive tract is as a rule much more complicated
than ill other classes of Tracheates aud is generally more or
less twisted or contorted in the abdominal region, so that
usually it is longer than the body. The mouth is bounded
in front by a usually large upper lip or labrum, generally
described with the mouth-parts, but distinguished from them
in not representing a pair of appendages. The anterior
portion of the intestine, the fore-gut, is ectodermal in origin
ah
as
Fig. 227.— Structure op Butterfly, Danais archippus (after Buroess).
a ■-= ttiiteuim
ag = accessory gland.
ah = accessory heart.
an = abdominal ganglion.
be = bursa copulalrix.
e — crop.
cc = canal uniting be aud oviduct.
ce = cerebral ganglion.
h = heart.
I = thoracic limbs.
mv = Malpighian tubules.
t)cl = oviduct.
ov = ovary.
ph =z pharynx.
pi = palp.
s = stomach.
sg = salivary gland.
tg = thoracic ganglion.
I-TIT = thoracic segments.
1-9 = abdominal segments.
as in other Tracheates and consists of a mouth-cavity
into which, or in its neighborhood, the ducts of one or
more generally well-developed salivary glands (Fig. 227, .vr/)
open. The secretion of these glands varies considerably in
different forms, one of the pairs present in the larva) of "the
Biitterflies and certain Moths being transformed into silk-
spinning glands, the silk of the Silkworm being a product of
their activity. When digestive the secretion seems to have
a peptonizing effect as well as the power of transforming
starch into suLmr, jiiid is consequently of fongidorable diges-
tive importance. The mouth-cavity opens behind into an
494
IN VERTEBRA TE MORPHOL OQT.
oesophagus, whose posterior region is frequently dilated iuto a
crop (Fig. 227, c) which in some Beetles is lined with chitinous
teeth or bars and whose walls are muscular, the apparatus
probably serving for a further mastication of the food. The
mid-gut which succeeds the crop is usually dilated into
a stomach (s), lined in some cases by glandular cells, or,
in others, having opening iuto it numerous glaudukr diver-
ticula, the so-called liver-pouches. The hind-gut, like the
fore-gut of ectodermal origin, has opening into its anterior
extremity the Malpighiau tubules {mv), which vary consider-
ably in number, amounting to nearly one hundred in some
Hymenopterans, though more usually limited to from four to
eight. They are excretory in function, and are apparently the
Tig. 228.— Different Akiiangements op the Nertous System in Insect j
(from Qeoenbaur). A, Termes ; B, Dytiscus ; C, a fly.
only excretory organs which occur. The anus is situated at
the extremity of the body, and in close proximity to it odor-
iferous glands frequently open into the hiud-gut, serving as
organs of defence. In some cases they secrete an acrid fluid
which, as in the Bombardier beetle {Brachimis), can be ex-
pelled with almost explosive force.
The nervous system in forms where it shows the least
amount of modification (Fig. 228, A) consists (1) of a supia-
oesophageal mass composed apparently of three pairs i)f
ganglia and supplying the eyes and the antennre ; (2) of a sul)-
CGSophageal mass composed also of three pairs of ganglia
supplying the segments indicated by the mandibles, the
TYPE TRACHEA TA.
495
ilated iuto a
th cLitinous
e apparatus
I food. The
Llilated iuto
ir cells, or,
dulcr diver-
ut, like the
its auterior
vy cousider-
'ed iu some
rom four to
pureiitlj the
EM IN Inbect:
Y-
situated at
to it odor-
serving ilS
acrid fluid
can be ex-
s the least
)f a supiii-
e jjairs of
2) of a sul)-
of ganglia
libles, the
laaxillee, and the labium ; (3) of three pairs of ganglia in the
corresponding thoracic segments ; and (4) of a chain of ab-
dominal ganglia, a pair occurring in each segment except
usually the last two or three, in which a compound ganglion
occurs. Frequently, however, this typical condition is modi-
fied by a greater or less concentration of the various ganglia,
the thoracic ganglia fusing to a single mass, as may also, more
or less perfectly, the ganglia of the abdominal chain (Fig. 228,
7>), and the latter may even unite with the thoracic ganglia to
form a single mass situated in the thorax, as in certain two-
winged flies (Fig. 228, C). A visceral system is usually pres-
ent arising from the supraoesophageal (cerebral) mass and
being distributed to the walls of the digestive tract.
The antennffi of insects seem to act as sense-organs, and
serve apparently to control the flight, since when removed the
insect is not able to fly with its accustomed ability. So too
it seems probable that in the Ants and Roaches these appen-
dages are the seat of the olfactory sense, and iu the Mosquito
it seems that certain hairs upon them may be auditory in
function. Compound eyes, frequently consisting of several
thousand omraatidia, are usually present, as well as a small
number of simple eyes (ocelli) situated upon the dorsal sur-
face of the head. Special organs, which have usually been
considered auditory, also occur in many forms, varying con-
siderably in complexity. In its simple form such an organ
vnsists of a single nerve-fibre which dilates into a ganglion-
prolonged into a terminal hair which is enclosed within
. sheath fastened at one end to the wall of the body. This
whole apparatus is termed a chordotonal organ, and T.iere is
usually attached to the sheath just where the hair arises from
the ganglion a ligament, which is also inserted iuto the body-
wall. In the majority of cases a number of ganglion-cells and
liairs are associated to form a chordotonal organ (Fig. 229)
the various hairs sometimes being grouped within a single
slieath,— sometimes, however, spreading out in a fanlike man-
lier, each possessing its own sheath. These organs occur in vari
ous parts of the body, on the antennsp or on the lim])s In
tlie grasshoppers (Acridiidre) the first abdominal segment
hears on either side a thin tense membrane, a thinned portion
496
INVERTEBRATE MORPHOLOGY.
of the cuticle, recalliug the tjmpauic membraue of the human
ear, beneath aud iu couuection with which is a chordotoual
apparatus, further improved by the occurrence in close prox-
imity to it of a saclike enlargement of a trachea which serves
as a resonator. Similar organs occur in pairs on opposite
sides of the tibiro of the first pair of legs in the Crickets
(Gryllidse), and seem from their structure to be auditory
Fig. 229.— Subgenual Chordotonal Organ of the Tibia op the Second
Thoracic Appendage of Isopteryx (after Graber from Lang).
bk = blood-corpuscles. gz = ucrvo-cells.
c = intcgmeut. tr = trachea.
es = teiralnal ligaiueut. se = teniiiual balrs and sheaths.
organs, whence the conclusion that the more simple chordo-
tonal organs also subserve this function.
It is interesting to note that the males of the forms provided -vitli a
tympanal organ possess the power of making a harsh or sharp chirpiiiir
noise, produced in the Grasshopper by rubbing the femora of the hind legs
which are furnisiied on their inner surfaces with a row of line teeth, ovor
the strong marginal veins of the anterior pair of wings ; and in the Crickets
and Locustida? by rubbing together the two anterior wings, a row of toetii
upon a vein of one wing working upon a projecting smooth vein of the
other. The male Cicadas also make a similar noise, the stridulatiiig appa-
ratus resembling that of the Grasshoppers, and in all cases it seems to be a
sexuj'l characteristic serving to attract the females.
The sexes are separate, and a more or less distinct sexual
dimorphism occurs, the males being usually smaller and more
slender than the females. In some cases, as in the TnKS(i('k-
moth (Orgyia), the female lacks wings and has a very different
TYPE TRACHEATA.
497
appearance from the males, and iu many Beetles the male is
adorned with spines and tubercles upon the head which are
but rudimentary or absent in the female. Differences in the
shape of the antenna and the presence or absence of stridu-
lating organs also serve to distinguish the two sexes iu some
of the groups. In a few forms a polymorphism is produced
by the failure of certain individuals to reach sexual maturity
and by the assumption by them of certain special structural
characteristics. Examples of such cases are afforded by the
Bees, Ants, and Termites, the workers of the first two groups
bemg immature females, while in the Termites (Fig. 237) the
so-called neuters may be either males or females, always,
however, immature.
The ovaries (Fig. 227, ov) are paired and consist of a
varying but usually rather large number of tubes, which start
from a common basis. At the extremity of each tube is the
germ-producing region, the rest of the tube beiug divided into
a series of chambers each of which contains an ovum sur-
rounded by a lajer of follicle-cells. Not unfrequently the
chambers are arranged more or less distinctly in pairs, the
lower one of each pair containing an ovum, while the upper
contains a number of small cells similar iu appearance to the
primary germ-cells, but which serve as nutrition for the ovum
which gradually absorbs them (see Fig. 20). From each
ovary an oviduct arises, the two, however, soon uniting, and
receiving, usually not far from the unpaired orifice, the ducts
of various glands {ag) whose secretion serves to cause an
adhesion of the ova to the structures on which they are
deposited. A receptaculum semiuis is usually present, and
there is frequently a large pouch, partially separated from the
oviducts, which receives the male organ during copulation and
is termed the bursa copulatru- (be). The genital orifice is situ-
ated on the ventral surface of the ninth abdominal segment
and is usually surrounded by a number of papilhe, or some-
times by long processes, which serve as ovipositors and are
to be regarded simply as processes of the segments from which
they arise and not as modified limbs.
The testes are also paired, each being composed of a.
number of separate spherical or tubular portions. The ducts.
tss
498
INVERTEBRA TE MORPHOLOO Y.
from these various portions on each side unite to form a vas
deferens which may dilate into a vesicula seminalis and then,
uniting with its fellow of the opposite side, forms the ductus
eJHCulatorius. Occasionally the vesicula is unpaired arising
from the point of union of the two vasa deferentia, and very
frequently accessory glands occur. The ductus ejaculatorius
opens usually on the ventral surface of the tenth abdominal
segment, and projections of the body-wall in the vicinity of
the orifice form a groove or tube through which the sperma-
tozoa, usually united into spermatophores, are introduced
into the bursa copulatrix of the female.
Parthenogenesis occurs as a normal process in certain
Insects, though always associated with true sexual reproduc-
FiG. 2.2Q.— Aphis mail. Winged and Wingless Forms (from Packard).
iiou. Examples of it are found in certain Coccidee {Aspidio-
tits) and in some of the Gall-wasps (Cynipidse), the fertilized
ova producing both males and females, while in the Bees, for
example, in which both fertilized and unfertilized ova are de-
posited, the latter give rise to drones or males alone, while
workers or queens, i.e. the females, develop from the fertilized
ova. Occasionally heterogony occurs, as in the Plant-lice
(Aphidaj). These forms under favorable conditions of tem-
perature and food produce viviparously usually wingless indi-
viduals, not, however, from true ova, but by a process which
may rather be compared to internal budding, as in the Rediiv
of certain Trematoda. Generation after generation of such
individuals may be produced during the summer, but on the
TYPH TU ACHE AT A.
49^
5m Packard).
approach of cold weather or ou the exhaustion of the food-
supply males and fen. ales appear by which true fertilized ova
are produced, and fr nn these, surviving the winter, viviparous
lieterogonous females develop.
In the genus Phylloxera, whicli has played such havoc ou grape-vine^
ill France, a greater complication of generations occurs. A winter egg,
which has survived beneath the bark of the vine, gives rise to wingless
forms which migrate to the roots, and there produce numerous genera-
tions. After a time winged forms appear which ascend from the roots
and, reproducing parthenogenetically, increase rapidly in number and serve
to distribute the species over wider areas. Certain of these jjroduce small
ova from which males develop, and others larger ones which give rise to
females, both sexes being destitute of both wings and digestive tract, and
by these forms the fertilized winter eggs are produced.
In certain flies {3Iiastor, Cecidomyia) psedogenesis occurs»
the female reproductive organs becoming mature while the
iusect is still in the larval stage, and the ova, developing par-
thenogenetically within the body, give rise to another gen-
eration of larvsB. This process may be repeated several
times, the last generation of larva) developing into the adult
form (see Fig. 29).
The more primitive Insects, the Thysanura and Collem-
bola, leave the egg in a form resembling the adult, differing
from it only in size and in the immaturity of the reproduc-
tive organs, and i)ass through no marked metamorphosis
during their post-embryonic development. Such forms are
termed ametaholic. A similar absence of metamorphosis i^
found in certain forms degenerated by parasitism and lacking
Avings, but these have evidently descended from winged forms
which passed through a certain amcmt of metamorphism»
so that the ametabolism is secondary and should be distin-
guished from the primitive ametabolism of the Thysanura.
In the majority of winged forms, however, a more or less
pronounced metamorphosis occurs. In the simpler cases the
young are distinguishable from the adults by the absence or
but slight development of the wings, which become larger
after successive moults, the adult form being thus gradually
acquired. In tliese cases of gradual metamorphosis the
habit ' of the adult and larva are similar, but where they
S3
500
INVERTEBRATE MORPHOLOGY.
differ greater cliauges result, leading to hemimetahoUsm. This;
occurs, for iustauce, iu the Fish-flies (Ephenieridse) aud
Dragou-llies {Lihelhda), in which the larva) are adapted for au
aquatic life and possess tracheal brauchiie (Ephemeridse) aud
other features which are lost, either gradually by successive
moults or suddenly at the last moult, the adult winged Dragon-
fly, for instance, issuing from a peculiar aquatic larva with
the merest rudiments ol wings.
Finally, a large number of forms are hohmetaholic. In
such cases the habits of the larva3 are different from those of
the adults; for instance, the larvje of the Butterflies, Wu^
caterpillars (Fig. 231), are wornilike creatures with power-
mpmmmmm
Fio. 231.— Lauva, ri:i>A, and l.MAfio uv I'lcris oleracea (ivom Riley),
ful jaws feeding ou plant-tissues, while in the adults the mouth-
parts are adapted for sucking. The transformation from the
larva to the adult is accomplished by the intervention of a
resting stage or pupa, dur-ng which no uutiition is taken, ami
when the transformation takes place the fully.deveh)}i('(l
insect or imago issues from the ru])tured skin of the ))ii)ia.
The pupa varies considerably in form in different grou]).s,
in some being enclosed in a silken case manufactured by
the larva before the last moult and termed a cocoon. In
some cases the adult apjiendages project from the bpdy of
the pupa (pupa JiberaX but iu other cases they are united
with the surface of the body and but indistinctly visible
{pupa ohtecta), au arrangement usually found in the Buttor-
flies, whose pnpjo, owing to their frequent brilliant coIoim-
tion, are termed chrysaluh. a term which lias been somewhat
incorrectly extended to the mummy-like puptr of other forms.
TYPE TRACHEA TA.
501
liually, m some of the two-winged ilies the pupa is euclosed
Mithiu the Lxst larval skin, possessing then a cvliudiical form
without any indication of the adult Umbs (pupa cocwctata).
A metamorphosis in ^vhich a distinct pupa-stage occurs is said
to be "complete" in contradistinction to the hemimetabolic
form frequently spoken of as "incomi)lete."
Mention sliould bo made here of the dimorpliisu, or polymorphism whidi
o.:ct.rs m certai.. adult Insects. It has already received' passing n.e.itiun
M>. 497), but in addition to the frequently-occurriuf,' sexual dimorphism
there occurs in forms which live together in colonies a i)olvmorphism asso-
ciated with a division of labor on the parts of the members of the colony
liius m the Bees there are found the drones or males with heavy bodies
Ih.'queen or female, as large as the drones but with a much more fjlonder
body, and the workers, which are sterile females (listingiiish,.d bv their
smaller size and by other features, such as a peculiar moditication'of the
lilMas of the last pair of legs which a.lapt them for the collection of pollen
Ironi the (lowers which they visit. Among the Ants a similar trim..rpl,ism
orcurs, males, females, and neuters or workers constituting the colony and
iM some f epical forms the workers are of two kinds, namely, ordinary
workers wh 1 small heads and mandibles, and soldiers with large heads anil
strong prominent mandibles, whose functions are indicated by the popular
name applied to them, though guards would perhaps be nrnre" appropriate
luially, among the Termites, popularly known as the White Ants four
lorins. I.e., males, females, workers, and .soldiers, al.so occur.
In certain Buttertiies a peculiar form of dimorphism ..r trimorphi.sm
termed "seasonal dimorphism" occurs, an excellent exami)le of it bein-
<'thT..d by the American Popff'o AJax, of .vhieh there have been described
(luve distinct varieties, diflVriiig markedly in e.,l..rati..n both in the males
aiul (ho females, and distinguished as the yarielies W„fs/u,\ Tvhmouhhs
iiiu\ Marce/lus'. From ehry.salids which have pas,sed the winter then. i,ateh
out in the early days of spring forms belonging to the variety ]Va/sf,;i mu\
somewhat lat('r, from tlx.se whose d.-n-lopment lias been reiarded' the
Ti/amonide,s f(nms. Drring the early i art of summer th,. WaMuf f,",rms
(ii.'out and a little later the Telamnnhhs also disappear, both forms pre-
vioiisly, however, .lepositing ova, ino.st of which develop into larvie and
Wuvsahdsand hatch out in the later moi.lhs (.f summer as the J/r,,w//?/.»
fonu. whose ova, again developing int., ciiry.salids. pass the wiui,-r in (hat
M;ii>'. and give rise in the following spring successively to the Wal.shii and
hhnnonides forms. The three varieties are evidently prcMluced by influ-
<'n'( .s a..(iug upon (he ehry.salis and differing nceording to the sea.son. por-
liiips iieeording to temperature, whence the distiniruisl
mis lorm of dimorplii.er, being usually ten, thougli in
Canipodta they are reduced to three, and the trachew in this
TYPE TR ACHE ATA.
503
same form are interesting in being destitute of longitiuliual
ami transverse anastomoses.
Lepismai. frequently found in houses, in attics and similar
places, feeding upon woollen, linen, and other fabrics, but also
on meal or sugar. Campodea (Fig. 232). on the other hand, is
o be found under stones or dried leaves and is a small white
torm, by no means uncommon.
2. Order Collembola.
_ The Collembola are distinguished from the Thysanura by
the abdomen consisting usually of but six segments, and in
some cases the number is even smaller. The body in Podura
IS covered with scales, and the terminal segment of the body
IS usually provided with two processes which may be bent up
underneath the abdomen and then suddenly extended, pro^
pelling the lusect to a considerable distance. These structures
are absent in the adult Anurida, but occur in young spec"
n.ens and their occurrence and function have suggested the
]H>lHilar name of Spring-tails applied to the order Neither
Hbdomiual appendages nor coxal glands occur, but the first
segment bears a peculiar organ, having in Anurida the form
ol a saccular protrusion, which is probably adhesive in func
.on The antenna are usually short, and bear in some fonns
a.i antennal sense-organ similar to that of Carnpnt compound eyes never occur. A peculiar oilman! ying 1 "^
In.ul the bases of the antenna, and hence termed tL pl
4. Order Odonata.
The members of this order, the Dragon-flies, are elongated
forms with two pairs of nearly equal, abundantly-veined winj,'s
of usually large size, all the forms being excellent fliers and
seeking their prey in the air. The head is united to the
thorax by a narrow stalk which permits extensive rotation of
the head, and the abdomen, terminating in two unsegmeuted
platelike cerci, is long, and in the large Dragon-flies, jEsvhim
and Diplax (Fig. 235), and in the brightly-colored Agrio7i very
slender, though somewhat stouter in the genus LihelMa. Tlie
anteuntB are very small and the mouth-parts adapted for bitiiip,
while the legs are slender, the anterior pair being directed
somewhat forwards so as to serve for grasping the prey.
The lateral compound eyes are very large, meeting on the
dorsum of the head, and
in front of them are situ-
ated a pair of small ocelli.
The larv8B are aquiitic
and are characterized by
the remarkable develoj)-
ment of the labium, wliicli
is very much enlarged,
terminating iu two power-
Fia. i'in.— Diplax elisa (from Packahd). £jj| j^^yj^ j^^j provided witli
a hiugo, 30 tliat it can be flexed so as to lie beneath the In:! !
or suddenly thrust out to capture the unwary prey. This
TYPE TB A CHE ATA.
507
apparatus is termed the "mask." Respiration is carried on
by tracheal gills, consisting in Agrion of three leaflike pro
cesses situated at the posterior end of the body, and also by
the terminal portion of the intestine, into .vhich Avater is
taken and which is abundantly supplied with tracheae The
water can be forcibly expelled from the intestine, serving to
l.ropel the insect through the water if it so desires. The
metamorphosis is incomplete.
5. Order Plecoptera.
The Plecoptera, or Stone-flies (Fig. 236), are found in the
viciniiy of water and have a somewhat elongated body fre-
quently terminating in two long
cerci {Perla). The antennse are long
and filiform and the mouth-parts
adapted for biting, while the legs
are strong aud used for walking.
Two pairs of wings occur almost
e.iual in size, but lacking the com-
.ucated venation found in the Odo-
liatu, aud when at rest lie fiat upon Fig. 236. -Stone fly, Perla.
tiie abdomen, completely concealing it. The larva) are
a(iiiatic, and are usually to be found in considerable numbers
u.i.ler stones in swiftly-runiiing streams. Tliey recall the
ili.ysanura in their appearance, and possess tracheal branchhB
ou the under surface of the thorax, which in some forms are
retained m the adult. The metamorphosis is gradual or in-
oomplete according as these structures are or are not retained
m tlie imago.
G. Order Corrodentia.
The mmnbers of this group possess biting mouth-parts
and are su.netimes destitute of wings. The Termites, or
A\ lute Ants, live in colonies aud show a ,,olym„rphisin. TJie
males aud feuiales, termed kings and queens (Fj.. 237 I ]})
a.v at first provided with largo wings resembliug those of the
i !o<^optera, but after the maniage flight settle to the .n-ouinl
and become wingless. The workers select from the many pairs
I
608
INVERTEBRATE MORPHOLOGY.
one for each nest, the remaining uuselected ones soon dyin.). The Aphid» also posses
a a rule upon the antepenultimate abdom/nal segment pair
of tubular elevations or papilte from which a sweet secreUon
«..nes the so-called "Honey-aew," which covers he Wes
ami stems of the plants npon which the Insects live ZZ
-gerly sought for by various Insects, more especL™ by
The larv* of the Ehynchota as a rule resemble the aduU,
even to the .tructure of the ..outh-parts, anrthe metam^r
P .OS. .s consequently gradual. 'bI Ckada forms, I o leve "
mf..ce of the ground and living „,,„„ the roots of tree,
I becomes ransformed into a pupa, which, however con
t»-es to lead an active existence, becoming quieslen '
lort time before tlie moult which
only
results in the formation of
512
INVERTEBRATE MORPHOLOGY.
I! : M
the imago, very different iu appearance from the pupa. The
metamorphosis here approaches the complete type.
9. Order Coleoptera.
The order Coleoptera includes the Beetles and is richer
in s]iecies than any other order of animals. The members of
the oup are characterized by the anterior wings bein^ coii-
vertetl into hard chitiuous plates, the elytra, which cover iu
and protect the posterior membranous wings and the abdo-
den, being short only in a few forms, such as the Buryiujr.
beetles {Necrophorus), in which the tip of the abdomen remaiiTs
exposed, and the Staphylinidae, or liove-beetles, and /deloc, in
which they cover only the more anterior portions of the ab-
domen, the posterior wings in the last-named form beiu^r
wanting, as they may also be iu some of the Weevils. Occa"
sionally, as in the Fireflies {Lampt/rls), the elytra are but
slightly thickened, and in some forms they may be completely
fused together.
The autenn.ne vary greatly iu shape, being usually filiform
and sometimes very long, as in the Boring-beetles {Monohum.
Fig. %'i^. — Cotalpa lanigera and its Lauva {a) (from Packard).
mils, Olytus, Saperda, etc.), though occasionally, as iu tlie
Lamellicorn beetles {JIelolonfha~the June Bugs and CotaJpa,
Fig. 239), the termiual joints are flattened aud folded together
like the leaves of a book. The mouth-parts (Fig. 225) are in
all cases adapted for biting, and the legs for locomoticm. Iu
the Lady-bugs {Coccinella) the tarsus consists of but lour
joints, one of which is rudimentary, while in the Weevils
(Curculiouida3), in wdiich the anterior part of the head is pro-
TYPE TIUCHEATA.
S18
lougecl into a cyl.mliical s„o„tIike process at the extremity
otwnchis l.e fflo„th,iuthe Bori„g.beetle«, and iu tl.e Po
Uto-beet e (Doryphra) it is forme.l of five joints, one of ^,^t
» exceed.n,l3. .s.uall. In otl.er forms, such as Mdoc and the
-hster-beetles (Z,«„), the tarsi of the two anterior pairs of
leKs are five.j„,nted and those of tl,e last pair fonr-L ted
and n others again, snch as tl,e Fireflies, the Cliclc-beefe
(tlaternla,) the Lamellicornes, the Bnrjing-beetles ml'
he Ca,ab d,e (U.dosoma, Cnmhus. l[arp_du., /ijhinns, etc
and the I,ger.beetles (CkhuMa). all the tarsi are Hve-io n ted
and all the j.nnts approximately equally developed.
Iu the'l TJT '""'' r"'^' '" '""" '" "'^ "^'ff"-™' genera.
lu the L„d. bugs audson.e other forms they are Thysanuri-
..■u, the three anterior trunk-segu.ents (corresponding to he
hie the abdomen terminates in a pair of cerci. In some
,,ter-beetles ((?,„„„) tracheal gills are present, and Z
la V e ot the Lamelhcorns (Fig. 23U. „) are soft-bodied eyele ;
wh.te h,rms, characterized by a saclike dilatation of tlie lasl
abdommal se,.nent, and live beneath the surface of t e
K oum feeding up.n the roots of grasses. In the Click-bet
t e., (E laternte the body of the larva is elongated and slen-
.k- and very hard, these forms being kno™ as the wire-
>1 plants In the Bormg.beetles, the larvre, which excavate
"..rows beneath the bark or in the wood ^f various ee,
ave he l.mbs almost or quite rudimentary, while maggot.'
like larvffi are characteristic of the Weevils
The larva, whose life nnay be prolonged through several
■ears, passes finally into a resting p„ pa stage of*lhe'Z
onn,resembhngin the body form and%he mouth-part the
.HI. l.o,.oy, .he parasite shp, „,«>„ L eg«, wlnl'Mrcoll."": 1!^
614
INVERTEBRATE MORPHOLOOT.
transforms into a maggotlike second larva which lives upon the honey on
the surface of which it floats, and after a time passes into a resting pseudo-
chrysalis stage, from which a larva similar to tlie second one emerges, and
this finally transforms into a pupa which gives rise to the adult.
m
10. Order Neuroptera.
The Neurojjtera are characterized by the abundant and
rich venation of their wings, in which numerous cross-veins
extend between the longitudinal ones. The mouth-parl.i are
adapted for biting, the mandibles being in some forms {Cory,
dalis) very large. The lace-winged flies {Chrysopa) also be-
long to this group, as does also the Ant-lion {Ifyrmeleon, Fi".
240), whose larva excavates a funnel in loose sand, and
buries itself at the bottom with only the head and powerful
Fig. 2i0. —Myn)>eleon obsoletus (from Packard).
mandibles projecting, ready to snap up any insect which s]ii)s
down the yielding sides of the trap. The larvM> are usnullv
Thysanuriform, those of Chri/sopa attacking Aphides, whence
they are frequently termed Apliis-lions, while tliose oi Ci>nj.
dalis are acpiatic and possess tracheal branchiae upon tlu'
abdomen. This larva is familiar to anglers as the Holl-
gramite. The metamorphosis is complete.
11. Order Panorpata.
This order contains a small number of forms, the majority
of which possess membranous wings reseml)ling tlios(> ol' tlic
Neuroptera, except that the cross-veins are not so numoruiis.
The anterior part of the head is produced into a downwaidlv
projecting snout, at the extremity of whicli are the smail
biting mouth-parts, the arrangement recalling tliat foum! in
the Curculioniihe among the Coleoptera. In the genus l' the corre-
,' insects, ox-
ler teriniuiil
re united to
I the higher
i), however,
m) are quite
um is nnu'li
ts pulps (//))
id well (Ic-
ube is coiii-
!ed into two
nd by their
I, the hirvii'
irs. Thi'ir
TYPE TR ACHE ATA. 5^7
of the Cabbage; many other similar examples might be
given A few of the Microlepidoptera possess aquatic'lal^
).utthey orm exceptions. In the typical cateiillar the^
are, in addition to the three pairs of thoracic legs, Le pa s of
•short stout prop-legs situated upon the third, fourt lifi th
s.xth, and tenth abdominal segments, and the body may be
covered with hairs of various lengths, as in the larvafof nnn'
-oths (e.g. the Woolly Bear, Spilosonu,), or may possZ
spiny processes, as in the larvae of the Mourning-cloak Butter
% {Vanessa) which feeds on the Willow, ''or v.dou l"
shaped tubercles, as in the American silkworm iTelea).^
e ^o.op.a arva. In one group of moths, the Geome tril
bu two or three pairs of prop-legs occur, situated on tlfe
oe postei-ior segments, and in progression these for
ai uv these legs up close to the thoracic limbs, throwing tl e
intervening portion of the body into a loop, whlnce the ten s
measuring-worms" or "loopers" often applied to 1.17
rare cases, as in a few Microlepidopteri, the lai s
iviHiout feet ami luaKKotlike. ""v.iis
The i,„p,. „,. ohi-ysulis is of the ohMa variety, au.l i, f™
n bythe larva whose salivary glau.ls are couverte iu to
>! mm„K-«lau,ls. A ceoou is „„,re Renerallv present i/tl
Moths than ,n the B„ttorllies, whose chrysali.fs Lre snspen.ed
.V a patch of silk to which the hin.l en,l of the p„ a is I
tadiecl or may be in acljition slnn.- in ., sille,, 1 „ ■
ro..n,l the body near the nml.lle (Kg. Lii) ""'"''
14. Order Kymenoptera.
The Hymenoptera possess fonr membranous wings with
"mparatn-ely few veins and not covered with scah-s ^r ,m
. pos enor. The al d.m.en is sometimes l,roa,Ily attached
lo thorax as „, the Saw-flies (Tenthredinida,),bnt r"
- ally the anterior one (Bees) or two (Ants) abdo ninal s el .
N..;..t» are very narrow, so tl„>t the al„lon,en Meen.s to CL
-..".'" by a stalk. The fenndes possess ovipositors which
-,■ be retractile and provide.l with a poison^iand, fo™,- '!
518
INVERTEBRATE MORPHOLOGY.
If 1
mjcp
efficient organs of offence and defence, as in tlie Ants, Bees,
and Wasps, or else long and slender and but partially retrac-
tile and destitute of a poison-gland, as in the Saw-flies, Gull-
flies, and IchueumonidsB.
The mouth-parts are adapted partly for biting and partly
for licking. The mandibles (Fig. 242,
mn) are well developed and fitted for
biting in all forms, and in the Teu-
thredinidse the maxilloe are also like
those of biting insects, while the
inner of the two terminal plates of
the labium are united to form a tube,
the outer plates remaining separate.
In the Bees and Wasps the maxilhe
{inx) become elongated and are uo
longer adapted for biting, and the
inner terminal plates of the labium
are fused together to form a luiij;
touguelike structure, the glossa [I),
the outer plates forming what are
termed the paraglossae ( pg). The
entire apparatus is adapted for biting
aud also for licking up the huiiej
contained in the nectaries of flowers.
The great majority of forms are
solitary, but a few Bees {^pis, Bom-
hits) and Was])S {Vespa, Sphex) and the Ants [Formioi,
Camponohis) form social aggregations with more or less
pronounced polymor})hism, to which reference has already
been made. The Gall-flies {Cynips) lay their eggs upon the
leaves or stems of plants, at the same time injecting a jxiisou
which causes a proliferation of the plant-tissues, forming' ;i
gall in the interior of which is the larva of the insect ; while
many forms, such as the Ichneumon-flies, Proctotrupes, Ptero-
malm, Microgtister, etc., are parasi<^ic in their larval stago, the
eggs being deposited in or xipon the bodies of the larNicnf
other insects, a very decided cluv'k being exerted U])oii tin'
larvio of injuriouH insects, such as the Cabbage-butterfly, h.v
these forms.
Pig. 243. — MouTH-rAUTB of
Bee, Anthophora (after
Newport rroin Gbggnbaur).
I — glossii.
Ip = labial palp.
mn = mandible.
mx = maxilla.
mxp = maxillary palp.
pg = paruglossa.
TYPE TRACHEATA.
619
lie Ants, Bees,
irtially retrac-
^aw-flies, Gull-
The lar™ of the Tenthredinida,, for example that of the
Poar.sl„g (&fa»J«,), „hi„h feeds upon the leaves of the pear
ue resemble the caterpillars iu possessing prop-wf o
forms, however, owing to parasitise, or to being in contec
Pig. 343.-, which ar„ those of the mesothorar, the
620
INVERTEBRATE MORPHOLOGY.
metathoracic pair being usually represented by a pair of club-
shaped bodies on the sides of the segment, termed hcdteres or
balancers. The wings are always trans-
parent and the veins by no means
abundant. In a few forms, such as the
Sheep-tick (Melophagus) and the Flejis
{Ihdex), the wings are entirely wanting,'
in harmony with the parasitic habits
which these forms possess, but they
form exceptions to the general rule.
The mouth-parts are adapted for
sucking and also for piercing; the
labruxn (Fig. 245, Ir) and labium {la)
are prolonged into grooved processes,
forming together a tube within which
lie, in the female Mosquitoes (Oulex)
and Gadflies (Tabanus), two pairs of
elongated needlelike rods which repre-
sent the mandibles (md) and maxillio
(mx), to which a lifth unpaired stylet
may be added which arises as a growth
from the lower wall of the pharynx
{hy). In other forms the maxillae only
OF A Gnat, Culex, the ^^^.ve the ucicular form, the mandibles
Labrum turned to fusing with the labrum, and in all cases
ONE SIDE (fro,u h.ht- the maxillary palps are present, whil,>
the labial palps are undeveloped, lu
the ordinary House-fly (Mtisca) the ex-
tremity of the sucking-tube is expanded
into a disklike structure, and in all
forms the salivary glands open near the
extremity of the tube,
usually niaggotlike (Fig. 244), entirely
destitute of feet, and in some forms the head even is indis-
tinguishable. The metamorphosis is complete, the pupa boiiig
in the Mosquitoes active, swimming about in water, thou^^h
more usually it is incapable of motion, and enclosed witliiu
the last larval skin, thus belonging to the coarctata variety.
Fig. 245.— Mouth-parts
WIG)
hy = hypopharyux, a
process of labium.
I'i = liibiuin.
Ir = labium.
md — mandible.
7IU --= maxilla).
p — maxilliiry palp.
The larva) are
TYPE TR ACHE AT A.
031
^^^^iopment and Affinities of the Imeofn Th. i .
dovelopment cannot be discussed 11. ^^^y stages of Insect
books of Embryology, but ^2' ^Id Se 7n '"'"l^ *^ *^^^-
uoinenou which occurs duriue the IZf 1 ^ *" remarkable phe-
nnaginal conditions in tl^Xm '^7'" """^ '''' ^""^^^ '^ ^he
describing the developme t o ^ A^^^^^^^^^^^ " ""''''" '"
the transition from one sta^eto hVn / . ^""'"^"'^ ''"* ^^^'-^^ ^"^''^g
e-tion of certain parL ^^^^21:^^2 7\ ^"'"^""^ '■^^'^"-
tl.o same process occurs durinr he Z ^ ^" ^^'f ^'o'^metabolic Insects
t'.o majority of the muscle ad' t e S^difl "\'""^ '^^P^^^'™'^'
«...,, so that ti,e idem t'v of tl. v '''' '°' ''^'°"•^^-
scrved throughout the process. The im 1 fal d ^'^"°'^\«''g^n« ^^ Pro-
portions of the original anla-^en o? Zl '''' '^ ^' '^^^^^ed as
rained during larvanifeir.!:r:b;onL"Sn"^^^^^ ""^' '''"^ '^■
be N^t :tt :r;^r :rrc:^^.:^^^^ r-r- ^^ '--
eates a descent from Apterygote ance or !nd ^^"^""5 "^'"^ '''"'* ■"^"-
larva. of a wormlike ot maLtUke form r T ''"^''' ''^'''^' P''^^*^-^'
highly specialized. It is Tn thes.^^^^ I" ''" probability the most
occurs, and it is selJl::drnt t r^- d .?:n:r^'''^^^ ?^^^""^^^
i;l.o.ses are more primitive than the nf, i^ '^^ uITT'I "^''^'"«^-
•icponds upon the differences in habit and stn ctu tf the b '"''''^''^'^^'^^
and becomes more and more conn.tpt. o„ '.''^"'^ "^ ^he larva and imago,
•Icpart more and u^oreZL^r^l^^^^^^ V '''''' "'^^ ''"'^«'"««
Consequently it may be cone udnh^tnorf""'™ ''^' '' ^^^^^^ure.
which retain most perfectly Zh 1^1. "I' "'' '^'' "^°«^ ^''^^'^^^
elnu-acters. These L ^l^" ^^XiX^"^'' ^"^ "'^'"'^""''''^
both in the adult and larval stages' t. Cor d^iiarT''^
not become modified by parasitism) a 1 tlw n h / ^' '" ^^'^ ^'^'^
•'^^f,-,d it is intorestL^otri;^st.^ cZZu?" ''T'' '-
•-r g^^;';;j-~- - - -r r ^-- -
...o^rr :;S:rtJ-rtS --;;;:- r-s in the .rv.
f"">'naptera, is that of the Thysa.m terfwh i '"'" ''^"'" ^^^ *''«
'""i"Hte affinities with the R Stf t L 7 ' ' "°^ °^«»th-parts
'^ --d group t^ceable back tr^ ^im^ P^^^: '''''''' ^-"^"«
;je resemblances l^i.^ll^Za':^:::;:^^-:'^ T""''''^
^^- character of the wings and by the mouth^arts."";:: .l!: I^;^' ;^
622
INVERTEBRATE MORPHOLOGY.
^\
lated are the Neuroptera with Thysanuriform larvae, probably to be re-
garded as a group which has undergone a development parallel to that of
the Ephemeridae and Odonata, the relationship bei.ig traceable back to an
ancestor common to it and the Ephemeridae. To this group may also bo
referred the Plecoptera.
A fourth group includes those forms in which the larvfB are provided
with prop-logs, secondary forms in which all indications of the Thysanurid
ancestors have disappeared. Of such forms the Panorpata show relation-
ships on the one hand with the Ephemerid group, and somewhat closely
related are the Trichoptera, whose entire organization points to a close
affinity with the Microlepidoptera. From the primitive Microlepidoijter-i
two lines of descent are probably to be traced, one leading to the Maero'-
lepidoptera and the other to the primitive Hyraenoptera, the resemblance
between the larvae and the mouth-parts of the Tenthredinid*, and these
of the Microlepidoptera being very striking.
The two remaining orders, the Coleoptera and Diptera, are very hi-rhiy
specialized, both being holometabolic, and the temptation is to look" for
their ancestors in forms with a similar metamorphosis. This tempfuiou
may be justified in the case of the Diptera, whose larva are the most
modified of all, and it is not impossible that they hnve descended from
primitive Hymenopteran ancestors, their nearest existing relatives beiii-
the Tenthredinidae, whose sluglike larvae, suggest not a little the k-i.s't
modihed Dipteran maggots. With the Coleoptera, however, the case'is
different, and it seems more probable that their holometabolisin has l.,.,-n
acquired quite independently of that of the other holometabolic orders
The larvae of some beetles, notably those of the Coocinellid*, are markclly
Thysanuriform, and prop-legs do not occur in the order. To which of the
groups they are to be referred it is very difficult to say, though the mouth
parts and the arrangement and structure of the wings in the adults point
to an affinity witli the Orthoptera.
Granting a descent of the Pterygota from wingless ancestors, it boco.nos
an interesting problem to discover the origin of the wings. Attempts have
been made to show that they are modified tracheal branchias a theory
which necessitates tiie derivation of the Pterygota from aquatic ancestors
bucli a derivation, however, is unsupported by any evidence at pivsnK af
our disposal, it being much more probable that the immediate ancestors of
the Pterygota wore terrestrial, just as Campodea is to-day. The wiix's
arise in the emt^ryo as dorsal outpouchings of the meso- and metathora'x,
traeliea3 later pushing out into them, and transient indicaiions of o„t-
pouchings of the prothorax also occur in some embryos. It has been s,,,.-
gcsted that primarily the wings were platelike outgrowths of the thoracic
seginents which served to break the fall and increased the distance irav-
ers.'d by jumping Insects, and in support of this view tiie fact n.av he
mentioned that many Apterygota are saltatorial. The limitation ..f' ihc
wings to the meso- and metuthorax may stand in some rnlutinn („ the
centre of gravity of the body.
TYPE THACIIEATA. ^^3
The Phylogeny of the Trachentn if t. u
together the Crustacea, Araor^r:^^ ^X ^ •''' ^"^^''^ *« "-*«
Arthropoaa^ characterized by iX^^.^^'^T ^l^ ''''^'' ^^'«"P' ^^e
-ourrence of jointed limbs, and by Te Ts ,1 '"""' '""''•^' ^^ "'«
i"nb,s; and furthermore it ms been cuVZ "'^ ^'^^"' ^*^'"S °'«d'fied
-"1 the Tracheata as closely related '"fr^^^/^ ««"«ider the Arachnida
..oup. of trachea. The eiriy ^oc ^ oT'^^^^^^
groups also show many points of sinXTtvH 'fP™'"* in the three
«i.ows decided differences in the deTa Is h1^^-^ ^ ''''''' examinaUoa
'"ay have operated to produce the Z?.i.- ''' ^""^^'•gent evolution
-'i it can be settled only by a onsZit '';',;'' P^*^'^^"^ *° ^« ^^^tled"
winch indicate the phyloger.; of t' e v '" "'" '"^^« ^^ «"^ <^i«Posa
wouM prove entirei;be'yofd[h:'limL^^^^^r^ ^^^^
to ^^St r r ^ - "tirfP^^ - - Crustacea is
descended trom ^-..P^^ll Ice a^^^^^^^^^^^^ '^-e in all probability
;n the,r affinities. Are the Tracheair then « T'-^^^^t^'^'y Crustacean
aeea and from forms which poLesl tel^V O^ ''' '"" ''' ^--
of the group negatives any such sunnnJn t "^ P'"^^^'^* knowledge
Tracheata should, like the^p.^er^rv de^^^^^
ancestors ; it must rather be conceded that h • f'"^ ^'-^i'^-^.-like
and the Arachnida are due to conterln?" *'^^^''°•'^^'ties between them
ant.es to the acquisition of comraSv I^ "' *'" ^'"^'•^'^"'« «•'«'•
he ova, distributed in a similar mannri'T """T' ^' '"^^'y^'^ ^«
to the exigencies of a terrestrial TiJe 11^0 '""''^""^^ of the adult
groups seems at first an importan noinlof T"'' ^^ ''''^''^ *" both
only by a community of descent butl ""^^""'^ *^ '^« «««o»»ted for
terrestrial Isopoda trache^ So ocL 'i^ u" br " r?''^"'^ ^^^' - ^^e
their occurrence in these forms ranireW. ,""' "P'^^*^"'^' ^"^ that
anyphylogenetic significance, i ievidenf hTf."^ "'''^P^""°"' ^'thout
catjons of affinity is much reduc d It 'I J T "^^P^-^^nce as indi-
Malpighiantubulesof theArachnidaandcrul ' P''"*'^^ '^"^ ^''^^ ^he
-e X.eheata they are eetoder^rS:^— ^1:;:^—
- Ariidl;^"^^^ . closely related to
«o that the conclusion seems inevitable '1?"^^'''^'' f ''''' P'-^no^nced,
nvo,l from Annelid-forms and hav. h f Tracheata have been de
{-dent of that of the J^^^^ ^^^ ^^ P"^'«^-y P-tically indt
Id ancestors of Peripatus and those of If.; n V'"''^' '^''' ^^^ ^"ne-
«losely related, and that certain of 1 p''»«tacea were more or less
^-'Ps are thus to be acco'^^/fL t^S" ^'T'*"'"^« ^^ ^» '^^ *h-
P'-e^-'nt ,„ a position to judge One'r o n T''^* '^*^"* ^'« ^^^ "ot at
pound eyes of similar stn.cf. re ^l^l^r '' "'^ "««"--ce of com-
tion, sine« it --^ « ■ " groups, seems w^-thv -f -- -^
624
INVERTEBRA TE MOBPHOLOQ T.
\\t
markable instance of convergent evolution. It is to be noticed that tlm
most primitive Insects, the forms througn which affinities +o the Crustiicoa
if they exist must be traced, are as a rule provided only with simple eyes,
a condition repeated in the eyes of Insect larvae — a fact which indicates tluit
the compound eyes are structures which were not characteristic of tlie
primitive Insects, but have developed within the limits of the group aiid
can therefore have no phyletic connection with the compound eyes of the
Crustacea. Adding to this fact the independently-developed tendency to
form compound eyes seen in certain Annelida and Pelecypod Mollusks, it
seems probable that notwithstanding their remarkable structural siinilaii-
ties the compound eyes of Crustacea and Insects have been independently
acquired. Instead, therefore, of uniting the three groups together as a typo
Arthroprda equivalent to the other types, it seems preferable to separate
them as distinct, just as is done with the Annelida and Mollusca, and the
Annelida and Prosopygia.
Starting, then, with the supposition that PeripaUis has descended from
Annelid ancestors and represents the ancestors of the Myriapoda, the rela-
tionships of the various orders of this class and of the Insects remains to
be traced. Unfortunately a large gap exists between Peripatus and any
recent Myriapods, and it is possible that this class is a heterogeneous group ;
indeed oy some recent authors it has been sugj^ested that it should be
done away with as a class, the Chilopods being united with the Insecta to
form one class, while the Diplopods (perhaps witl; the Pauropoda associated
with them) should form a second. There is no doubt but that Peripatus
possesses many tracheate peculiarities, but its affinities to the remaining
Tracheates are much more remote than those which exist between the vari-
ous groups of Myriapoda, or between any of the.w groups and the Insecta.
The character of the various appendages considered in relation with the
nervous system seems to afford an admirable means of indica' "ng the rela-
tionships of the various groups. The brain of Peripatus seems to be
formed by the fusion of three pairs of ganglia ; the most anterior and dor-
sal of these gives rise to the antennal nerve and the most posterior inner-
vates the mandibles, while upon the middle one, which is closely related to
the mandibular ganglion, the eye seems to be placed. It may be assumed
that the ganglia with which the e}-es are associated represent the Annelid
supraffisophageal or cerebral ganglia and may therefore be termed the jiro-
tocerebrura, while the antennary ganglia form the deu.,ocerebrum, and tlie
mandibular the tritocerebrum. In the Myriapods and Insects the brain is
also composed of three parts to which the same names are applied, tlio
antennae being innervated from the deutocerebrum, while the tritocerebrum
lacks a corresponding appendage, though in certain Insects transient indi-
cations of a tritocerebral appendage have been seen. Bearing these facts
in mind, the ganglia and appendages of the various groups may thus be
tabulated, and to make the comparison complete the Crustacea are also in-
cluded.
f
TYPE TRACHEATA.
526
Ganglion.
Crustacea.
Peripatus.
Diplopoda.
Chilopoda.
Inseet/i.
Deutocare-
hral.
Tritiicere-
bral.
Ist postoral
•Jd "
3.1
nh "
.5th "
6th "
Antennules
Antennae
Mandibles
Ist maxillae
ad
Ist thoracic limb
ad "
Antennae ?
Mandibles
Oral papillae
1st legs
2d '•
3d "
4th "
6th "
Antennae
Antennae
Antennae
Mandibles
Maxillae
Ist legs
ad "
3d "
4th "
Mandibles
Is maxillae
2d
Maxillipedes
1st legs
3d "
Mandibles
1st maxillae
ad "
1st legs
2d "
8d "
;ea are also in-
It will be seen from this that in the Diplopoda the arrangement is
intermediate between that found in Peripatus md that of ihe Chilopoda
while these latter approach closely the Insecta, and this seems to be the ac-
tual relationship, Scolopendrella forming an intermediate link between the
Chilopods and the Insecta, approaching the Thysanura closely in the ar-
rangement of the mouth-parts and in the number of segments of which the
body is composed. The Diplopoda, it is true, pass through a larval stage in
which but SIX legs are present, and it might at first sight be supposed that
this indicates an affinity with the Insecta, but these legs do not belong to
the .same segments as do those of the Insects, and furthermore the occur-
rence of rudimentary abdominal appendages in some Thysanura, as well as
111 the embryonic stages of probably all Pterygota, indicates that the In-
secta have been derived immediately from forms with many pairs of appen-
dages, and these forms seem to be represented most accurately by the exist-
ing Scolopendrella.
SUBKINGDOM METAZOA.
TYPE TRACHEATA.
I. Class Protracheata. -Annelid-like forms ; trunk not differentiated
into thorax and abdomen ; w ith nephridia. Peripatus
II. Class Myriapoda. -Elongated forms; trunk not differentiated into
thorjix and abdomen ; posterior trunk-segments with appen-
dages in the adult.
1. Order Pauropoda. -^m^W forms ; with only one pair of maxillje •
antenn* ending in three flagella ; reproductive orifices at basi,s
of third pair of trunk-appemlag.'s. Pauropus, Eurypauropns
2. Order Diplopoda.-Wnh only one pair of maxill* : antennae
simple ; reproductive orifice on .second or ),etweeu second and
third truiik-segmonts ; mo.st of the trunk-.segments with two
pairs of legs. luhm, Lysiopetalum, Polydesmus, Strow/vlo-
soma, Glomeris.
3. Order Chil»poda.-W ith two pairsof maxilla; and with maxillipeds-
antenn* simple; reproductive orifice on the antepenultimate
segment: each tr!,!,k-sec.n3ent with a single pair of legs.
Qeqphilus, Scolopendra, LitUobiun, JScutigera.
11
526
IN VEKTEBUA TE MORPHOLOQ T.
m
4. Order Symphyla. —Vfith only one pair of maxillEo and no maxilli-
peds ; antenme simple ; most of the trunk-segments with u
single pair of legs. Scolopendrella.
III. Class Insecta. — Trunk differentiated into thorax coniposea of throe
rings and an abdomen with typically ten segments.
1. SubcUiss Apterygota.—T\\ov&.x without wings; abdominal segments
sometimes with rudimentary limbs in the adult.
1. Order Thysanura. — Abdomen with ten segments, bearing two or
three cerci ; abdominal appendages frequently present. Le-
pisma, Campodea.
2. Order Collembola. — Abdomen with six segments terminating in
two springing-orgaus ; abdominal appendages wanting. Fodura,
Anurida.
2. Subclass Pterygota. — "With usually two pairs of wings situated on
the meso- and nietathoracic segments ; abdominal appendages
wanting in adults.
1. Order Dermaptera.—KhAomQn. with forceplike cerci ; anterior
wings small and chitinous, posterior folded like a fan and also
transversely; mouth-parts biting; metamorphosis gradual.
Forjicula, Labia.
2. Order Orthoptera. — Abdomen usually with cerci ; anterior wings
chitinous, covering the posterior, which fold fanlike and some-
times also transversely ; mouth-parts biting ; metamorphosis
gradual. Caloptenus, Gryllus, Qryllotalpa, Periplaneta, Dia-
pheromera.
3. Order Ephemeridce. — Abdomen with two long cerci ; wings mem-
branous and richly veined, the anterior larger ; not folded when
at rest ; mouth-parts biting, but reduced ; metamorphosis in-
complete. Ephemera.
4. Order Odonata. — Abdomen with two platelike cerci ; wings mem-
branous and richly veined, not folded when at rest ; month-
parts biting; metamorphosis incomplete, sometimes approaching
completeness. Libellula, jEschna, Agrion, Diplax.
5. Order Pteo/>^era.— Abdomen usually with cerci; wings membra-
nous, moderately veined with few cross-veins ; the anterior cov-
ering the posterior when at rest ; mouth-parts biting ; meta-
morphosis incomplete. Perla.
6. Order Corrodentia. —Abdomen without cerci ; wings sometimes
wanting (parasites and neuters), membranous, the anterior cov-
ering the posterior when at rest ; mouth-parts biting ; meta-
morphosis incomplete or wanting. Termes (with polymorphism),
Atropos, Liotheum, Trichndectes.
7. Order Thysanoptera. — Abdomen without cerci ; wings sometimes
wanting, narrow, poorly veined, fringed with hairs ; the anterior
pair covering the posterior when at rest ; mouth-parts piercing
and sucking; metamorphosis incomplete. Thrips, Phl(Xothrips.
linal segments
present. Le-
«.
TYPE TliACHEATA. 537
Order Rhpnchota.-Ahdom.n without cerci ; basal portion of
anterior wings chitinous. posterior wings and tips of anterior
membranous, or else both membranous, the anterior the larger
or both wanting ; mouth-parts piercing and sucking ; meta.nor-
phosis incomplete.
Anterior wings chitinous at base (Henuptera). Anasa, Notonecta,
Belostoma, Ranatra, Hydrometra, Halobates, Cimex, PediouUs
(wings wanting in the last two)
"^"Jrr'n "f ; ^"''' "^^^^--^^^^^ iHomoptera). Cicada, Aspidi.
in^letsf S:r '^^'"''"'"■' ^"'"' ^^'"^^ "^'^ '^ ^^"""^
Order 6>.^.o^^.m. -Abdomen without cerci ; anterior wings chi-
tinous, covering in the posterior when at rest ; mouth-parts
biting ; metamorphosis complete. "''" paus
(a) Tarsi of four joints, one of them ver> small (Cryptote.
tramera). Coccinella.
(b) Tarsi of five joints, one of which is very small (Cn/ptopen-
tainera). Ourculionidae, Clytm, Saperda, Monohammus,
Boryphora. '
(c) Tarsi of posterior legs four-jointed, of two anterior pairs
tive-jomted {Heteromera). Meloe, Lytta.
(^Tar.si all five-jointed and all the joints of equal size
{Pentamera). Lampyris, Elateridfe, Melolontha, Necro-
phorus, Staphylinidae, Hydrophilus, Qyrinus, Bra-
ofmms, Harpalus, Carahus, Calosoma, Ckindela.
OvA^Neuroptera.-AMom^n without cerci ; wings membranous
richly veined with numerous cross-veins ; mouth-parts bidng •
11. Order Panorpato.-Abdomen sometimes with cerci ; wings mem-
branous with few cross-veins; mouth-parts biting, af end of
cylindrical rostrum ; metamorphosis complete. Panorpa.
Order r..c/.op<.,.a._Abdomen without cerci ; wings covered with
hairs or scales, posterior ones larger and folded fanlike wlieu
at rest ; mouth-parts sucking ; metamorphosis comi)lete Phnj.
ganea, Anaholia. "
Order Lepidoptera.-Ahdomen without cerci ; wings covered with
seaK not folded when at rest, though they may overlap; mol h-
parts usually sucking ; metamorphosis complet^
Small forms (Microlepidoptera). Tinea, Carpocapsa, Pyralid*
Oigyia, Telea, Pierts, Vanessa, Papilio
nous, without scales, not folded ; mouth-parts biting and lap-
ping ; metamorphosis complete.
Ovipositor rfitrnnti!f> with n'^i"'iri f-! of North
America. Proc. and Bulletin U. S. Nat. Museum
A. S. Packard^ Monograph of the Geomeirid Moths. Report U. S. Geolodcal
Survey of the Territories. X, 1876. ^. o «eoiogicai
E. T. Cre..on. Synopsi.. of the Families and Genera of the Hymenoptera of
A^nencanorih of Mexico together mth a Catalogue of DescnLl SpZa^d
hibhography. Trans American Entomolo^rical S(»ciety. 1887
H Loew and Baron Osten Sacken. Monograph of the Diptera of North America
bnulh,sonian Institution. Miscellaneous Collection, v,, 18C3 • vi 1864
viii, 1869; XI, 1873. «'"« , vi. 1004 ,
8. H. Scudder. The Fossil Insects of North America. New York 1890
J. H^ aiul A. B. Com.tock. A Manual for the Study of Insects, iihaca! N. Y.
See also the publications of the U. 8. Entomological Commission and the
o> o. V. KUey, A. 8. Packard, and others,
STKrcTl'HAL.
H. Orenaolier Untersuch-mgen iiher das Sehorgan der Arthropoden. Omiin-
E Burge.. Contributions to the Anatomy of the MUkweid liutterfl., (Danai,
"'-^y. Anniversary Memoirs B<..ton Soc. Nat. History, 1880.
18m ^'^'"'^ ««'* 0/ tf>e Garden of the Gods, etc. Philndelphla,
V. Qrab«r. We chonhUmal Sinnesorgane und das GehOrder Insekten. Archiv
[ti'" niikroHk. Anat., xx. 18H'.J. ■'»-<»-utv
^ "i^'^SSa. ^"^ ^"""^^ '^'' ^^''^"- Arbeiteu a. d. zool. Inst. Wien,
jJO
Sir John Lubbock.
INVERTEBRA TE MORPHOLOO T.
The Oi'igin and Metamorphosis of Insects. London, 1883.
Ants, Bees, and Wasps. London and New York, 1883.
J. A. Palmen. Zur vergleicJienden Anatomie der Ausfurhrungsgiinge der Sex-
ualorgane beiden Insekten. Morpholog. Jahrbuch, ix, 1883.
J.Carriere. Die Sehorgane der Thiere vergleicJiendanatomisch dargestelU.
MUnchen, 1885.
B. Orassi. Anatomia comparata dei Tiaanuri e considerazioni generali tulV
organizzazione degli Inaeiti. Atti della R. Accad. Lincei, Berie lY. it,
1887.
X. Heider. Die embryonale EiUwicklung von Hydrophiln piceus L. Jena,
1889.
J. Van Rees. Beitrdge zur Kenntniss der inneren Metamorplioae von Mu&ca
vomitoria. Zoolog. JabrbUcher, iii, 1888.
V. Oraber. Vergleicliende Studien am Keimstreif der Insekten. Denkaclir.
Acad. Wisseusch. Wien, lviii, 1890.
H. T. Fernald. The Relationships of Arthropods. Studies from the Biolog,
Labor. Johns Hopkins Univ., iv, 1890.
B. T. lowno. Anatomy, Physiology, Morpliology, and Development of the Blow-
fly. London, 1890-91.
W. M. Wheeler. A Co7itribution to Insect Embryology. Journ. of Morphology,
VIII, 1893.
T. H. Huxley. Anatomy of Cockroach. Text-book of Anatomy of Invertebrate
Animals. New York, 1878.
W. K. Brooke. Anatomy of Oratahopper. Hand-book of Invertebrate Zoology.
Boston, 1890.
'X.
TYPE ECHINODERMA.
631
sA dargeatelU.
CHAPTER XVI.
TYPE ECHINODERMA.
The Echinoderms are exclusively marine organisms and
vary considerably in shape, some forms being elongated and
vermiform, others stellate, and others again almost spherical.
Whatever may be the shape, however, a well-marked radial
symmetry can be distinguished, which suggested to the older
zoologists the association of the members of this group with
the Ccelentera in a type Radiata. The radii in the Echino-
darma are, however, almost invariably five, instead of four or
six or some multiple of these numbers as in the Ccelentera ;
and, furthermore, while in the Ccelentera the radial symmetry
represents a primitive condition and any departure from it
towards bilaterality, as in the Anthozoa, is secondary, the
reverse is the case witii the Echinoderma. The larval forms
of this group are strictly bilateral, and even in the adults
certain organs or parts of organs interfere with the regularity
of the pentamerous arrangement and bring about a more or
less pronounced bilaterality.
This may be clearly seen if one of the stellate forms, such
for instance as the ordinary five-rayed Starfish (Fig. 240^,
be examined. This animal consists of a central disk, at the
centre of one surface of which, the oral surface, the mouth is
found, while the anus occupies a somewhat excentric position
on the other surface, which may be termed the aboral or
ai)ical surface. From the edge of the disk the five arms or
rays project outwards, and ahmg the median line of the oral
surface of each arm there extend outwards from rings around
tlio mouth a nerve-cord and a hydroc(el canal, this latter
forming a part of a peculiar system of vessels characteristic
"• =•-.• t.i,-. ixi ^.„^-^.j^jj^,jjj.g .J. j^^-.j_ ruaiation of
these structures out along the arms, and the arrangement of
532
INVERTEBRATE MORPHOLOGY.
the other organs for the most part in conformity with the
radiation, the arms may be regarded as representing the
radial axes of the body, the interradial axes lying in the in-
tervals between them. If now the aboral surface of the disk
be examined, there will be found upon it, in one of the inter-
radii, a peculiar tubercle, known as the madreporiform tuber-
FiG. 'iiQ.—Asterias arenicola (after Aoassiz from Vebrill).
cle, which serves to place the hydrocoel system of canals in
comnuinicati< u with the exterior water. There is but ono
such tubercle, and but one canal leading down from it to tlio
hydrocrel ring which surrounds the mouth, and consequently
there can be but one plane in wliich the anini;il can be di-
vided into two siniihir i)artH. Therefore the Starfish, thou;^di
superficially appearing to j)()ssess a radial symmetry, is funda-
mentally bilateral— a statement which applies etpially well to
any member of the Echiuoderm type.
It does not necessarily follow, however, that the ])lHiie
which passes through the madreporiform tubercle is tin*
luediau plane of the body. The larvo) of the Echinodcniis
are strictly bilateral organisms, no sign of radiality beinj,'
found in thftm in an early stage of development, and it would
seem more satisfactory to take as tlie median j)lane of the
TYPE BCUINODBBMA. 533
adult animal one which ccresponds as closely as possible
-th the larval median plane. The madreporiform tubercle
...•rather the pore which corresponds to it ancrthet,
winch leads from it to the rudiment of the iyd oLl '''t
can readily be made out in the larva, of most forms and
can be seen that it lies to the left of the median p aTe "r he
l>«ly. Indeed in the larva, of some Starfishes two no e
"ccur at an early stage of development, one to the left and
the other to the nght of the median plane, the latter subse
. nently disappearing. The madreporifor,; tnbercle mi .ht"
therefore be regarded as lying to the left „f the median ,Ze
However it is impossible to tell how much modiHctio.,
has taken place during the transition from the bZ. ra to
l.e radial condition and it is not impossible that the g eat r
portion of the adult represents one of the halves tf uL
embryo, the other half remaining more or less „n evelper
Furtherniore a secondary bilaterality supervenes in ceiLt
S tl f .^'"""f," .™'' H"l"".-"'oidea which does no a ^ e
with that indicated in the precedinc imra.rra,,!, ., , . "'™
indeed the same in the two groups. n'::r;;i .;;;:";
able to assume a perfectly arbitrary method of in, Lit uj
he radii of the body, calling that radius whicl, lie, on t
e madreporiform tubercle A, that which lies to th ' l',^
.s when the animal is held with the oral surface p war K
''wlir' Z^' f- ''•/'.'"'"™'*'' "-"'-tion of the h 1?
.. atch. The interradii may be in.licated by combininir the
■Iters of adjacent radii, the interradiu, beLeen i n.l «
l'"MJg denoted by vl «. "veeu .1 ami H
The bo,Iy-wall in the Echinoderma is covered on the out
..le by a usually delicate, and in .some cases cille e"
enn which ,„ay, however, be indistinguishable fr, n ^ ,
■■ nt inesodennal tissue, in certain parts of t le b, v"
l-l.-w this ectoderm, when present, comes a layer oi me .
maal connective tissue consisting of relatively few Tel
"iil edded m a more or less Hbrillar matrix, and in tlds co ,
"ective tissue there are imb„d,l„,l „„.„„,...,... 1., '"", ".""-
". ^..me forms, such as the Ho.oThuri'an;; ^L^'XT t^^^^
634
INVERTEBRA TE MORPHOLOO T.
separated from one another so that the body-wall has a more
or less leathery consistency, but more frequently placed
almost or quite in contact with each other, and uniting in
most of the Echinoids or Sea-urchins to form a firm test en-
closing the principal vegetative organs, a small area or peri-
stome around the mouth alone remaining but partially calci-
fied and retaining a leathery consistenc}'. Spinous elevations
are frequently developed upon these dermal plates (whence
the name of the type) and may assume various forms, being
in some cases quite loug, movably articulated with the plates,
and supplied with muscles so that they may aid in locomo-
tion.
The arrangement of the calcareous plates diflfers greatly
in the different classes which com-
pose the type, but certain of them,
distinguishable by their position
and relative arrangement, reappear
in the majority of the classes.
These plates are situated at the oral
and aboral surfaces of the body.
The oral plates are not so constant
nor so numerous as the aboral or
apical, and show a tendency, even in
those groups in which they are most
highly developed, to undergo a
greater or less amount of resorption
during development, being frequent-
ly more pronounced in larval than
in adult life. Typically the oral
system consists of a central oral
plate, the orocentral, unknown in
recent forms, but occurring in cer-
tain fossil genera, and this is snr-
rounded by a riog of five plates,
which may bo termed the oral plates,
and which nave an interradial [)osi-
tion. Tin ujiical system has as a
central pli* ■ the so-called ceiifro-
dorsfd (Fig. 247, CD), which in some i-tmg is re])laced by a
Fig. 247.— Disk and Akm of
Zoroaxter, s-iiowino the
Apical System of Platks
(after Si.adkn).
an = umis.
cd = ceutio-ilorsal.
7Tit = madieporite.
T = tertliinal plate.
2 = u.'ider-basals.
8 = basal':.
4 = radials.
n^-Jf^^^^
TYPE ECIIINODEIiMA.
535
unmber of small plates between which the anal openiug of
the digestive tract is to be found. Formin- a ring around
this are frequently live plates possessing a radial position
which are termed the nnder-basah (Fig. 2^7, 2) ancl are un-
represented in certain forms ; next to these comes a secoud
circle of five plates, the bamls (Fig. 247, 3), which are inter-
radial and correspond to the oral plates, while next to these
again is a third cycle, also of five plates, the rndials (Fig 247
4), whose name denotes their position. Numerous ''other
plates may intervene in the various groups between the radials
and the orals, but their number and arrangement is not suiH-
ciently constant to permit of homologies ; the oral and apical
systems are, however, represented more or less perfectly in
all but one of the classes, and consequently deserve special
mention.
A well-developed dermal muscular system occurs in the
Holothurians in which the calcareous plates are scattered
aa.l the body-wall consequently capable of considerable con-
traction and expansion, but in other forms it is very much
reduced. In those forms in which the calcareous plates are
simply in apposition strands of muscular tissue pass from
plate to plate, a considerable amount of movement being pos-
sible, but in the Sea-urchins, for example, the dermal muscu-
lature IS almost wanting, being reduced to bands passing to
the bases of the movable sp,ines and to the complicated mas-
ticatory apparatus.
The C(Klom is somewhat complicated in its relations, which
vary considerably in the ditierent groui)s. In all enterocctaic
and schizoc(Blic portions are distinguishable, the former in
the embryo arising as pouchlike diverticula from the primi-
tive intestine or enteron, and later becoming completely con-
stricted off from it. Mucii variation occurs in the later his-
tory of the pouches in the various groups, but in general it
•nay be stated that one of them, the left, has a portion con-
stricted off from it, which forms the adult water va.<^cuhir s-ys-
>''i>i or hfilrocopi, a structure characteristic of the Echinoderms •
iiu.l furthermore this same left enterocoel communicates with'
'li(> exterior by a dorsal jiore, situated in the interradius CD
ni.l represented in the adult by one or many pores opening
536
INVERTEBRA TE MORPIIOLOO Y.
upou a sievelike calcareous plate known as the mmhrporifonii
tubercle or madreporite. The hydroccel in the adult commniii-
cates with the left enterocoel by a tube, termed the stone-
canal from the deposition of calcareous matter which occa-
sionally takes place in its walls, and so indirectly opens to
the exterior through the madreporiforni t\ibercle (see l\.
265). The various departures from this arrangement which
occur will be more conveniently considered in connection
with the special descriptions of the various groups ; the con-
dition just mentioned may be provisionally acce])tecl as rep-
resenting the typical arrangement.
After the separation of the hydroccel from the left entero-
coel, the latter and the enterocoel of the right side increase in
size and finally apply themselves closely to the inner surface
of the bodj^-wall and to the outer surface of the digestive
tract, forming the peritoneal lining of these structures. Wlieie
the two ccelomic sacs meet there are formed, of course, two
partitions extending from the body-Avall to the intestine, ami
suspending that structure between them. These partitions
are the mesenteries, but before the embryo reaches the
adult stage one of these mesenteries disappears, the oilier
persisting in a more or less perfect form. The coiling of the
intestine, which occurs frequently in the adult forms, brinjiis
about complications of the course of the >aesentery, coui))!!-
cations further increased in most cases by the formation of
other partitions which may traverse a greater oi less portion
of the coelom either longitudinally or transversely. One of
the transverse partitio" ■', most frequently present, separates
off more or less completely from the rest of the coelom, a por-
tion of it surrounding the pharyngeal region of the digestive
tract and hence termed the peripharyngeal cavity, while iu
gome cases a perianal cavity may similarly bo formed.
The hydrocoel, whose origin has been described, develojw
into a tubular ring (Fig. 248, cc) surrounding the oesophagus
quite close to the mouth. Upon this ring iu the interradii
one or several saclike diverticula, termed Polian vesicks (/)),
occur, and in one interradius a canal, the stoue-canal (sr),
passes aborally to open into a thin- walled sac termeh
In connection with the stone-canal a peculiar body is
developed r\ most forms. It? function is a matter of ques-
tion, it hnviug been at one time taken for the heart and at
another for a gland. It is generally termed the ovoid gland
(Fig. 265, og) and consists of a mass oi cells, derived from the
peritoneal lining of the enterocoel, grouped together to form
a more or less solid mass. The oral end ci the gh^nd is pro-
longed into a cordlils biructure which seems to enter into
close relationships with the oral lacunar ring (see below), while
at the other it is continued out to enter into close relationships
with the reproductive organs in a manner that will be de-
scribed when treating of those organs. Surrounding the
gland is a sinus — the axial sinus (Fig. 265, as) — sejjarated off
from the enteroccel and, in some forms, in communication
with the ampulla of the stone-canal, and the portion of the
gland which passes off towards the reproductive gland is also
surrounded by a sinus, or rather lies in the wall of a sinus
which may or may not communicate with the axial sinus but
has, like it, origin from the general enterocoel.
"What has been termed a blood system is usually present,
consisting of a tubular ring surrounding the cesophagus, and
lying between the hydrocoel-ring and the nerve-ring. Five
branches may extend oft' from it along the radii, preserving
the same relatio]is to adjacent structures as does the ring.
These spaces seem to be schizocoelic in their character, and
may be termed the schizocoelir ring and radial schizocoelic sinuses
in order to avoid confusion with another system of vessels
which sometimes lie within the sinuses and have also been
termed blood-vessels. This latter system may be termed the
lacunar system, and is composed of a network of vessels lying
in the walls of the intestine, and collecting usually into a
perioesophageal ring or plexus (Fig. 265, Ir), with which also
the ovoid gland comes into connection. In the Echinoids,
as has just been indicated, prolongations of this perioesophageal
ring or ])lexus extend out in the radial schizocoelic sinuses.
The fluids contained in the sinuses, lacuuio, hydrocrel, and
enterocoel are all very similar, consisting of a plasma contain-
ing amoeboid cells sometimes deeply pigmented. In a few
forms hsemoglobin is present ; in the Ophiuran Ophiactis it is
II
TYPE ECIIINODEBMA. 539
contamed iu flat nou-uucleatecl disks, resemWiug Mammaliau
red blood-corpuscles, floatiug iu the plasma "f 11""™*""
™seula.- system ; m the Holothuriaus, Thyo,^ aud CucJ^T,
>l .s howevev coutaiued iu au^boid corpuscles, ^hicTa e
..ost ab„u,laut m the ccelomic fluid, though occur iug dso L
tlie water vascular tubes. ^
The digestive tract is generally more or less twiste,! iuto a
:i!ht T IT' "' '" r'"^ Holothuriaus, it appea to
b .straight, ,t m to be regarded as a much-drawu-oit spiral
.nee he mesentery still retains a spiral arrangement. I '
Ho othunaus, Eclnuoids, and Starfishes it opens on the abo d
™ ace of the body, but in the Crinoids it is bent upcn itse
hat he anus ,s on the oral surface. In some Itarfls .e
tr ,ctu,'.e ^"'"rr "° ™"' '•" l^'-''^»'- ^'""O"'' accessory
t.uctu,es masticatory apparatus, ccecal pouches, etc are
Sjuitnirtr ''""'""'' "-'" "-*'- -/^«
The nervous system may be regarded as being composed of
meut as the water vascular tubes, consisting of a circumoral
or a pencesophageal ring from which fivA ,.^,i;,l "™"'°""
offiFiiT 9fi^ «,. 1 . """'"""""' nveiiidial nerves pass
>« (lig. 26o. vr and ,■»). In the Starfishes and Crinoids the
»tne system is imbedded in the ectoderm, but in other for '
.inks within the body-cavity. From it branches pa s n
ulsat the mouth to supply the walls of the oesophagus ami
ft. branches form a network covering the surface " te
W>, supplying the sense-organs which m.ay occur thereo ,
Uu. radial nerves, in addition to sending branches to joi. tl e
p derma plexus, supply the ambulacral system. Th » po
of th, nervous system may be termed the epideral
1". .on, and the second, inasmuch as it supplies the m i,, ritv
:.;: "'ti-':;"' f --3-. ■"■^3- be ter^iirthe^r::;;
wiuoi is, but when present accompanies in gener.al the eni
:^'s:r;:tf::t'''^fz.rr:t--:^;;"'^'
- '.<• entirely wanting in the Holothurians, b!it w,:eV:!r::
'> if-
640
TN VERTEBRA TE MOliPUOLOG Y.
cousists of a xm^ situated at the aboral surface of the boilj',
sending off branches to tlie reproductive organs as well as, in
some cases at least, forming anastomoses with the epidermal
83'stem.
Sense-organs of various kinds are developed. Tactile
tentacles occur at the extremities of the radii of some forms
and round the mouth in others, while in the softer-skinncnl
Holothurians tactile papilhe may occur. Eyes occur at the
extremities of the radial nerves of the Starfishes, and have
also been described as occurring in some Echinoids, while
otocysts occur in some Holothurians, sometimes in considera-
ble niimbers.
No special excretory organs occur in the Echinodermuta,
the am(i'boid cells of the cadomic fluids perhaps serving iu
some cases to remove the Avaste substances. They have beeu
observed to pass through the bodj'-wall, in regions where it is
thin, to the exterior and there degenerate. For the nujst
part, however, the waste products are deposited in the tissues,
or else pass to the exterior by osmosis. In the Holothuriaus
special branched appendages of the terminal jjortion of the
intestine apj^ear to take some part in excretion, but suck
organs do not occur in other groups.
The Echinoderms are almost invariably bisexual, and the
reproductive organs are usually situated in the interradii.
They are enclosed in a special coelomic sinus, the genital .sinus,
in whose wall may be found the branches of the aboral nerves.
From each organ or mass of reproductive cells a cellular ccud,
the genital racMs, surrounded by the sinus may be traced,
except in the Holothurians, to the ovoid gland, and it a))pears
probable that iu some cases at least the reproductive cells
originate in a part of the ovoid gland and migrate to the
reproductive organ along the rachis, becoming mature in tlieir
final position. The openings by Avhich the reproductive ele-
ments pass to the exterior vary both in number and position
in the different groups, but are usually situated on the aboral
surface of the body.
TYPE ECIIINODEltMA.
fi41
I. Class Crinoidea.
The Crinouls, or Sea-lilies (Fi<,^ 249), coustitute a group of
forms whicli lii the earlier geological i)erioas reached a hi-h
orade of developmeut, but to-day the class is represented by
eumparatively few forms, for the most part couHued to deep
Fig. 24!d.—Pentiicvinus madenranus (after Wyville Thompson from Hertwig)
water. One of the most characteristic features of the group
IS the presence of n more or less elongated cylindrical stalk
one end of which is attached to stones or other objects which
snrve as supports for the animal, while at the other end is
the body proper, which has a more or less cuplike form. In
the peculiar genus Ilolopus the stalk is thick and short, and
may be described rather as the prolonged apex of the body
642
mVEUTEDUATE MORPHOLOGY.
U
4
than as a ilistiuct stalk, while in other forms, such as Antedon
and Actinometm, the stalk, though present in young forms, is
entirely wanting in adult life, during which the animal is free-
swimming, though having the power of anchoring its.'lf
temporarily to solid objects by means of a number of slender
processes termed cirri which project from the apex of the cud
(Fig. 251, c). ^
The lower portion of the cup, or calyx, is formed by a num.
ber of series of calcareous plates united to each other l)v
sutures, while its mouth is covered in by a flat or dome-
sliaped disk in which calcareous plates may or may not lie
present. In the centre of the disk is the mouth of tlie animal,
while to one side is tlie anus, lying in the int^rradius ClK
From the mouth Ave grooves, known as the anibulucral (jrooves,
extend outwards towards the margin of the cup, and, near the
margin, brjinch, being tiien continued outwards on the f)ial
surfaces of ten arms which arise from the junction of the disk
and calyx, frequently branching in tlioir course, and bearii]v he second: and furthermore in the same forms the
b sals have also been pushed, as it were, within the calvx
lave fused to iorm a single plate, the so-called .o.sW/.
MI g. 251, 7?o,v). winch rests upon the centrod<.rsal. par-
uly dosing a cavity in that plate. The terminal ra.lials
sually present two articuL-tting facets in their distal sur-
t.U'es and are generally know., as the r,.r;7AnvV.v (Fi. 2r,0 a)
-cc he arms articulate with them. In the ^.n^TljJ:
... betw^^n each pair of first radials an interradial plate
-n s. a condition frecpiently found in fossil genera ii), but
sua^y wanting in recent forms. These various plates which
<;;•. t.tute the apical system are united by sutures, the edce«
^. .lie various senes of plates coming into contact, s.. that a
*H'"Hupportisationlod for the arms
BnoNN),
a - Hxillary plates.
* ~ ))!isa! plates.
i = iiilenadial plates.
r = radial plates.
544
INVERTEBRATE MORPHOLOGY.
These are iu reality continuations of the radial series of
plates ; iu fact, iu some forms certain of the radials appear to
enter into the formation of the arm. Iu most forms, however,
a series of arm-plates arises from each facet of the live axillar}-
plates, so that the arms are ten iu number — a condition which
finds an exception in the remarkable genus Thaiimatocrinns^
which possesses but five. In some forms these ten arms
branch dichotomously ; the plates intervening between tlio
axillaries and the first branchiug are termed brachials, those
between the first and second branchings distichals, and those
between the second aud third branchings palmars — terms
which are useful in systematic de ^criptious. These various
plates are united together b}' ligaments and muscles, or else
by ligaments alone (this last form of union being known as a
syzj/(jy), the movements of the arms noted above being thus
rendered possible. The pinnules repeat the arm iu tlieir
structure, though usually on a much-reduced scale. They
are situ ited on the joints separatiug consecutive plates of tlie
arms, aud are j)laced alternately on the right and left sides
of the arm which bears then). They appear at first to have
been produced by lateral budding from the joints, but closer
examination indicates that in reality they represent a braiidi-
iug, one of the brauches remaining small, while the other in-
creases in size and ])laces itself in the direction of the axis of
the arm. The whole arrange nnuit is comparable to that form
of inriorescence termed by botanists a scorpioid cynu^ tlie
pinnules re]>resenting the riower-])edicels. Owing to the
])inuules being iu reality one of the branches of a dich(;tt)my,
it is evident why, in those forms iu which the arms braucli,
there is uo pinnule at the joiut where the brauching ot-curs;
iu addition, however, pinnules are also lacking on sy/ygi.il
joints, so that their r^igular succession )uay be somewhat dis-
turbed.
As regards the (U-al systmn of plates an nro-ccnfral is found
in souu' fossil forms, but is unrepresented in recent gouerii.
A circle of five interradial oral plates is found iu Jlolnpns,
/thiziates
are developed, and from which strands, frequentlv with cal
careous spicules imbedded in them, usually travers; the body-"
cavity- Ihe ligaments which unite the plates of the arms
and stern are formed of this connective tissue, and contractile
hbres of a peculiar character are sparingly developed in it
stretching across the non-syzygial joints of the arms, pinnules'
and cirri, and probably also reaching a slight developmen;
111 the stem. ^
The internal structure of the Crinoids is known i^rinci-
pally from observations on Antedon, and the following account
represents what occurs in that form. The ccelom, as alreadv
stated, is t.-aversed by numerous strands of connective tissue
ami primarily consists of two cavities separated from each
other by a mesentery, each cavity being continued out into
he arms, forming the oral and alu.ral canals of these struc
ures, at the extremities of which they unite. The mesentery
does not however, long persist in its entiretv, but the two
cavities fuse, new n.embranes, h.nvever, arising and ,livi,lin-
then, m some species of Antod,n,. One of these mend.ranes
(Ug.2;>l, y.s.) Mil-rounds the intestine and forms the visceral
sac Its presence rendcM'ing the evisceration of Aiitrdon an
I'asiy.accomplished proc-ess and one which is n.ade use of
•y the annual in unfavorable conditions, a new visceral mass
-.ng later regenerated. The portion of the ccelom which
li.'H peripherally to this sac is termed the circumvisceral
l""-tion (r.), and that within it the intervisceral He), the latter
containing an axial cavity (J..) enclosed by a membrane sim.
p. VI HC-
rul Hut= and continuous with the oral co>i
I
cavities {oc) of the arms, tiie aboral
omic
cavities ((/(•) coiumuuicat-
046
INVERTEBRATE MORPHOLOGY.
iug with the circumvisceral coelora. A portiou of one of the
coelomic cavities at au earl_y stage becomes cut off from the
rest of the coelom aud divided iuto five chambers whose walls
are formed of a deuse fibrous membraue. This constitutes
•\s
Fig. 251.— Veuticai. Section rnRoroii Antedon (combination of flgures liy
l,ri)w:i; ami MAi'snALi.t.
cc — ahoml caiml nl' ann.
an — aboral iutvc.
Aj! — nxial sinus.
Br = hr.Mi'hiiil jjliitcs.
C = cirri.
cc = circuiiiviscoml ciivity.
CD = ccntiodorsal plute.
CO — central oryaii.
Do — ilori-al tirgmi.
gr — geiiiliil nichls.
/= intcHliuc.
id =: intcrvlsceral cavity.
M — uioulii.
oc = oral cavity of arm.
on = oral nervf-riuj.^.
R — radial piatts.
rh — radial lacunar vessel.
rn — radial epithelial nerve.
VOB — rosette plate.
r?o = radial hydrocojl-caual.
«c = stone-caual.
T — oral tentacle.
vs — visceral septum,
wp — vvaler-pore.
the chambered organ (ro). whicli in Antalun. lies in a cnviiy
in tlie centrodorsal pltite and is roofed over by the rosette-
phite, l)ut in other forms simply rests upon the centrodorsal;
communioating with it is the lower end of a somewhat citih-
suaped structun* termed the ihprmil 'Wfjun [Do), wliicli \no-
jects orally i)arallel to the axial co'lomic ctivity.
The e|>itlieliuni of the aborid codouiic cavities of the atiiis
is ditferentijited hero tind there into peculiar organs the ciii-
TYPE ECIIINODERMA.
547
1 of flKiires by
uted cups, consistiu^^ of slight tlepressic.ns lined by columnar
cells eacli of wiii.h bears a long ciUunu These cups are
especially abundant in the pinnules, and serve to create a
circulation of the crelomic Huid, which, as in other Echino-
(lerms, contains numerous amueboid cells lioatiug freely in it
The water vascular system, or hydroccjel, consists of a riuL^
surrounding the mouth, and sendi.ig outwards five radial
canals {rw) which lie below the ambulacral grooves and are
continued along the arms and pinnules. Occasionallv sub-
ambulacral calcareous plates are developed in the connective
tissue bel(,w the radial canals, and in some fossil forms these
plates assume a regular arrangement in two rows. At regu
lai- lutervals along the arms are situated the ambulacral ten-
tacles, which are fingerlike outpouchings of the radial canals
. estitu e of terminal > -ckers and are arranged in groups of
three, the canals being somewhat enlarged in .he region where
they occur, an indication perhaps of the ampulho found in
other groups; in some forms the cavities of the tentacles
seem t<. be united with those of the canals only by exceed
iiigly small orifices, which may be closed, since the tentacles
111 their greatest contraction always remain filled with fluid
111 the neighborhood of the mouth ar,> a number of oral ten-
tacles (Fig. 251, 7') arising directly fron, the oral rin.^ and
.lilleriug from the anibulacral tentacles in not being armn.>ed
in grcnips of three. From the oral ring there also arise" in
Anteaon a uumber of ciliated tubes (.r) which open into the
cjelomic cavity, each one corresponding to a stone-canal of
t h; othei Echinoderms. In AntaJon there are as many as
thirty of these canals in each interradius. and in Prntavrinm
an even greater number occurs ; but in other forms they may
he fewer, Mizucrinus, for exrunple, possessing onlv ftve in all
one being sitna' h1 in each interradius. In the larva of Jnfri
'l<»> there is .,.t tvi early stage only one, communicating with a
I'-rtion of on- >! the primary cielomic cavities, which on its
jMit o])en8 to the exterior by a pore, an arrangement Nvhich
may be regarded as typical for the Echinoderms. Later
iowever, this portion of the c.^lo.aic cavitv degenerates, and
the canal ihi ,i opens directly \nU. tiie ireueval cu-lom, and
t[
ns
communicates with the exterior by th
y the pore. In subse-
648
INVERTEBltA TE MORPIIOLOG Y.
n
queut stages additioual stoue-cauals develop from the oml
riug, and at the same time additioual pores develop iu the
walls of the body, forming what are called the calyx-pores
(icp). These may reach a considerable number, it being esti-
mated that iu Antedon there are uo less thau fifteeu hundred
of them scattered over the disk; iu rjiizocrinus, llyocrinnH,
and Holopus, iiowever, there are only five pores, one pierciiig
each of the oral plates present in these forms.
The schizoccelic system consists of live radial sinuses (Fi-
251, rh) lying between the radial hydroco^l vessels and tl?e
more superficial radial nerve, together with, according to some
authors, a circular sinus surrounding the mouth iuto whicli
til" radial sinuses open. A plexus of lacuna occurs in the
Avails of the intestine, and another surrounds the a'soplui-
gus, ,;his latter in part aggregating itself into a structure re-
sembling r, lymphatic gland and known as the spongy body;
the dorsal organ likewise contains a dense network of tnl)e,s
lined with epithelium. Ahmg the sides of the hydrocol-
canals, in the disk, arms, and pinnules, alternating in the two
last with the triads of tentacles, in the walls of the intestine,
and occasionally elsewhere, there are imbedded in the con-
nective tissue yellowish spheiical bodies known as the hocvh};.
The interior of ench sacculus is lined with cells, and contains
a number of pyriform masses formed of small highly-refrac-
tive spherules, apparently of an albuminoid substance. Tlie
function of tliese bodies is very obscure ; they have been le-
garded as organs for secreting carbonate of lime, as excretory
organs, as parasites, as mucous glands, and lately as organs
of reserve iu which proteid matter may be stored up for
future use. At present, however, the question is an ojn^ii
one, and a function cannot with certainty be assigned to tlicni.
The mouth (Fig. 251, m) is usually situated at the centre
of the oral disk, and opens into a simple tubular intestine
which coils once round the cadomic cavity in the direction of
the hands of a watch and then, ])endiug upon itself, turns
orally to open in the interradius CD upon tlie disk. In .\<-
iinometra, a genus closely related to Antedon, the intestine
lies iu four coils, but there is as a rule little variation from tlic
TYPE ECIIINODEUMA.
649
i" the lower" i^Tr''" """"«'^«"* *J-»- -^tire course
i^jeis ol the ectoderm. The aboral system is
Fm. 253.-DiAonAM of the Arkang^micnt op the Abor.i at
« = arms.
B;- = bmchiul plates. c^= centrn.iorsal.
->« tl.e otJ,er ),au,I, ,„„ch more str„u«ly .levelm,e,l .,,,,1 .t >
"1 mtimate aasociatiou with the ch^imhe, " • ""'''
«"m,,lex-,a, is show,, i„ Fi/252 , i , ■!'/""'«whut
;;'">^l; five str„„K cor,',s rllial o, ,f ^.l , ^ 1^;? ^f™'
""■ plates of >vl,iol, these are compose B tj', '^ "'"""^
K;u.f-l.o«-oells enter into the comn, Litio,, of f *"''
;;.«. ami a oo,„plioate,l »,stem o I ™,,:L ^s^ V'"'
'!« central portion branches are also sen to ^hf • ,'
K.. abh. in s.,.,^e„ forms . brand trverles t ,:'™;;:
'"■' "* "" ""'"'' ""--.'a-yi^K prolonsations of the ^.dtLi
550
INVERTEBRATE MORPHOLOGY.
of the chambered organ. The terminal branches of the radiul
aboral nerves pass to the integument of the oral surfaces of
the arms and to the muscles which unite the various plates,
so that the system governs and coordinates the movements of
the arms and pinnules as well as of the cirri. The epithelial
system, on the other hand, controls the movements of the aiii-
bulacral and oral tentacles, stimulation of it causing move-
ment of these structures in the immediate viciuit}' of the
region to which the stimulus is applied.
Another system of nerve-fibres, consisting of a perioesoph-
ageal ring which sends off two branches to each arm, one
lying on each side of each of the ambulacral grooves, and
which is connected with uerve-libres passing from the dorsal
organ, has been described as occurring, but its signiticauoo
has not yet been satisfactorily determined. No special sense-
organs occur in the Crinoids.
The reproductive organs are developed for the most part
in the pinnules, occasionallj^ a slight development of tiieiii
appearing in the arms or even in the body proper ; in llolopnn
ahme they are confined to the arms. They consist of tubes
lined with germinal epithelium on their inner surfaces and
enclosed within a prolongation of the coelom. They lie be-
tween the two ccelomic prolongations of the arms already
mentioned, and though the reproductive organs are develoj)ed
only in the pinnules as a rule, nevertheless each genital tube
or raehis (Fig. 251, gr) can be traced through the arm to the
body, where it terminates in connection with the dorsal organ.
In their develoi)ni(nit indeed they grow out from this oi^an,
and it seems prcjbable that the (jva and spermatozoa mother-
cells migrate out from it along the rachides to reach matuiity
in the pinnules. Comparing this with the condition in other
Echinoderma, it seems clear that the so-called dorsal oi^an
of the Crinoids is homologous with the ovoid gland of tlie
other forms. The reproductive elements i)ass to the exterior
by one or tw(^ ducts connected with each reproductive mass-
the origin of these ducts is unknown.
Tlie Crinoids seem to liave been closely related to two groups of lonib
known only as fossils. These were the Ci/stohl,i, which apiJeur in the Lkwci
Silurian rocks and die out in the Carboniferous, and the Jilantoids, wiiicii
TYPE ECIIINOBEliMA.
651
nppear in the Upper Silurian and also disannear in fT,. r i •.
For a description of these fonns roforcnceSl'vuf^to Jh^^^^^^^^^
works on Pa]a3ontology. On account of their sim l.dt v f^r> f l r 1"^''^
have been associated with them in the cl ,s '^ ^ ^ *' ' ^"""^^'^ ^^'^^
.l.e groups fonnod an order "^1 i',;^::"^^;' ^'' ^^'-'^ -h of
eoncerned only witli recent forms if .' . ^ ' ' "" ^"'""""^ "'"'"'^ ^^
.•egard the Crinoid.s ."a c,L^ ' " '"" ""^'^'"^ "^"^ —"-"t to
Tlie class Crinoidea has been divided into two nnl,.,.^ ti r> ,
mda^ chiefly Pala-ozoic forms, eharacteriz hn^inei.v ?' H '^'''''"■■
"uder-basals and of a series of nl.,f »'»^'l>all} by the presence of
Pletely, to which u,ay^ d ed t 'u IZ^f "^ f' '''^ '^''"^^ ^-
...ater wldn. of one of the inte .: , r^^^;; ./'ir"'''^ ''''''''
(-0 Fig. .50). TbeiV.0...,,, on tl. olhe ,1 ' ,^, ,11:,^"-^
lonns. te group making its first appearance in tli" M "^"^^ , '^ "r
acterized by the disk bcin.r n.,i,r ;.„. ,. ., 'Hl.sozoic, and is ciiar-
nnder-basa^ and inti^hlds ^ g^X rl^r^::; '^ ^'^^If' '' ''^
width. Transition forms between t it l " o s^^^ ™^ ''' ^^"^' '"
genera H>,ocnnas and Ca/a^.ocnV..., f<,r cCn 1 , ' T'""''' *''"
i'aheoerlnld peculiarities combined with N. ei Id^s 'r^"' '"'"^
satisfactory to divide the class into families only leavh;.: / T'
question. ^ ' '^'^^ '"» ""^^''"^ "ut of the
Development of the Crinoids.—Antedon is tl.P nni n • • , ,
-l-olopment has been studied. The In.n^o lead^ ' "^"""^ "''^^^
tor a time a free-swimming existence, and possesses
a somewhat ovoidal form (Fig. 253) with a tuft of
01 la at the smaller anterior end and five rings of
ciiia surrounding the body. Not far from tl.e ante-
'•i<.r end ,s a slight groove, and lower down uiwu the
.side IS a much larger one. This larva settles down
upon tiie anterior end, the slight depression near
>liis end serving as an organ of fixatl.,,,, and then
a rather remarkable rotation occurs, the large groove
•sii-fting round together with the interior organs until
It comes to lie at the free end of the organism, and at
1 10 same time its lips unite so as to enclose a cavltv
tl)o vestibule. Calcareous plates have ere this de-
veloped in the connective tissue of the embryo and ^^^^^^
outhne a stalked Crlnoid into which the larva is^io. SSS.-Lauva of
gradually transformed, the larval skin shrinking as ^^'■''-
>t were, so as to closely surround the stalk and calyx
Wilde the vestibule opens to the exterior by the
,^nidual thinning and final disappearance of its' roof
lis floor forming the ectoderm of the disk A ft,.,- nr.lr • ■
»».ue time ., „ stalked Cri„„id, t ; , t, aIi^TZI '""T"; ""
.!.< stalk, a„d thereafter leads a free Listenec" ^ '""'"''■' '™
Antedon (combination
of figures by Thompson
AND (ioETHK after Koii-
SCHELf AND HeiDERJ.
552
INVEHTEBRA TE MOEPUOLOO Y.
II. Class Astekoidea.
The Asteroidea, or Starfishes, are all flattened forms, at
no period of their lives attached by a stalk, but creepinj^r
about freely upon the oral surface. In some forms the Ixxlv
is a flattened disk pentagonal in outline {Asterina), but Uh m
usually (Fig. 246) the Ave radii are prolonged out into live
stout unbranched arms, and in some forms, such as Brisimid,
the arms may be long and slender and more than five iii
number. The mouth is situated in the centre of the oial
surface, and the anus slightly excentrically upon the aboral
surface, while the hydiocoil system of tubes is confined, as
in the Criuoids, to the oral surface of the body, except tliat
the madreporiform tubercle by which the system comniuiii-
cates with the exterio? ipou the aboral surface in the iu-
terradius CD.
The ectoderm is throughout ciliated, and contains usualh
numerous mucous glands, while in its lower laj'ers ganglion-
cells and nerve-fibrils form a plexus extending over the entire
surface of the body.
Calcareous matter is deposited in the connective tissue,
but in the majority of forms the primitive apical plates are
not recognizable iu the adult; more usually the aboral ! n v"
e. though upon he marginal and adan.bulacral plate t"
H.e very frequently longer, united to the plates byT rudf
...en ta.7 articular surface and supplied with muscle fibres b!
« . oh they can be n.oved. In addition to these append- „es
..1 the dern,a skeleton, others are to be found in he 8^.,
W.es, such, tor example, as the ciliated spines found i "
le.- forms, such as Z«fc, upon the margin d plates These
^.mes are small and delicate, and gro,';ped togelher ^e
I....e.pal pecuhanty being that thev are covered by an
; e^^ium ol h,gh columnar cells which bear strong ,ia' l"
.o.-t bta.hsh also peculiar structures termed pedlcelhru, are
.•veloped in connection with the skeleton, but'^theb de^,-;
on may be deterred until the Echinoids are under di'cu
......a winch group they reach a high ,rade of d t , ,.
. u.t. lecu nir to certain genera of Starfishes, e.g. /.«,/
tl.e body. 1 hey consist of small columns of carbonate of
I
\^-
IMAGE EVALUATION
TEST TARGET (MT-3)
4
sr J^ MP.,
K
1.0
I.I
1.25
i^g^ 12.5
•S m
ut
u
11^
2.0
1.8
U nil 1.6
^'
'"^
W-
^ # -% ^>^
w
^/W/
m
Oy-
Photographic
Sciences
Corporation
33 WIST MAIN STRICT
WIMTII.N Y. I4SI0
(>i») ^73-4103
4ss
^
654
IN VERTEBRA TE MORPIIOL 00 Y.
lime imbedded iu the coune(3tive tissue, aud bear upon tlieir
free extremity a number of radiating spines, which vary in
the amount of movement of which they are capable iu ditrcr-
eut species. Tlie paxilla are frequently found iu grou})s
around the dermal branchijB, over which the spines may bo
bent so as to serve for protection.
These dermal branchije (Fig. 2o4, h) are pouchiike evagi-
uations of the coelomic cavity with thin walls composed of
ectoderm and a layer of ciliated cells continuous^ with the
peritoneal lining of the cfeloni. between these two layers
there bein^ but a slight developuient of connective tissue "and
Fig.
beei' asserted that the amceboid cells of the coelomic Lain -
TYPE ECIITNODBUMA.
555
iiodifled from
^'^ :'r::- r^r -: ™tt;; : - r-'- "-«
''■■"•eve... n det.n«, .lescipti,;, "si , ft s" ""/, """"■''■
ra.lial ciocmu „f the (li.rpsliv,. f.. , , " •^''■>' ""»» each
»i.ieh, wi,l^tl,eL^ ,"';«''"'•'''■■'' "--'enes (Fi,,. ,,i,
sti-oiiK wall, ,vl,ioh i.s i„ e„n„„n„ . "' '"•""y '''"■'<
l'"rti"u of ti.e ocBlom wlrcl, i. 1 r •"""•"■ ^''"» " "■
;;■■ .; ".e e,„.,,o :,:^;:lx'i:r:r r-' "■« ■-'•
' .«!. .•...lain s|,,„.,.;X,',''^r ','''"'' '" ""• ^»'e'-'"v
means of the muscles of the wall of the ampulhe water can be
forced into the tube-feet, which may be thus extended, a
circular valve occurring in the branch which passes from the
radial canal to the ampulla preventing the water from })assing
back into the canal Contrary to what occurs in the Crinoids,
there are several ai)pendages to the oral ring, iu addition to
the stone-canal. This leaves the ring iu the interradius r/>
and, passing abovally, communicates with the axial .sinus wliieli,
as already stated, opens to the exterior by the madrei)orite.
This isacom])licatod calcar(>ous sieve.plate of some thickness,
and the union of the canal and the sinus takes place wilhiii
its substance, so that in r(>ality the canal seems to open to
the exterior. The embryonic history, and the fact that injee-
tions forced through the tubercle pass into both the sinus nnd
the canal, shf)w that what has been described is the true
TyPM KClllNoDKttMA.
657
H-'la .o„8l.,i,. I„ ti,e w.lls „f tho st„„o-c,„,al culearooas
the surface „.■ the ciliate.l „,,it,,„,iu,„ ,,„i„,. th„„ iu^-ea.".! '
Ihe „,,,,o„,laHe.s „t the oral riu„ are of t«-o kinds, both
he,„« situated m the iuto>>-a,lii, that coutaiuiu;. the stoueia,"
howevo,, usually lacki,,., any other appe^da^e. T, s t e
l-n,s hollow saclike struc:ures opeu 'iiuo the ri.,« by
..."•nnv uock. and are termed the Polian vesicles; thc^Ir walls
-msist of conuective tissue iu which are situated n.uscle
hlnes, and theu- interior is line.l by an epithelium wh „I
appears „ separate and fjivo rise to tho an„eb„id cells of the
|."l.-oc,„l 1 ,„d. The other kind of appendages occur generally
throu^.hout he group and are know,i as Tiedemau's vesicles
c"..s.st,n(; „ n,asses of hollow tubes arranged iu pairs iu oae
;;;■ -- <>' '!»> ".ter..adii. Tho epithe.iunHining 'tl.e wall o
icse s rm..tures als„ . en,s to .-ive rise to the a,„,eboi,l cells,
I ..tl, k.mis ol organs l,e,„g tuerefore comparable to Iv.nphntic
«lands, though the l-oliau vesicles have also been regard !
reservoirs lor the hydrociel Hi. id. "
The „n,»th is situated at the centre of the oral surface of
he disk and opens into a short .esophagus which, i„ some
Tonus, has connected with it ten glanduhir pouches. The
...sophagus opon.s iuto a usually capacious car.liac stomach
"Inch is re,,ucntl.y lobo.l (l-ig 2.55, c), is ovorsible and pro.
vMlcl with specnil muscles for its retraction. Above his
"unes the pyloric stoma.d, which gives rise to Hve radial
P-uches, which son,, branch into a pair of sacculate,! pouches
«e."."g out into the arm,,, an.l being termed th'e radial
la ). From the p.vloric stomaoh a short rectum passes
.'l>.Mally, mterra,l,al ««„a being .somotimes found close to its
w'l ll ?''■■ "™ "'"'":■''•'""• "!>«.« upon the dorsal
^ "face In a few forms, such as /.Mi,,, .-(.,/,,,,,..,„„, and their
•Nhes, the anus ,s wanting, but more usually it is present iu
till! r(><,M()ii indic'uted.
The epitliolial norvous .svHteni consists of a i,lexii8 of
K.iu^' lon-ce Is a.ul fthros i.abod.lecl in the ectodern. and cover
mg the siirfaco of tlio l,o,Iy. and of an oral rin« and Hve ra.'ial
nerves (Fi,. 254, S) which, as in the Cnnoid^are siti;a;;;:; • !
658
IN VKHTMBIiA TM MOUPIIOLOG T.
the lower liijers of the ectoaerm. Upou the aboral siirfaco
of the oral rill-,' and the radial nerves sections show distinct
bands of fibres separated from the rin-like form and do not d(n-elop suckers a( the
extremity. Their walls are richly supplied with nerves, .md
TYPE EVIIlNODEIiMA. ggQ
they ure surrouude,! mid nmy be c(,voiecl in by the movable
spiues „t the iulHinbuhicnil a.ul i„ai-inul plates. That thev
have a sensory function se.mis ch'ar, Init what the evaJt
nature of the function nnty be is as yet uncertain. At the
base of the terminal tentacle of each arm is situated an eye
<'<>UHist.n^ of a laroe number of conical depressions, lined bJ
an ep.thehum contaiuiuK a red pi^Mnent, covered on tlie out-
side by a cutich. and ri cutich^ and these eyes can only c..nvey to the aninnil im-
pressions of chanoes in the intensity of the lij^bt fallin.^ upon
them ; they cannot form ima-es of external ,d,jects
Th.^ repro.luctive o.-^^ans are ten in nund.er, two beiii.^
situated in each arm (Fio.. 2.15, .,). Eaeh consists of a mass
ot roproductive cells, and is enclosed in a genital sinus (Fi...
-.;.4, I), winch, as already stated, communicates rith the axi^l
sinus. Ihe proximal end of each gland is connected with a
<-;dhke structure, the genital eorning later. In later stages two additional arms are developed at the
sides of the apical lobe, which becomes like the new arms destitute of ciii i
and tipi)ed wiLh a group of wartlike elevations. This form of the larvi 'i ■
known as the limchiolaria. ' ' '^
A peculiar process, amounting almost to a metamorphosis, occurs durin.r
the translormation of the larva into the Starfish. Calcareous plates of the
aboral system make their api)earance on the dorsal surface of the stomich
Fig. 256.— Btpinnatiia ow Asleracanthion (after Aoassiz)
an = anus. ],,, = i.ydn.ca'l. m = mouth.
near the posterior end of the body, and oral plates on the ventral surfa. .>
o. the same organ. The.se two systems, at first rather widely senan.l'ni
gradually approach each other, and at the same time the iutonvA or....K
assume the adult form. Finally the two series of plates unite, encl.rsin.^
between (hem the hydroccel, a portion of the digestive tract an.l of tlH> n.^.
""; ,J . T'^?''^ "'""^'' •'""^ '"■•"' •'"« obliterated, and indeed the anl.r-
lor half of the larva takes no part in the formation of the adult animal.
but IS gradually absorbed.
A highly-developed faculty for regeneration occurs in the Asteroid,;,.
the disk being able to regenerate lost arms ; and indee.l an arm, with wi,i,li
u small fragment of the disk is in connection, has the pow.>r of regeii.w.il-
ing all the missing parts. Specimens of the eommeii Starfish Ast.na.s ar,"
in consequence frcpiently found with one or more of the arms bifid a( il-
tip, or even with an abnormal number of arms,
tW^'--'-
TYPE ECIIINODEIiMA.
661
III. Class Ophiuecidea.
.•.oI';^"';;::;:?!?,::;,7,,;^f ':-'•"■«. -emi-e »,« starfishes
i" -ill cases slH,„Ier a,„l HsH,,: ^' "'■"'"' ''"»"'^'»-' »'«>
y 10. 257. -Op/iioffh/pha aculeatu from tiw AT.on*T «r.
I^KKs..^K^. A.C.. z^:::\^:::^^ '" ^"^^ ^"•^
(Th... arms are cut oil close to the disk)
1 = centioilorsal plate. ..
3 = under basals. = ''"'"*'«•
4 = ladials.
face, there are no visible nmlmlnnvni
-liicl. a,e move,,,. Ins 'i,™ ■ f"™',"" "'^ """«•
t»iu e,.oal processes ,>f tl e t . i .i; T" T'll'" "'"' '"■"■
each side of each of the fiv» ? , !, ' ^'"'•""'"""■•e, o.,
tlic oral surface , t ,,1 k 'mii " " """" "'" '■''«" "'
;» the, a,.e ^^U'z a:'z:::^\:'z!':::::jr-
liey seen, to have a respirat,,,.,. f„„„tio„ .„T """"/"'■"«•
''"■ «it of the ,.e„.„a„ctile el^^ent::,',' ;:;,:e"fors:et l^X
662
INVERTEBRATE MORPHOLOGY.
phiura squamata, even serving as brood-pouelies in which the
young develop.
The ectoderm is indistinguishable over the greater portion
of the body in the adults, becoming, as in the Crinoids, con-
founded with the mesoderm. Calcareous plates are largclv
developed iu this tissue (except in Ophiomyxa and its allies),
giving to the disk and arms a brittleness which has suggested
the popular name for the group. The extent to which the
apical system of plates is distinguishable in the adults varies
considerably even in members of the same group, and while
in some forms (Fig. 257) all the plates represented iu the
{Starfish Zuroader can be distinguished, in others only the
radials or the basals or both are visible. At the tip of each
arm is a plate comparable to the terminal of the Aste-
roidea, and iu addition there are frequently present series of
interradials or interbrachials, the most aboral plates of
which separate the radials from each other and extend round
to the oral surface, abutting on five large plates known as the
buccal shields and corresponding to the orals of other forms.
On the aboral surface of the disk above the origin of eacli aim
there is a pair of plates termed the radial shields, whicli
must not, however, be confused with the radial plates extend-
ing ak)ng the aboral surfaces of the arms.
These latter form a complete series extending from the
disk to the terminal plates, and form the aboral wall of the
arms, their lateral walls being formed by another series of
plates, the adamhulacmls (Fig. 258, Ad), while still another
series, the superawhulacrals, form their oral walls. Between
each adambulacral plate and its successor is a pore (usually
bounded by a number of small plates) through which tlie
tube-feet are protruded, the radial water-vascular canals being
situated in the interior of the arm. The cavity of the arms
is occupied almost entirely by a linear series of calcareous
masses termed the vertebral or amhulacral ossicles (Figs. 258
and 2G0, A\ each of which consists of two halves, usu.illv
firmly united by suture. The ossicles are united by well-dii-
veloped articular surfaces, and have attached to them muscles,
whereby a considerable amount of motion is possible for the
arms as a whole, the motion being almost entirely in a hori-
TYPE ECIITNODEHMA.
11 wliicli the
563
/ontal plane, except in Astrophyton and its allies, in which
the arms may be coiled up over the oral surface, in a manner
smnlar to what is found in the Crinoids. These ambulacrax
ossicles seem to correspond with the similarly-named plates
of the Asteroidea.
In the neighborhood of the mouth certain modifications
m the arrangement of some of these plates occur. The two
halves of each iirst ambulacral ossicle (Fig. 258, A ) are widely
separated, and come into close relation with the simMarlv-
separated ossicles of adjacent radii, forming a buccal shield
lie pla e so formed rests upon the aboral surface of the first
adambulacrals {Ad,), which unite in pairs in a similar manner
Ad 4
Ad,
^y^\ Ad,
A = nmb„l„c™l plates. „ = p.|„ , ,„^
Ad = adambulacrals. y _ to,.„g
/ = iutenadial. ^ ^ „,^, ^^^^^^^^^
wr = radial hydroccel-vessel.
forming a triangular plate, termed an oral angle-piece, lying in
an in erracius, and partly covered on its oral surface by a
buccal shield At the sides of the buccal shield are the so-
called lateral buccal shields {AcQ, which are in reality the
second adambulacrals of adjacent arms, and cover in the
second ambulacrals (A,), which serve as supports for the
oral angle-piece. Along the margins of the oral surface of
tins are a series of spines, the hnc<^al papilla, while, at the apex
of the triangle, are the dental papillce. The vertical edge of
the piece is furnished with a number of stout projections the
504
mveitTESBATE iroitmoLoor.
palm angulares (Fig. 260, p), whose bases severally fuse to
form a supportiug plate, the ton^ anyulm-u (T)
Spmes dejeh.ped iu coiiuection with the dermal skeleton,
ea™,g out of ccsKleration the oral a.gle-pieees, ma,- b ™'
tirely wanting, b,,t lu mauy forms they are bor^; iu ™,ti ' 1
rows „p„„ the adambulacrals, aud are usually movable lu
JZZZ7'°"''' ""?" '■"'""""'K ■-'^y bottom ,,e-
cliai hooked spmes are situated ou the oral surface of l,e
a ms towards their extremities, and seem to serve au ad .
::: aS;:,.,:'^''"""'^ -« ""-■"' -^' '- -^-"^t;
The coelo,,, (Fig. 2«0, e) is of comparatively slight e.te.t
he cavity of the ,lisk beiug largely occupied byt^e ige ^v e
t act, and th.at„f the arms by the ambulacra! ossicles, it
disk the cavity IS traversed by numerous bauds which
tend from the body-wall to the wall of the digcstiv-e st
and from the wall of the esophagus a membr nt exteu ^
outwards and orally to be attached to the peribuccal p ate
forming a septum (Fig 2C0, ,), enclosing a cavity surroum '
n.g the esophagus, the peripharyngeal %ac, (^ whiT ,
completely separated from the rest of the c»lo,f \n X,',
thn. and some other forms a second septum occurs pa^
TsZZ''Z"'T''1\T "'*' "'^ I'eripharyngea',:*!
is double. T e coelom of the arms consists of two portion,
one lying on the aboral and the other on the oral side of,'
series of ambulacral ossicles. The aboral cavitv is expand
laterally so as to partially surround the ossicles, but t iT a
lamella, and is thus separated into a series of chambers
Jhicb open into the undivided aboral portion, term d th
aboral or dorsal caual. Au axial sinus, standing in close r
atlonship to the ovoid gland, exists, but presents som.tfel.
tures uot found in the Asteroidea. It consists in A,„p,. Z.
ara ed from one another; one of these is the so-called aL •
pulla (am) of the stone-canal ; tlie second (.) lies iu clos
w u ^hu 'r ?™' •''"""• ^*'"'''' ''"-'"p^'' - '" -i
wit 'tlT "l '^ '", """'P'"-''"™'.^ -mall, and is associated
With the genital cords (;,,•), and the mass of cells in the ovuid
TYPE ECUINODSIiMA.
66ff
f^'laud from which these arise. These two last cavities are
.u d to be portious of the general coelom which become sepa
rated oil dunug development, and are not simple exTensions"
ol that portion of the ccelom into which the stoie-canal opens
m the embryo, and which persists as the ampulla ^
am pc
Fm. 259.-DIAGRAM showing the Relationships of the Stone can*t
Axial Sinus, etc.. in Amphiura s,uunu,ta (arte.- jucBrz^k, '
am = ampii la of stone-canal. ^ ^ ri„g-nerv,
U = geuital bursa. «_.„*, ,'\
mp = madreporite. ^' = Peripharyngeal space.
mu = muscle. * = ^'""*^-
sc = stoiie-canal.
»»». the ..p„„a „, the s.one-eanafo, «,e oThT^ a'^d 1:1^'
Lying on the aboral surface of each radial nerve-cord is
a adial sclmocoehc sinus (Fig. 260, br), which communicate'
.th an oral s.nns surrounding the mouth. The reTatbns o^
.s system are similar to those of the schizoeceli tem „
. ■ 1 « "° r' "'"' "-'r'""' »■— ictions beLe" it
am the ccelomic cavities occur. It contains, however a
sjstem of canals, which correspond to the lacu^se occurring
566
INVERTEBRATE MORPJIOLOG Y.
f i
iu the walls of the oesophagus iu the Crinoids. They huve
been termed blood-vessels in the Ophinroideii, the siuuses
ivhich surround them beiug termed the perihiemal canals;
they follow the course of these latter, a process of the ovoid
glaud coming into connection Avith the oral lacunar ring.
This glaud (Fig. 259, o) is, as iu other grou;)s, im^tly asso!
dated with the lacunar system and partly with the genital
ap[)araius. It lies in the wall of the axial sinus and projects
into it so as almost to till it. At ou(. extremity, as stated, it
comes iuto connectior with the oral lacunar ring, and at one
poiut in it!-' wall it contains a nuiss of cells from which the
genital cords pass cut to the reproductive organs, accom-
panied by strands of the lacunar tissue.
The hydrocoel has the usual arrangement, and is confined
to the oral surface of the disk and arms. The radial canals
(1^'ig. 260, wr) lie on the oral surface of the ambulacral ossi-
cles, extending to the terminal plate, and ending, at least iu
those forms which have simple arms, in a terminal tentacle.
At regular intervals, corresponding iu number to the ambu-
lacral ossicles, the radial canals give of! transverse branches,
which pass outwards in the substance of the ossicles (Fig. 2')H),
and make their exit through the ambulacral pores betweeu
successive adambulacral plates to terminate as tube-feet. No
ampulhe occur ou these transverse branches, though a circu-
lar valve oc(!nrs just where each branch becomes continuous
Avith thu tube-foot. The feet are simple conical structures
destitute of a terminal sucker, and do not therefore serve
for locomotion. Their walls are richly sup])lied with nerves,
uud iu some forujs are i)royided witli numerous papdlii' ap-
parently sensory in function. Surrounding the mouth are
';en buccal tentacles (Fig. 2()0, hi), which correspond to tiie
first two pairs of tube-feet of each radius of the Astor.tids,
but arise by fine braaches, which later divide, and are
directly connected witli the oral ring-canal (Fig. 258, i).
These seem to be undoubtedly sensory and perhaps olfactory
iu function. Th(> oral ring-canal usually has attached to it
iu each interradius, excejjt that in v.hich the stone-c.tnal lies,
a single Poliau vesicle (Fig. '2(50, /*."), though iu Oplnarlh
two, three, or even four vesicles may occur iu eac'a iutcira
TYPE EClIINODEhMA. 5^37
oe Hchizoco'Iip 'Vi,^
".ai r,n« o the nervous system is not enclosed n„„ Ij
.1... c..n.,i, but icmuins m connection with the ectodeL
.t the lower e.trenuty of the ccso„ha«i,s, being .Lued ll.,:
1 1«
1 1
568
INVEliTEBRATE MORPUOLOGY.
aborally by the development of the or«al angle-piecea. The
radial nerves are, however, contained in the wall of the sinus,
coming to the surface of the body at the tips of the arms,
where they terminate by fusing with the general ectoderm.
The muscular nervous system is, as in the Asteroidea, closely
associated with the oral ring and radial nerves, lying on tlioir
aboral surface and separated from them only by a thin layer
of connective tissue. The aboral system consists of a riii.<'
situated beneath the aboral surface of the body, from which
branches pass oft' towards the reproductive organs. ludee'l
the entire system is intimately associated with the genital
260.— Section tiiuough an Oimuuhan showing Sthuctuhe (after
LUDWIG),
A = auibuliicial ossicles. 0 = moutli.
br = scliizoca'lic sinus. p =. pulu angularis.
bt - buccal teutacles. p« = periplmryngenl space.
G = cuiloui. PV= Polian vesicle.
Jf = nuisile. s = peripharyngeal septum
nr = radial nerve. T = torus angularis.
wr = hydroco'l- vessel.
cords, and its course can be understood from a descii))tii)ii
of these structures. No special sense-organs other than the
terminal and buccal tentacles and the tube-feet, already de-
scribed, occur in the Ophiuroidea.
As already stated, the genital cord arises from a groni> of
cells in the wal' of the o\oid gland (Fig. 259, gr) and pusses
in an interradius towards the aboral surface of the bodv,
carrying with it a jmrtion of the axial siuus. Arrived at tliis
point the sinus and cord form riugs, the aboral nerve-ring
lying in the wall of the sinus, while the genital cord lies in its
interior, ftttnplifid in ifa wnll 1)v n lo»p«11.. ,^t -»-^t.. *i,-„ +i „-
From the genital-cord ring ten short branches are given oft"
{UCTUHE (after
TYPE ECUmODERMA. ggg
P-longatif.. of t Lul" St' 1""'; ''^ "-'-"
iu the reproductive poucbe" Ci »' *"""'' ""'' """"«
lobes of the reDrodrtf *^ *''° spawuiug-time the
rushing befr:c'rL:T:L,7;h:'e^ ''''°, '"^ •""■»•»•
.eproductive elements wheurtlb !*"'."■""'' "'"
cavities of the bursm wl,o„„ *i 'lirongh mto the
exterior, or else as In' J ^^ »ake their way to the
From what has been said it may be seen tl.,t n
Astro^Kyton and its a.iies differ ilr^l^Z^tTZ
FiQ. 261.— Pluteub Larva of if.T^ , ■
« = (rs„plmgus ^'•'"««r«M«o« p«;.^„ (after Fewmb)
«= rudiment of adult. '« = momh.
, * ~ t^alciireous skeleton.
™!;:b,e?/1;:i*'^,:;:™^ »™s s„.neti„.es branei,ed and
Peonliarities. CV,„se,,ut„tirtt b l',;' ■'" "'■?""" ""'«''
regarded as consisting of .1 . ,"l''""''""i«" "my Iw
ijK ^i»'^.My.o„, ^^nLr ::„':•«'«: T^r '"''""-
'*"ne, ch of w h,oh « represented by one of the pair.
....ii^ir^LZ"''^::, '"'■•"V'''' "^ '"^ «■="""• '"-'- «
l»"tiu „ther.s the limits of fL fnl , "^'^^^^^ '-^^f^'- -^^^ H
iinutH ot the tubercle may exteucl so an to
672
INVERTEBRATE MORPIIOLOOY.
include all the plates of tlie apical system, and at the same
time the aual opening may leave its position near the centre
of the apical system and become situated in the interradius A /i,
either at the margin of the flattened disklike test, or even on
its oral surface. A marked bilaterality of form is thus de-
veloped, which may become still more pronounced by a mi-
gration of the mouth away from the centre of t^e oral surface
along the line of the radius D, which at the same time be-
comes more or less altered in size and form, and consequently
dissimilar to the other radii (Fig. 263). In these cases it is
possible to recognize in addi-
tion to oral and aboral surfaces
anterior and posterior poles
and a right and left side, the
median line of the body pass-
% ing in front through the radius
'* D and posteriorly through the
interradius AB. Three of the
radii, C, D, and E, thus lie in
the anterior half of the body,
and for descriptive })urposes
these have been termed the
trivium, while the two posterior
ones, A and JJ, constitute the
hivium.
The mouth, which is usual-
ly situated in the centre of tlie
aboral surface, is surrounded by
an area, the peristome, which
has imbedded in it only a few scattered calcareous plates and
consequently possesses a somewhat leathery consisteucj.
An oral system of plates cannot be distinguished in adult
Echinoids.
Fig. 363— a PETALosTrcHous Eciir-
NOID, Britisopm lyrifera, FiiOM
THE AlJOHAL SUHPACK WITH THE
Spines hemoved (after a. agassiz).
D = modified ainbulucnini.
/ = fusciole.
The marked bilateral symmetry referred to above aa occurring in cer-
tain Ecliiuoids ia undouhtciHy a secondary condition, those forms in wiiii'h
tlie Miouth is central and tlio anus approximately so, and wiiose bilati'i'.iliiy
is indicated only by tiie madreporiforin tubercle, being, there is cvi ry
reason to believe, the most primitive. The l)ilaterality cannot be regarded
as a reversion to the more primitive symmetry of the hvrva, since in the
fc>
TYPE EVIIINODERMA.
573
uj vv nch .t is „,ost pronounced are the most Inghly SIC tiatek t^^^^^^^
Projectiuf; iuwarck from the i.mer surface of tbe te»t i,,'
H.e neighborhood of the peristome Me frenuentlv to L f ,
^b.', au), which may either be coiifiue.l to the inter-imb,,! „ i'
Pla es or occur also ou the ambuh.crals, unit u "il it t l!
h lougli w „eh ,,,„ radial hydrocel-caiials ami nerve- ords
V^. In tlie flattened dislclihe forms, sncli as Echi,uZZus
the e ,,1 hxrs are much more numerous, extending fr m the
M ace of the test are nnmerons spines, each of which is
l".ll"wed out at Its base, the hollow fitting over the coi ve.i '
"1 a tubercle npou the test. This b-ill •„, 1 „ i , f """"'y
allows of a fre'e »n,veinent of tl^i^'irtv dif: ■''"''
...nement which is effected by mns'ces «L ,g'";i:
N base Tiir "1; "'"'"'' '""' '"'■""■"« " «'-"' a i.,™^
s base. The spines thus serve as eflicient organs of locorao
t . n, usurping this tuuction entirely iu some forms w Tn
others they are ahled by tli,i tube-feet Thev 1 ■
'...■",„ serve as defensive ■:truct„rcs, allt ^^,^1^:^:
a e l,mg and slender and readily penetrate th, U "f less
p.-otected animals, or in .«/,»„„.„„.„, ;„ ,,,;„„ \ ^ j-^
674
IN VEBTEBIi A TE MORPHOLOQ Y.
spines are soinewliai; eulargeil towards the tip, the enlarge-
ineut contaiiiug a poison-gland whose secretion is injected
into the wound produced by the spine. Pedicellarise, which
have already been noted as occurring in the Asteroidea and
the Euryalid Ophiuroidea, are richly developed in the Echi-
noids, more especially in the neighborhood of the mouth aiul
anus. They assume varying forms, in the typical one (Fi p-C
Owing to the presence of the firm test the muscular system
\Ul Hi'
Fig. 265.— Diagram showing the
Al = Aristotle's lantern.
g«"l ".'S the stone-ctnal
W passes aborally to open into the axial sinus close to the
^adreporiform tubercle, and in addition in the lad al Ectf
noids the ring has attaehe,l to it in each interradius a pongy
rncture which is usually termed a Polian vesicle Zf
ongh t ^se structures in other groups are saclike The
abe-feet (y) which perforate the ambulacral plates are in tl»
uajori(,y of forms, and especially in the radial ones v ry
eUensible and provided at the tip with a sucking-disk, and o
assist he spines in locomotion. Two pores as a me exist
or each oot ; through one of these the branch issuing ZL
0..ck tiom the foot mto the interior of the body to terminate
m a saclike ampulla. The feet, however, near the a K,r 1
.urlaoe are frequently branched and lack a sucker, .^eivbg a
c piratory function rather than a locomotor, and in the
only on the aboral surface of the test, nearlv all the feet may
assume a tentacle like or pinnate form and become respirator/
The digestive tract in all those forms in which the mouih
-cupies the centre of the oral surface is provided with a
578
INVERTEBRATE MORPHOLOGY.
li '4
pharynx surrouucled by a complicated calcareous masticatory
apparatus usually termed Aristotle's lantern (Fig. 265, Al, aiul
Fig. 266). Wlieii most highly developed it has the form of a
pentagoual pyramid, whose apex is directed towards the
mouth aud consists of five similar portions united together.
Each portion contains an elongated ribbonlike tooth (Fi(^.
266, t) lying in an interradius and projecting slightly beyond
the lips of the nouth, though for the greater portion of its
length imbedded in ;i calcareous
socket or alveolus (a) composed of
a right and a left h;i]f united above
by epiphyses (e). Between each
pair of alveoli, at their basal ends
is another calcareous piece termed
a radius, and below each of these,
i.e. on its oral surfaces, lies another
piece, the radula (r). Muscles pass
to this complicated apparatus from
the auriculse and from one piece to
the other, producing approximation
and divarication of the projecting
tips of ihe teeth. The presence
of this apparatus brings it about
that the circumoral hydrocoel and
lacunar rings are forced back some distance from the moutli,
surrounding the oesophagus just where it leaves the lauteru.
It seems well accordingly to speak of these rings as beiug
pericesophageal rather than circumoral.
On leaving the lantern the dieostive tract, starting in the
interradius 1)E, passes around th'' coelomic .'avity in the direc-
tion of the hands of a AvaLcL, until it reaches the interradius
CD, when it bends abruptly on itself and, on another pluue,
nearer the aboral surface, retraces its course almost to its
point of starting, whence it passes to the anus. The portion
of the intestine immediately succeeding the pharynx is termed
the oesophagus aud is succeeded by a slightly wider intestine,
the junction of the two parts being in some forms furtlier
indicated by the occurrence at that point of a large caecum.
As a rule, however, appendages to the digestive tract are rare,
Fia. 268. — Aristotle's Lan
TERN FKOM Avbacia.
a = nlveolus.
e = epiphysis.
r = nulula.
t = tooth.
ii .if
TYPE BCamODEKMA.
67»
th. oiily one occurriuB with any ,„arked ,lw-,.„e „f coiiHtam.v
l.en,K the mphon (Fig. 265, «•), a tube which aiiseVf™' !l !
-sophas„s an»«u .uto .t at the extremity of ti,e oral coil. Th fuL ion J
t t if """"rro-". to be respi..atory, but it is to b ^
that It 13 wanting m all the members of one of the or,le,-«^H
ay^astroir '; : ""■""■^^^■»'«'» '--^ 'l'" ---l arrangen,ent
consisting of a perioesophagea ring (Fie w.r, ...i .,f , „
radial ooras M. As m the^phiui-ijl^l^.t; t e '2™
ith , H r ' '"™ "'^"-'''^«» *■'■"» «« ectoderm and s uuk
«lthi. the body-eavity, and accordingly there is to l,e fn ,^ 1
an epineural sinus lying below the i"ve-c X. Be ol he
nerve-ring, however, no sinus is to be found ■ nd ./
cttr":^" r T" ;r i"' '"^ ^^^^^^ :;:'::
liie extiemity of eacli radial cord fuses with the ectodenu in
SI t:t^' Tn ^" '^^ "^"^^^ ^^^*^' -dt t:;,"
uted to the walls of the terminal tentacle. A muscular
uerrous system is present, consisting of five mM.t« 1
the aboral surface of the radial njJJll t ^1 rtW
s\ th^^r'^^-ti ""''^r:^ ''-''' - ciiLct^rec^i^z
utli each othei , they send fibres to the muscles of the mas
w^Wh^ pass to the walls of the ducts It the T^tduX:
Sense organs of various kinds have already been referred
o, such as the terminal tentacles of the hydroacl canals he
fascioles, and the splneridia. In addition to thei „t me
spots occurring on the ocular plates have be n r^VaS as"
eyes, and somewhat complicated structures of a br ght blue
color which occur abundantly over the surface of t l.l
a .P~f .>,We„. have also been regarded l^eti;"
--e-ul/"-! l'"' '7T- "" '^"•■°^'™'"'' -y^'em consists of the
ge-ital «,rds and the reproductive organs. The former hnve
their origin from a single cord, which is a hollow t„be ltd
mo
INVEHTEBRATE MOHPHOLOQT.
iuternally by immature germ-cells aud i.s connected at its on,!
extremity with the ovoid gland. It passes thence to Uie
aboral surface of the body, where it forms a ring (Fig. 26G, r/n
from which in each intorradius a branch passe:-; outwards to
expand into a highly raconiose sac, the reproductive org.ui
{G). In some forms the number r,f the organs may be^v.
duced to lour or even to two, though live is to be regarded ;is
the ypical number. Each organ oi)ens to the exterior by ;i
special duct {Gd), usually opening on a genital plate, but
sojuetimes in au int^ -radius outside the genital plates.
As already noted, there is considerable variety in the rela-
tive positions occui)ied by the mouth and anus, and many
diiierences of structure are associated with these variations.
It IS possible, in fact, to divide the Echinoidea into tlir, ,.
orders, which are marked out by the positions of the opeuin-.s
of the digestive tract. "
1. Order Desmosticha.
In these forms the mouth occupies the centre of the oval
surface, and the anus approximately that of the aboral sur-
face, the radial symmetry usual among Echinoderms beini;
well marked. The body is usually more or less spherical in
form, though occasionally soraew)iat flattened ; all the anihu-
hicral ])lates are perforated hn- the emission of tube-feot, and
all live ambulacra! areas aie equally deveh)ped (Fig. 202). In
the members of this order, conseijuently, the bilateralitv is
marked externally only by the position of the madreporifi.nn
tubercle.
The prinniry ambulacral |)lates frequent] v fuse to form
secondary plates each of whicli i.s i)crfoiated by several ])air,s
of pores, as nniny as six occurring on some phites i., AV/v^m/y.
locenfrnfits. The spines are sometimes exceedingly long.'/is
in Diiuhnw, and are usually well developc^d. being hi Arh„'m
equal in length to about half the diameter of the bod v. The
auricuhn are the only representatives of the calcareous i)lafos
or bars which extend from the oral to the aboral surface, and
au Aristotle's hmtern is always w(>ll developed, its ahv..|i
being much longer than broud. In this order external brauchio)
TYPE ECIIimDEUMA.
-0% tl.erefore, to clivide the orT ! "'^^'"'- ^* ^« «»«t<>m-
ENTO.K.XCHU.., i,,, „'^.:C^,:;^'^ ^- sul,.,.oups: the
ATA, iuclnding all other fon s fudT V^'^ "^' J^ctobiunchi.
2. Order Clypeastroidea.
•■".'"» ■■« situate,! iu t! . in e' !Z :« .T '"■"' l"""' '"""«'
"f tlie flattened test •, ■ i, A' ; ', ' """"" "' "« ■"".■.-(«
'"•" siuface, as iu JM,V,, i,, '• **• ''"'>' "'■ "u Us
«4.7«a*.tl,eb„.lyis|,„t»ii,,|,t,
('■•'tteued, but iu ti.e t,v„ otl,er
Jjeuem nh-eadv n,eu,i„„ecl the
fl.-.tteu,ug is eaiTied to such „„
"■^'7" tl,,.t the test has „ ,uo.e
" ess .hsklike shape, wl.euce
"";'""" ^'"'''-'"""•"•s a,,,,lie,l to
'•ortniu foruis.
1.1 aocordauce witi, '.he shift. -^.- 'V-Pf^Si^
7 "f '1- «..»» fa.u, the centre ^\*^^^*^
l,,,'" "l^;""' ».v»te". cert,.iu'":-"--'*'".vp..:.v»r „,:,„,.
'l''-"Ke.s take plaoe i„ it, t,.e .Z f"'"""'""""". ,».,„",
■;p ma,ke,I heiu« au e.teusio, «;:.,. r.,,t,;r',;;„ «---^
i-- -.oiu« We?": sr ortr;' '"■ "'""■^- "- --■"
:""'-l-eral plates, au., iu si™,'"'" "" ""f ,"' "- i"te,-
"""■■•■'"lius .//,au,i the eonesn ,< , I'"™,""'"' l««t«i.,r
» ■'"«"« (/:W»-„,„w/,„,-,„) The ' .'■"'"■'"'"'■'"•" "W". is
"'■" "» " .-"h, eouHue,! to the .il'" '."'"'"''"'•'■"' I'l'"""
»'"f-e,thep,a,e,ueaMho 1 '■''''■''"" "' ""' »I'"™I
"'" "■•"> ™rfa..e heiu, tp.^^^ L"' "," "'»' ",■"' "-" " ■
«i" of course v,„.y uar,;>v a , ;.„, l";" ••!':"'"««' i''"l-H
f(''H(Iiially onj.t!
«'viug thus the appear
o'" fi'^ tiu3
»UNM
•aiice
npical end <,f th
;7PH«MtowardHtheod^eof th.
'I live liower-petals, aud h
e oerioH, -mhI
!i(^ tesf,
oiice
682
INVERTEBRATE MORPHOLOGY.
the ambulacra or areas occupied by perforated plates are
termed petaloid. lu Echinanichnius, for instance, the })lutes
after having reached their greatest widtli retain it to tlieir
abrupt termination (Fig. 267), the petals being then termed
open, but in other forms, e.g. Jlellita, they contract again
l)eripherall3', in which case the ambulacra are said to bu
closed.
The pores belonging to each pair are generally united by
a groove, and are termed yoked pores, and iu Mellita, for
example, in addition to the pair of yoked pores on each ])lato
there is a third one situated near the middle line of the am-
bulacrum. The tube-feet which project from the yoked jujres
are frequently pinnate in form, while those emitted through
the single pores are simple and tentaclelike. The spines are
generall}' very small, though those of the oral surface serve
for locomotion.
In Mellita, towards the periphery of the test, the imper-
forate ambulacral plates of the radii A, B, 6', and E ([.o not
meet, leaving elongated holes passing through the test, and
the same thing also occurs with the plates in the interradius
AU, so that altogether live such holes exist. In other forms,
instead of holes, notches occur at the margin of the test, ami
other interambulacra than that in which the hole occurs in
MelUUt nniy be atlected. Calcareous columns extend from the
oral to the aboral surfaces of the test, being especially almn-
dant towards the peri|)hery, and calcareous plates uniting the
two surfaces occur on either side of each and)ulacrum. Au
Aristotle's l.mtein is present, but the alveoli are usually
broader than long.
3. Order Pettlosticha.
In this order, as its name indicates, the ambulacra are
usually petaloid, ami the bilaterality indicated in the Cl\ |i( as-
troids is more pronounced, since neither the mouth nor tin'
anus rical surface. The anus lies in the posterior inttuiailins
yl />, while the mouth has moved forwards to a greater oilissl
extent along the radius D. The test is oval or, freijui iillv,
TTPn BcmmmHMA. 533
somewhat heai-e-shaped, owintr tn fl,„ . •
■"o>-e or Jess depressed ol to ,,.™ ' ""^^' ^ ^^^
The madreporiform tnl», ? ? " *'™°™ (^W 263).
-"'.e of the ap ea Vstrttr r'' "^""^ '"'-«'' «^«
""■« 'iividf,.K the'apiea?:^;;,, "'"*'' 'T"°' i-i<^^r.ai..,
« obliterated in ail members of .,^''%P"^'''™>- gemtal pore
live glaad ™.respo„di2 to .t dt/ ' """' **"> '■«P'<'^uc-
>«pi-oductive orRans aid ,1 <'"'''PI""'r3. so that but four
-«e forms, ho^te , « e redToLT ,T'"' <*'"'"''-)• I"
»'"'. pores is carried tilf furth 7v t '!'^';''P^°d»"«ve organs
|i«ht anterior iuterradius^XftlT' TT"™"^ '" "'«
...terradins Z^^' may also disan^r /"'^ " '"" ■""«"<»■
■"« pan of the n>ad^eporif' .^rbtrersoTh'r'/'''^ ''^^°"'-
■■.■productive organs and nlacru,u All There is L^ a w''^"^" Posterior inter-
l^etalosticha. '" "° Aristotle's lantern in the
l>eoelotment of the Echimidea -Th„ » , '
"•""••OS very .si,„ii,„. t„ that of ho rw '.'?^"'"n'^^"t is i„ if., general
Ml. prroneoU j;:.:;:^^^^ eases be .is:;: „ J:!
"" I <>.st.M-i,„. ,,orti„„ „f eho body whip . . ^"^'"'''''".'/'^v) processes „no„
«"' ''"•" occur „,,ou th, ,i,,,., ,,; '/ ■ ^'^ t«-ooarliko lolu-.s fri,,,^.,
- "own as Ciliated epauiett:.";: ^ T'^ ''"^'r" "^ ^"« '>"" -
PoM.Tior portion of fl,,, body of the ..r"^ •'""■"'"" '^^'^'^^ i > the
'" ;-olH.ion.s,nps of the vario, ,' , ^v' '7'« '<''-'-"'".V 'Vsorbed.
I *'i'' ':eod not b(, ji^Hiii -li • ■ *»"*"!'« "Jive already l.e".. -' - ■ ,
T i
684
INVERT EBlt A TE MOliPUOLOG Y.
primitive, while the Clypeastroidea and Petalosticha are secondarilydo-
rivi'd forms. The bihitcrality of these latter forms is not to be regarded,
therefore, as having any phylogenetic significance.
Class V. Holothuroidea.
The Holothurians (Fig. 268) are characterized so far as
tlieir form is concerned by being elongated in the oral-aboral
axis, having thus a somewhat wormlike form, the mouth be-
ing at or near one extremity and the anus at the otlier, exee])t
in the genus lihopalodina, in which the two oj)enings are ap-
proximated. As a rule the l)ody is cylindrical, but in some
forms, such as Psohm and the /iUmpodd,
there is a well-marked flattened ventral
surface. Three of the radial hydroco'l-
canals lie upon this ventral surface, the
other two being dorsal, and it is usual to
a])ply the term trivium to the ventral radii
and bivium to the dorsal. It must l)e
recognized, however, that this use of the
terms does not imply a homology with
the radii similarly named in the Ecliin-
oidea, since in the latter the radii (', 1),
and A' constitute the trivium, whereas iu
the Holothurians it is the radii J, U,
and K
The mouth is surrounded by a circle
of tentacles varying in number from ten
to thirty. There are at first five primary
(Zoflrt. A IloLoTHiiuiAN. t''"t''^^*l^'^' iJiterradial in position, wliioh
are formed in connection with five ca'cal
outgrowths of the h3'droco>l-ring, and the tentacles subso-
t^uently formed receive branches from the five primary ca'ca.
In shape the tentacles vary considerably, being cylindiii'iil
iu some forms, arl)orescent or pinnate in others (Fig. 'iCKSi,
and in others peltate, and iu some forms they are retractile.
The exterior of the bod}- is usuall}' covered by an epithe-
lium over which a cuticle may be developed, but iu some
forms the ectodermal cells siid; into and become fused with
the subjacent connective tissue. The calcareous skeleton if*
Fro. 2QS.—Pentacta fron
585
TYPE ECIIINODEllMA
1 , » , , ■ woo
skeleton is represented by llJZZ' TTZ' "" "'"— -
I'orforated, tuobbed, so„Jti " , If t "/ ™""- ^'-1-S
".■ associated with au auchorii e ^''*"^. "' '" <^'''"-odo,a,
a.e uot suffieieutly r,.„„ro„ ' 'r^ spicules iu Synaptu, aud
"»"t, which i« 6V„„w" Z *^ ^ ■ "«"'"^ '° "«' i-tef-u-
Tl-e isBoi-KlicatlrofarCr. ': '"'" '""• *--'--*.
WfenV. a circle of fi™ phte ^' "^ "^ "'*'*' """-fi'' '"
0-1 syste,,, is represented t T"""^' "'" """• >"" "'«
Piates which may be cWd 1 '',""■'""' "'' ^'~'"« ^y five
I" other parts of the hlZl'tt'T'' """ '-'-'-•
■"•■'tter is also frequently iL u" , ""*'.«r<^'" calcareous
'ive tissue of the wall of ft ^1"'*?' •''■ '" "'" ""'"'-<'-
«-lial ossicles, gro ,ved o .W TT'"'' '^'^''"""y •>< «ve
:-n.ydroca.l.catal»;rud yCi!: r ,"" '""'"' """"^
"'« with them, thouJh iu tlK„!7 """"•"''f ' "■''««1«» alternat.
'^..t-.es is greater'th,: Ttl ™rb:r''f h'" """"•- <"
«s»icles may be increased X, ^ ^ "'" ""^'ra-Iial
"-seutery, au,l i„ son efn,,^ Its'" "'' t" '""■"' "' «'«
•bvelops in the wall TZ T ' '^ T "'"'''' "''^''"'^
I'Wseut, though the plates of ^7 •""'■. ''"""' "" '•■"■e'y
otlier forms bear tlim td ,f "'r"'""' ^"'"'''"' ™'> " '«*
The ca,l„n, is trav ; ed b^ eT ,"'" "'" ''""'"'^ "'-«"«■
'lisostive tract to th ".> 'ti M •""r"'"'*- uniting tl!;
-ailed dorsal niesen:^-'^^ ";,;";: 7.»'-'. ^-ing the
■"' ■no.- portion of the ini radius (V^tI'"'' 'T '" "'«
«'l<>m which surrounds the o-o, , , • '""""" "*' "'^
'«t, as in the Echinoid 1 „,;''«'" ''< »"';"■"'-• '■-" the
'"•' -.ilariy i" son,e forms Zt 'J^l^'r^"^-'^' »P"ce,
hpaco surrounds the lern.i, al , , ''"'""""■'")" Perianal
'■' ^map>a and its alii " , ' IZ T f ,",'" '"«''-''"™ "«'.
586
INVERTEBRATE MORPHOLOGY.
\
of the Crinoids iu maintaiuiug a circulation of the coelomic
fluid.
So far as is known, the portion of the coelom which in the
embryo opens to the exterior by the water-pore and with which
the stone-canal communicates in the Asteroids and Echiuoids
does not persist iu the adult Holothurian, and consequeutly
there is no axial sinus, and it is doubtful if a structure com-
parable to the ovoid gland of other forms exists. Schizoca-lic
sinuses corresponding to the perihaeraal canals of the Echiuoids
occur in their usual position betweeD the nervous system find
the hydrocffil-canals, and consist of a ring accompanying the
nerve-ring and five radial canals which abut against the ring
at their oral ends but seem to be completely separated from
it by septa. A lacunar system is well developed, consisting
of a plexus in the walls of the intestine, the various branches
uniting to form a dorsal and a ventral intestinal vessel, which,
passing forwards, unite with a lacunar ring surrounding the
oesophagus at about the level of the hydrocoel-riug. From
this ring five radial lacunte extend backwards, lying in the
connective tissue between the radial perihsemal sinus and tlie
hydrocoel-canala, and giving branches to the tentacles and the
tube-feet. A lacuna also extends from the pericesophu^^Md
lacunar ring to the reproductive organs arising from a thick-
ened portion of the ring, and this thickening has been re-
garded as the rudiment of the ovoid gland.
The hydroccel has the usual arrangement, consisting of a
ring (Fig. 261), o) surrounding the oesophagus behind tho ring
of peripharyngeal ossicles, and having arising from it a stone-
canal which in tho majority of forms hangs freely in the
coelomic cavity, where it terminates iu a madreporiforni ]tlate.
Iu the embryo it as usual opens upon the surface of the body,
and this condition is retained in many Ehisipoda, in wliich tho
canal opens upon the dorsal surface of the body, probuhly
indirectly through the intervention of an ampulla, as in other
forms. In the majority of forms, however, the connection with
the exterior becomes lost, the ampulhi which is present in the
embryo disappearing, and occasionally a number of secoii '*» f^om the
tnviumoftheEladpoda; wLu Z." ! T''""' ""■" "' "'«
"l™g the lines of tlTe ra. iaTotn ? ''"^ ""^ ''« "^''ged
208) or naay be .eat er: 1 ^Xit ""T*"' ''''^'^' ^'«-
body (Tk,one). In form tW a —'"■ "'^r'''"'« "' "'«
e.tljer simple fingerlike processes o7 T'"!^''"''''^' "'^'"g
sucker. Frequeutly the tnbe Iff '^ ''I'P'"^ ^""' a
".e Elasipodl the/talTe tfe form "oTsr' '"^'^f'- """ '"
corneal processes arranged in pairs ^^ «-ell-developod
Owing to the absence of a firm lest in n tr ,
tl.ere is a much more extensive del ! ' ^"'"""•rians
8.vstom than in other Echlnodermr tI'™"" "' "'" '""^^'a^
body-wall is formed by a layer rfci J l" """"■ ""*■'"' »' "'«
0" each side of each radi,tf Wdro " "' "'•"•'"'"'""•«^' ""d
muscle-bnndlo (Fig. 269, „) rom L.t^ " '' " '""si'-'taal
'»'"<"«« pass to the p;r1p „;"!elf "'-T' '""'"" "l'""'*'
■■ee^ctors of the tentacles aSh-dir"'^^ """ ^""^ ^
As staled the mouth is usualN f
'""'y at the centre of a dk™ .•,;,";", ™'™'"'- '^'"' »' "-
'" tl.e Elasipoda it has a so ,"« 1 f " '""'"'o^' '™'
•gestive tract is a simple tube '"hi , ' ""■'*"''""- T''«
'"•tlj straight course fr ,„, mZhl "'T"'"'"^ '"'« a per-
" '»bent twice „p„„ it. 1 ",:;";': ''""""■■« fequeitly
-"Ji"K limb (Pig. 2fi9,/>,'.„ a t tr^^^ "" «"'-ior de.
'lexeendmg one (/,). The term!,, J n*' ^''}' ,""'' " Posterior
, --"■■« li."b is dilated, t i ; / *^^ ? f" P"^'"''"' •'«-
.l»H,cle-bands(^)rad,^aet,.tl,.!r.,';^'?"''l')f™'« whose wall
'Hiythmically contractile, and lar^ltrtj^^^^^^^^
588
INVERTEBRATE MORPHOLOGT.
the SynaptidsB two much-branched structures termed the re-
spiratory trees {k). As their name indicates, these structures
are supposed to have a respiratory function, but it is possi-
ble that they may also aid in excretion, the waste products
of metabolism collecting in the cells lining the interior of the
Fig.
269.— Diagram representing the Internal A«Ai'oAi;
THUKIAN (after Ludwiq from Leunis).
^'^0-
i' = cloucal opening.
k — respiratory trees.
I = Cuvierian organ.
m = dorsal mesentery.
n = duct of reproductive orgau.
0 — reproductive organ.
p — lougitudinal muscles.
a = tentacles.
b = calcareous pharyngeal ring.
c = hydrocoelring.
d = stoiie-cauals.
e = Polian vesicle.
/, g, h — intestine.
i = cloaca.
9 = radiating muscles of the cloaca.
tubular branches and being carried to the exterior In ii-
desquamation of the cells. In addition in a small number of
forms {Holothuria) there occur upon one side of the cloucii a
large number of slender tubes (/), which, at the will of the
animal, can be evaginated so as to project through the aiial
opoiitjg. These constitutG the orgau of Cuvier, the fuiictiou
of which is not as yet satisfactorily explained.
TTPB BOHlSODEttUA. 589
The epidermal nervoas system consists of a perioesoni,,
geal nug aud five radial nerves as iu other forms !udTu addT
tan hve ,nterradial nerves pass from the ring to be tent^l '
extremities passing tUrongl, the tissues of ILIo,^:,-^,":^;;;::
».th the ectoderm. In accordance with this arran Jmen tan
epiueural smus accompanies each radial nerve thou^r„\! \
^"m the pericesophageal ring. The mnsculaV ne^U .^
.ervous system has bee'n dLoverot in'Ihe H^lt ir^-'
uthal lieive close to its origin from the rinrr T?, i .
..nteins . number of otolith! and I t:t^^^X
^^^.uch greater, amounting to ajuf t^CsuL" r;:. ^Tf
The 8.ynaptids and Molpadids are hermaphrodite bnt nil
other Holothuriaus are bisexn-.l Tl.. «*F"iou te, but all
(Firr 9fiq ^\^ . 7 '^^^^*^^"'^^- Awe reproductive ortraus
590
INVERTEBRATE MORPHOLOGY.
- r. :
(lifFerences are associated with the absence or reduction of the ovoid ghmd
and of an aboral nervous system. The number of the organs is very much
reduced, and no genital cords have as yet been discovered. It is interest-
ing to note, however, tlie existence of a genital lacuna mentioned above,
in association with which the reproductive organs seem to develop, and it
may be, as stated, that the lacunar thickening from which it arises 'is to be
regarded as representing the ovoid gland, which, as has been seen, is
intimately connected with the lacunar system in other forms. It seems
probable that in harmony with the shortening of the stone-canal and its
separation from the body-wall, and with the abortion of the axial entero-
ccBl, there has been a shortening of the genital cords so that the aboral
ring no longer exists, and the reproductive organs, reduced in number,
develop directly upon the wall of the genital lacuna. It must be remarked
that in some forms there is no distinct genital lacuna, but the reproductive
organs are associated with the intestinal lacunae, a condition which may
be secondary.
Development of the Holothuroidea.— The typical larva of the Holotlm-
rians is known as the Auricularia (Fig. 270), and is distinguished from
that of the Asteroids, Ophiuroids, and
Echinoids by being destitute of armliko
processes. In later stages the ciliated
bands fuse in such a manner as to form
St a series of circular bands surrounding
the barrel-shaped larva and recalling tlie
<'P larva of the Crinoids. By the gradual
elongation of this larva and the disap-
pearance of the ciliated bands the adult
form is acquired, there being no absorp-
tion of any extensive portion of the larval
body as in the Brachiolaria and Plntous.
The Phylogeny of me Echinoderma.
—The Echinoderms form a well-defined
group siiowing little indication of aflini-
PiG. 270— Auricularia Larva OP ties with other forms, and the establish-
Synapta (after Semon).
dp = ciorsal pore.
-fir = hydroccel.
pt = primary tentacles.
at = secondary tentacles.
ment of a plausible phylogeny is an
unusually difficult task. One tliiii;,^
however, seems certain from their de-
velopmental history, and that is that tliey
have been derived from primitive bilat-
eral forms, and that the radiality charac-
teristic of the adults has been secondarily acquired. The larv* are strictly
bilateral, there being indications that originally two water-pores, situaled
symmetrically upon the dorsal surface, existed. The first question to he
decided then is the cause of the radial symmetry seen in the adult.
Bilaterality in the animal kingdom is usually associated with an antoro-
popterior differentiation, and this with a definite axis of progression, 'i'lnis
TYPE ECHINODERMA.
691
become specially provided with sense oZTf' m"^ ^^"^^^'^^"tly it has
new conditions whether favorable ouJro''' ''''''^^''" ^^ ^h«««
affecting the dorsal and ventral su^facf^^^^^^^^^^^^ '"!"''*'''^ "^« conditions
dorso-ventral differentiation exists „.. ?*"''"' ^"^ consequently a
affecting the two sides ofXb 'y ^^l;" o ? " T^ '"^' "" ^''"'^^«-
the differentiations which occur on each side If h' "''''' ""' c««««q»ently
con^:^::;^-: ^~ ^^" ^~tr ^^ -^^^
.-sion or w^atrod^ ^i^rar fh'e ^^"^ """^ ^ ^f pro-
radiahty of the Echinoderms may b Ihe re u ^ ^ f^^'''' '''''' ^^^^ ".e
larva The majority of recent /ch noderrarp > "^f""'' '' "^^ ^^^^'^''^l
f?rr '^•^ '"^"^ ««^i'«' but it wm be fouTd I 'I '"'' '''' ^«™«' t'^e
foms are the latest to appear, and tC the Pp,. * geologically the free
actenstic of the Paloeozoic ro ks. Ths would T'" "'"' ^^P^^'^"^^ •-'''ar-
0 be regarded as the most perfect representltir'' "^ ''"' '''' ^"^^^^^^ ^^e
he ancestral types, an idea Ihich is borne on/h """"""^ '"^^^"^ ^^r^n^ of
derm development. Thus the calyx of the p"^ '''. ^'^"'^ '" ^^^^^^o-
posterior portion of the oval larv^ fh *''^^"'^o^d is developed in the
|hest,a,k; intheBrachiolarTain/SuteLtr^.r"^" '^'"^ ^-P-^ t
1" the posterior portion of the larl 'ti/ '•"''"^' '^'^'^^'^ ^^^Wd
' ser., v, 1887.
0. W. Field. Th, rarva of Asteriaa vulgaris. Quarterly Jourual of Micro-
scop. Science, xxxiv, 1892.
ornn7noiDB.\.
Th. Lyman. OpJiiurida and Astrophytidiv. lllustr. Catalogue Museum Coiup.
Zool.. 1865.
B. Ludwig. Beitrdge zur Anatomie der Ophiuren Zeitschr. fUr wisscuscb,
Zool.. xsxi. 1878.
H Ludwig. Das Mundskelett der Asterien und Ophiuren. Zeitschr. fUr wis-
senscb. Zool., XXXII, 1879.
H. Ludwig. Neue Beitrdge zur Anatomie d$r Ophiuren. Zoiischr fQr wis-
senscb. Zool., XXXIV. 1880.
TTl>ll KCmmDKHMA
/i95
xxm, 1889. ^mmen u,ul Crmoiikn. Jcuaiscbe Zeitsclir.,
E. W. MaoBride. 7%e Development of tJie (Umtni n
and Aboral Sinuses in Amphium 1 ^'"f"'^^7«"*. Ovoid Oland, Axial
euce. XXXIV. 1892. ' '• Q'^'"t«''.V Jour.,. Alicrosco,,. Sci-
ECHINOIDEA.
;■ "M^t- ,£ rrrMlsi^r,^' * * — - .» ,„.
■ S...f!"t^.'"' "• *"•■'•*•• K»"8>. 8vo„a.. Vetc^k. A.„„
UOLOTnnuoiDKA
0. Hamann. Die Ilolothurien. Jena, 'ibn/'
H. Ludwii Die ^.„n,, ' , *-'^'''-"- '^<«j'"«:ie, Lvn. 1894.
596
INVERTEBRATE MORPHOLOGY,
CHAPTER XVII.
TYPE PliOTOCHORDATA.
The type Protochordata coutaiiis a u umber of forms which
present certain features of similarity to the Chordata (Verte-
brata), oue member of the type, AmpMoxus beiug frequeutly
cousidered as belougiug to that group, which is to be regarded
as the most highly ditfereutiated of all the types composing
the Animal Kingdom.
The various groups of the Protochordata differ greatly in
general appearance, but certain structural features of great
morphological importance are common to all of them. These
may be briefly stated as (1) a notochord, consisting of a more
or less well-developed rod, arising from the mid-dorsal line
of the digestive tract and either extending the entire length of
the body, or else limited to its anterior or its posterior^part,
or even present only during larval life, as in the majority of
the Tunicata ; (2) hramhial slits which place the cavity of the
pharynx in communication with the exterior and serve us
respiratory organs ; (3) a central nervous system, situated in the
mid-dorsal line of the body, and arising in some forms as an
ectodermal invagination.
Metamerism is but feebly indicated in the majority of
cases, some forms possessing only three mesodermal somites,
while others, such as some of the Tunicata, show traces of
it only in the posterior region of the body, AmpMoxus being
the only form in which it is at all well marked. Limbs
do not occur in any members of the grouj), nor are there auv
special jaws or organs of mastication. All tlie members '" ''^^ ^l'-'"-
tion with the eeto^lerm and Z, '^ "f '■'""""" '" """"ec
m the collar region '' P""""""' P"""" i» situated
'• Order Pterobranchia.
(^pMCl'lClttl oocJZ.TT"' ^''^r^'^^ra and
"f Norway, while the latte^wL obLl A' "^ ^^'""' °"' ""^ '"""*
Expedition in the Straits ofTaget: ' ""^ " ^'"'"'^"«-- "
'""*^""^"^'l)--,oniaH„rn.. consisting or a
stolonhko systoni „f tubes ru„„-f •
»'"ues, etc., and Kiving ff ^0,^ Y? 'T "'" "'"•'»-"> "f
»lich c„„t„i„„ .'^. ; t'. . . "'""'"'• 'atorul tubes e„,.l, „,,_ J
-l..tmlike material and fonn 'a " hou 'r-7 ,'"" ~"'1"'»«' "f
" '"' "'f <">l"i'y. and
598
m VERTEBRA TE MORPHOLOG Y.
are traversed, except towards the extremities of the latorul
tubes where the iudividuals occur, by a chitinous rod which
results from the chitinization of what was ouce the stem of the
various polyps. Each of these J- stalked (Fig. 272), the stalk
(C) becoming continuous below with the chitinous rod, and
Fio. 273.— iNDlvlDtTAl, OF Rhnhdopleura (slightly modlfled after Lankkster).
(N.B.— Tlie teiitiicles of oue side of oue arm oiil^'^ are represented.)
B = iiiial piipilla. G = tentacle.
C = stalk. Oa = arm.
Z> = epistomc. / = intestine.
E= trunk region. K = sensory papilla.
F = collar region. JV = notoeliord.
each consists of three well-marked regions. What may ho
termed the anterior portion of the body is formed by a hii>,'e
disklikc iipistome (/>), beneath which on the ventral surface is
TYPE PROTOCUORDATA.
("rr,; ^^^^-r r-' '-^ -"- --
processes (ft,), each carry L,r^,"''^'""' '"» '""S •■'™'ike
( O) arranged pinuately 'T^t "d ' "" °' "I""'"' '-'"«>-
(^;), from the posterior and vL .1 T" '" "'" "''"""■"' ^"<'
arises, while dorsally Ind alrt i'";""" °' """'' "» ^''"'^
(li). at the extremity of which , '""™' " "°'" P"?'"''
'I'l.o ,i; 1- . "I'lcu tile anus opens
Jl'e digestive tract consists of , <,t. ■ T .
"■■"."g the collar, and liavkr,o, r*' "'«'" «sopLagns trav.
-"•face a short b i„d , re"s ^l 1 '""'■ " "" "'« 'l''''™'
with that of the ceso, 1 Zs T "''.'"'!, "''" '3' communicates
cl'ord. The «sopha ~ns fnto f /'^ """'"-taiy ii„to.
fromthelowerendof wliiXh.,? r^'^" ""''"«' "'"'"ach,
i-K "Pou itself, runs frrwlrd, '" "' ^'} ""'''• "■"'• ''-<'•
, The nervous syst m co'dst T: tr ' " ™"' '^»P'"-
'lerm on the dor.al surface of ,t M "'"='^'""■'8 "' «'« ecto.
found a small ciliated eWtiLlrT" "'"^T' ''''"'' '" ■•''-
-> other special se.ise-oi™':" 'cc u^'T" 'r "^r^'^'''
collar a pore occurs which hv » ,"'""='' ^"^o "I the
p.- torates the wall of the bodv , [, '"'""^'' """' '"'"d'
i" commiinication wi h tie e tSri " "'"'r "' ""' <=""-
.•epresentingaiie«retory„r,4n Z' 1 ""^ '"' ''"«"'''='' ■■«
slits have yet been observed ^° 'I"«""™-P°'-e or branchial
".e house is gelutin uT'ntut "^""'V" t>eing colonial, but
»l'ort stalk do not eni'ain ' ' '":■'■" '^'"''' '"'"'"' ''■""' "'e
early separate from Z pa"r"E 1'" "i"' ^"'' ""-■• ''"'
xists of three regions-al ^1^ ''"'•''' <^'«- 273) con.
a large epist,,,ne^ a idX CO 1 ,7™'"''"\P"'''"" '^''i"'' f^^
-c ; the body-cavity b in," i ; ,!*^'™l'''': " P"^'""™ "■"ceral
-«iouB. Two epistle ;o^er:;te ", 7"-'>"-'-«
tl.e c»lom to them passii g tl ro ,g 't ^T:?"' ''"'""« '■""'
awvons system („). The dnr»! '"""'' I""'' "' tli«
i» thickened to f ,rm t e ceZ „" "" "' "" """'"• ••««'""
»i'le of this is a cluster of kLr'T'%"'''''"' "'"' "" <«"^1'
l'"'Wike dilatation a, ,1 Larii' , " "'' 'f' '""""« '" -
•'"■angediii two rows. At m" ^^."""^""M'"--'" 1'""".Ich
At tlie aides the coll
-'<- an ,1 pairoi luternl folds whi
ar iM iv.i.f.'
•luuOU
'•"itorior portiou of the
li slightly overlap the
VLsceral sac and for.n the operJ^Z.
600
IXVERTEBRATE MORPllOLOG Y.
A
I i
w
\ I
upon the inner surface of wliicli there is on each side a colhir-
pore.
The mouth (m) opens beneath the epistome into an esoph-
agus, which iu the collar region bears a dorsal cliverticuluin,
the notochord {x), projecting forwards into the epistome, In
this same region !^'ere is on each side a branchial slit {sp),
structures v !.;.!■ 're apparently wanting in lihahdopleura.
Behind the a „u,gus opens into a saclike stomach from
Fio. 373.— DiAGUAMMATic LoNoiTruiNAT- Srctton TiniouGH Cephalodiscus
(after Ehi.eks from Kokschelt mikI Heideh).
a = anus. n = nervous system.
ex = excretory organ. sp = branoliial slit.
g = ovnr3\ t = tentacles.
m = mouth.
X — notochord.
which the intestine, bending upon itself, passes forwards to
open (a) upon the dorsal surface of the visceral sac, a shuit
distance behind the collar.
The collar-))ores probably serve as excretory organs, ami
it has been stated that the epistome-pores open into well-
developed tubes (ex) terminating in the epistome cavity in a
dilatation ; they also have been regarded as excretory. The
reproductive organs {(/) are paired sacs, which c^peu on the
dorsal surface just in front of the anus. No circulatory system
ide a collar-
601
TYPE PltOTOCUoUDATA.
-"tailed i. the order. '"^^^^^^'-^^ -^ -tLer of the l^
: Cepliolodhi'M
^, ^- ^"'^^" Enteropneusta.
xlie o)'der T^nf
'" »tn,c-ture over iL Pterob.r i ! " "'«<''''<«' ^'Iva-u-e
'>•-« M ami the au„s t«-„,i„af Til "'f ■'"''"« l'"'clical]y
'".a.'c,,ra ,■
«1 surface of wl.i,-!, is a „ 1 , ""'■'■""■ '"''^' '>l".u H,e ,]„;
«- p.'"bo...i..„,„.„„ ,-: '„ :;X';;-".v t.o) „,,el, ,„a ',
»'".'« "l'»" it« ventral .surfa e i^ ""' !""' *''« -'''«io,,
■■-«;<;.., i.s the „,o„tl,. "' '""' "^'^'^ " J'-i-^s the second
J^ije second remo,, ic, „
'■""-■(«), it. post;;;:. „,z'br "■'."'""■' ='■"' f-"- «-
■■«o..t distance in the fo T^Zl"''^'' ''-"-«!« i".'
;"" "'« «i-l- "t the «nterio ,;:,:"■''?. ""^''- ""-■ -alls
«>;Iy a space ,vhich connn ,„':'"' ,''f .";'■'' I«"«™ "f the
I le„oran,Iislnown„s the ',!■ T. I""' "-'.V «ith the
«.on of the bo.Ij. is „„.eh hthan ■/;""'"'"'■ "■■ """k
: «""••"■ ■■"Kions, and contains H """"' "'» l'"'l'o»<-is
'''««st.ve tract and the re t , r *'"'""""' l"""'"" "f the
;:""■ '»' fattened and e::;'::"«r\ ^■""'"'b' it i
"Ise, on either side of ,vh ..hll tn , ''" ''"'•''''' ^'-'face a
;: '!;!'v-ve tra:!:!:i;-:;;:r^^^^^
iiicr
lienor
■ea.se
ones
I1I "'' ^'"'" »' "'«
bIIt?^' cavity eo.a,,,utCL„ w;;*: tT.'r" " "■"- »
I^O'sal to the uot,«h„rd lies »"'""' ™«l'''»Kus.
;' fo>r' "'• '" «o,„e oases many " ' t? ' ," '"" ^'"^ e„„taimus
l«««B.vesie]e, as it has bee fe™ J"' "'"'""""• '^'''" l»o-
>"'tion of the prob,,scis-c„lor V ;vT'''''''m ''''^''■"''■■--■'t a
"o separate cavities, oril ' , ^ ^'" '' "■""''' '!«'" consist of
«comes very iar«e aid i' fe'f "'"' '^"- ""e of which
«-««. while the other rem-^Z ^ . ' ''"'■""" "^ "'e I^'o-
I'e^e structures are a mZ ;<,?'"!/""'"• S»"ouu<{iug
ajersof the proboscis-cJ™ ("y"."'' "^ ""^ BUauch.it
b'^e m the folds, while tl^Tel Is i' ■'" "^ •''""''■vessels
"'"tarn yellow ,„.,„„,^^ , l"\!r""« "'"» frequently
Sianules indicate a Klaudul!, f . '^"Pl'osed that these
*'<"ently the entire'la'^i'fi™:^ ""' "" '"'''''■ "" "
''"scis-ghmd. '°''''' ''"^ I'eeu teriued the pro-
The coilomio cavities of *l, i,
"■""''• ••»« umch siu rr al '''"'"' ^^'«- ^^S, 7/ cop) and
"«'" and left sides bS^ se L!"ed'fr"''' "f """'^^ °^
-J ventral mesenteries." iC tt ' " 7°'' ""'-• ''J-'Io-sal
"■•» end of the trunlc-cceh ,„ „" ' '?"' '^"'■«'"' "' the an.
•»'•<' '"to the collar. ]yin,, '" '"V "'""«""°™ extend for-
---1 a„,I ,„„„i„^, t « petil™,, d "■ ' "' ""^ '•™-'" '''ool.
;;'■■<;'' are longitudinal ,,„ Ifih """t^" '" ,"■« '"'-ior of
"";■'' I'^'l^Kation of the tr„uk„lll , T •"''"■ ^'""'-- '''■-
--"-'-..ophagus, fort-^r ;5;:-^^^^^^^^
'""ar and trunk of a dorsa ''"'"'' <=°"«i»tHig in the
!■"■ '>i«tin.t n,u.eui:r ™ , ' H ., T'!"'"' . '™Si'-Ii"al ves
P'<"" the dorsal vessel bm ch'e ^"'^' '" "'" ""■"enteries
;'•»« of the branchial s i s T, d 1!,""' ',"'' '™«"'^'"'- I'«-
"vard into the proho,,,:' "t" ^r ","" '" ™""''-J
'----^ - t^e "otochor^rir ^^-n,-,J-
604
IN VERTEBRA TE MORPHOLOG Y.
t
The bloocl-spiices iu the proLoscis-ghmd commuuicate with
the heart, aud the dorsal aud ventral vessels of the collar uinl
truuk are imited by a double set of tine lacunar capillaries,
one set being situated in the body-wall, and the other in the
cop — colliii-cceloin. '
(j — tongue- bill- of skeleton.
]i = lieurt.
Jal = bnuicliial valve.
kh - bnuichii.l portion of oesophagus.
ks — bnaichial septum.
kp = branchial porv.
Im — loiigiiudiuul umst'les.
nc = uotoeliord.
nd = dorsal nerve.
no = ventral nerve.
0 = a-sojiiiagus,
pc = pioboscis-coeloui.
pfl — proboscis-gland.
ps = proboscis-vesicle.
wall of the intestine. The blood is a colorless coagulable
fluid, apparently destitute of corpuscles.
In the posterior portioJi of the proboscis is found a plate
of chitiuliko material produced into two horns posteriorly,
and frequently somewhat hollowed out in front. It is evi-
dently supportive in luiietioii, and forniK the proboscis-skele-
ton. In connection with tlie branchial slits a similar chitiiioiis
skeleton is formed (Fig. 276) consisting of a series of tiiii
verse bars placed cn'er each septum between adjacent slits
From the middle of each bar a rod (really double) passi
down each septum (.sA), ixJuI from the extremities a bar (//
passes into each of the adjacent tonguelike calves, each valv.
thus possessing a ))ar from the arch lying in front of it ;;ii'
another from that lying behind it. The septal bars ami ti
is-l
TYPE PliOTOClIORDATA.
tlie bruiichin! slits. ^^^"'^ ^^'^"'^^ tl^^ valves of
;'"'-'":.-ate«t,„e (Fi,, 275, /•
«) auJ eventually opening t„
■■'»rfy i" soa,e species the wall A^ 'i""';.^'^^''- ^^f'"''' I'"«'«-
';;*o »ac„„lati„a, .Lie,, have , e ' f',"" '^ ''"""'""' "»'
""»'"« m the ,„id.lle of the liv' '''?•'•""'''»""'' «•«".•»,
'"ee of the i„te.,ti„e i„ the for. f /",'"," *''""' ""^ ''"'■'"'1 »"■■
.'■""■'3'. "Pe,« a«ai„ i„t , t ie « , ," '"^' "'-". '"-- p.«te.
-i.testi„e of eertai,, A„„eli, f v ' '""''"" "'" "ccessory
'"■' i» P«,„har ei„, „i .r''''-'?;^'"- ""'' Echiuo.Ier„,s
«'«. «ter.„r have hee„ fo,„„ ,,•""'"""'"'" ""1'
«"™.» at present „.li„v„ "' ""'■*'"■•«• "'«■• «i«uifl.
'"' '■l<'"8atVd''errriv!Crrt!,e''n,n' i' '"?"" '" "'« f<""' "f
l-.^ion. with the eel..,,;,,: o , ' h iT"' "™ "' "'^ »"-"'
' " "* '" oouuectiou at
■'' ^ syiiiipiicula.
tb = toiio-uf Ijjir.
t\
606
INVERTEBRATE MORPHOLOGY.
either end, though free throughout the greater portion of its
length. It contains in young forms a central lumen, which
may be represented in adults by a series of separated cavities
and which results from its formation as an invagination of the
ectoderm. From this dorsal cord a plexus of nerve-fibres
extends all over the surface of the body, lying in the lower
layers of the ectoderm and being at certain regions specially
developed so as to form nervelike thickenings. One of these
surrounds the dorsal and lateral surfaces of the base of the
proboscis, being perforated by the proboscis-pore ; another
occurs at the posterior edge of the collar; M'hile two others
occur in the trunk region, one in the dorsal (Fig. 275, B, ml)
and the other (wv) in the ventral mid-line, extending the entire
length of the trunk. No sj^ecial optic, olfactory, or auditory
organs seem to be developed.
The short canal opening by the proboscis-pore has been
regarded as excretory, but the assignment of such a function
to it seems questionable. A similar function has been as-
signed to two short tubes with folded ciliated walls Avhich
communicate internally with the ccelom of the collar, and
open to the exterior by the collar-pores, situated, one on each
side, on the edges of the atrial folds. More definite informa-
tion is required concerning these organs before they ciiu
finally be accepted as excretory ; they evidently correspond
to the collar-pores of the Pterobrauchia.
All the known species of Ualanoglossus are bisexual, the
reproductive organs, ovaries or testes, consisting of simple or
branched pouches situated in the trunk, beginning in the
braucial region and extending some distance backwartls.
Each pouch opens to the exterior by a special duct, upon the
dorso-lateral portions of the body.
Development of the Enter opnezista. — Some species of Bahnio-
glossus (B. Koivaleii'sldi) develop directly without the iiitti-
vention of a larval stage in the life-historj', but the majority
possess a characteristic free-swimming larva known as the
Tornai'ia (Fig. 277). It is a barrel-shaped organisnj, buli^eil
out slightly at either pole, and possessing a locomotor iijipa-
ratus in the form of somewhat complicated bands of ciiii.
One of these surrounds the posterior portion of the bu(l\ ;i^
TYPE PltOTOCUOItDATA. q^^
<'4^ex of the body in an ectocler- '' ""Z''''' "* "^«
;;;f f/f^^^i^^^ the apical plate
(«)> which bears two ejes
Tlie moutJi (J/) opens by a
s ^ort oesophagus into a capacious ,
«ton.ach iS)^ separated by a per! ''
forated partition from the short
rectum (i?), which opens by the
terminal anus. In the anterior
portion o the body is a saclike
siucture(;,c), united to the apical
Piate by a muscular band and
opening to the exterior by a pore --^-^
O') situated a little to the left of ^^«- /^^-Tokkakia Lakv. o.
tiie mid-dorsal line. Thivj «n • -^«^«"»^^o.wm«.
« = apical pliiie.
cc = coilar-cffilom.
^= month.
P = dorsal pore.
Pc ~ piobobcis-coelom.
li = reciiim.
^ = slomncli.
ic = triiiik-ca^Jo^
t ie mid-dorsal line. This sac is
the proboscis-ccelom, and the pore
the proboscis-pore, and in connec-
t on w,th th ,,^^ .^ ^ ^^^^^^^
the so-called heart, which becomes
the proboscis-vesicle of the adult
At a ater stage of development - = .n..,k.ea^,o„
t^vo other pairs of ccelomic sacs (cc and tc^ i T'
pearance at the sides of fl.n . ^ f ^ "'''^^'^ their an-
coHar and trunk c^:' '^Z ""IZlf '"' ''"' ''^^ '^ ^ '^
^-adual transformation of this h v. T '\ '''^"""'^^ '^^ ^^'^
^netamorphosis. ''''^'^' *'^^^'^ ^^ing no sudden
T^>^ Affinities of the Hemichordatn ri
'>"t that tho Pterobnu.chi. ::, te - 7 '''^^
-;nanysi„nhu,,„a at the same til ptu ::"::?: "" f''^^^^^ ^•'^'^^^-^'
- h grcps. Thus, to mention or.ly some i; tl "'"' '""' ^"""^^ "^
'>•> " Krou.^s possess a notochorcl of "mil' "'"''' ''''^''^ '^^''^^'^^^
eollar-pores and branchial slits and r -. ? ■"''''' '^''^'^^^^-i^-pores
;'"■- .stn-ctlv.con.parable re^^ion Th « I "•',*';"' "^^'""' ^''-"-^ i"t(^
608
IN VEIl TEBRA TE MOliPHOLOG Y.
be postponed for the present, and attention called to the sugj^estivc ehar-
acterof the I'urnaria. Its first describer took it for an Ecliinoderni larva,
and tiie majority of succeeding antiiors have been inclined to regard it as
indicating aiiinities with that group. Tlie arrangement of tlie pneoral and
postoral ciliated bands, and the occurrence of the proboscis-pore, suggest
the Ecliinoderni larva witliont doubt, but it must still })e regarded as a
decidedly open (picstion whellier or not these fcatur'-s indicate an alliiiiiy.
Furliier inforauition is recjuii'ed both in regard to the ancestry of ilic
Echinoderms and as to tlie life-histories of the I'lcrolinmchia, before llu^
question can be settled.
Anollier line of ancestry niu.st also be mentioned, namely, one wliicli
leads back to ancestors common to tiie Ilemichordates and the Prosopygia.
The similarities of the Fterobrancliia to the I'olyzoa are striking, ilici'C!
being the same bending of the intestine, similar lophophorelike tentacular
structures, ami, what is of considerable importance, a dor.sally situated
nervous sy.stem arising as an invagination of the ectoderm. A furihn'
point perhaps of some imiKirtaiice may also be mentioned, i.e., (he occur-
rence of three :>ectioiis in the body-cavity of the Brachiopoda. In following
out the line of difscent suggested by these similarities, we are, howevci',
quickly brouglit to a halt by the uncertainty connected witii the origin nf
the Prosopygia. and we ai'c left standing Ix^twecn two lines, one leading
back to till! Prosoiiygia and the other to tins Echinoderms. Whether or not
the.so two lines conv(n'ged to common ancestors in pre-Cambrian timo can-
not be ascertained, and the solution of the problem must be left to fuliue
eml)ryi)logical investigations.
11. Cl.vss Cephalochorda.
The class Cephaloclioi'dii oontaiiis a single body on the; left side id' tin'
cauihil tin is situated the anal optnung (Fig. 278, hi-
1 lial»it;it,
suiid, flic
0.
11(1 SdllH'-
tlie iiiid-
oilv w.ill,
[.'till i'»l.^
. Vn^U:
niil.il I'm
till' \(ii-
itll tiM'-^<'
-
U' .il til-
TYPE PItOTOCUOlWATA. gQ^
(4J. The oltVwa ). f tli^': ".r""^' '^'■"'"' "'« ""■"-
.Mes of the boa;'t .1 "" e ''e", ■^^.r fl, '"'t • l"' "'^
crea.„,K i. «,e, f„«e t„«ether beW ete ':; t \ '"^
l».-e thus e.ch,«i,.g the utrial c.vit/a, .'^w ,,,;;, n"-''
hue,l thr.,„(.ho„t by ectoderm aud sur ■om.d; 'l '?
veutiHl surface of the auterior two thirds '■" '^ "'"'
liorly the cavity is ch,spd l,v .1 V , "" ^'"''^'- '^"'«-
rt« r: eye "* = "•"'*'c.|,lni,Iiun..
ch = n,.t„d.or,|. '^ "^ ""•""'•
i' = rc-producdvc. organ. i> - "inal pore.
/ = liver. ''"'■'•''' '"''vc'-conl.
«i' - biniicliial cltft.
torn of which Ii.» th. oriKii.al n.onth, th a.-ins „f th„ l,n ,
i'niso.Iint,,nuMUM-onss.n.so,vpa,;ilIa>. ' "^'■^"^**
T iie cctodenu is vcrv simnio in ;♦ , i
««;;.;^ i..r of c„n.;c:;:,i^;;;,:r; ::•::;;— ^^^^^
;:":r::^b;::;:';;:r:;:;:r""'''r^^'"-^
-'■■"^''"M.Had.vc;,i,c.i::t:::t:;;:i.:^::;;::;r-;'-;:--;:
610
INVERTEBRA TE M0RPH0L06 T.
time these folds are gradually constricted off from the intes-
tine, and at the same time are divided transversely into a
number of sacs lying one behind the other, their number in-
creasing as the folds are separated from before backwards
from the intestine, until in A. lanceolatm there may be as
many as sixty-one. TLese sacs are the primitive mesodermic
somites, and the cavities they contain are the primitive ca»-
lomic cavities. At first entirely dorsal in position, the various
sacs later on extend ventrally, those of opposite sides meeting
below the intestine ; and still later the cavities of these ven-
tral extensions fuse to form a continuous cuelom extending the
entire length of the body on the ventral surface, and forming
what is termetl the splanchuoccel. This becomes eventually
separated by a layer of connective tissue from the more dor-
sal portions of the somites, which remain distinct from each
other throughout life and are termed the myocoels. The future
history of the two portions of the mesoderm thus formed
is very different. The walls of the si)lanchnocc)el remain
thin, and the cavity well marked (Fig. 279, co), but in tlit*
myoccels the cells forming the median walls become converted
into longitudinal muscle-tibres {m) which traverse the entire
length of each myocoel, filling it almost completely, and are
inserted into plates of connective tissue which develop be-
tween the various mjoceels and separate them from one an-
other. At the same time each mjocad becomes bent, so that
its dorsal portion is directed downwards ami forwards ami
its ventral portion downwards and backwards, each muscle-
plate having in a longitudinal s(!ction of tlie body a <-shiipL'd
appearance and fitting into the one in front of it. AViien
the epipleural fohls develop, both the s})lanchnoc(t'l ami
the muscle-plates are continued into them, the muscle-])lat{'s
lying to the outer side of the sphinchnociel, and their tihrcs
here having for the most part a transverse direction, in-
stead of a longitudinal one, as in their upper portions.
Owing to the myociels being practically obliterated h\ tlif
miiscie-])lates, the (-(elom of the adult is j)rincii)ally formcil
of the splanchnoc(t'l, but other spaces also occur which an;
]n'()ljably schizocd'lic in origin and form various lacnuM'
throuL'hout the body.
a
b
c
CO :
e :
TYPE PIWTOCHOBDATA,
611
ia wLich floM numerous coTn.T ""'"'""'I'S » ""'"'ess blood
Byseem eo.»i.ts o r 11, rH""''? ""P"-'-- The
.-. po..o„ o. u. oo„:::Lnjs,a r £r -
l^IG, 279.— TnAN8VEH8E SppTrnw m„^
•lesccndhiff aoi-hi ^' '"" "«"twio).
« = (lesct'tiding aorta.
* = atrial clmiiiher.
c = riotochord.
oo n co'lorn.
« = liyp<)l)n»Khfnl groove beneath
wliich is the n.scci.ding aorta.
9 — reproductive orgim
kb = branchial arches
^ ~ pharynx.
I = liver,
w = Miiisrlca.
n = nepliridiiim,
r = nerve-cord.
*» = nerves.
li.e bmudnul resiou „f tl,e intestine It ,.,,,1. „ff i
va.-.o„s reKious „f the h„,ly whid, ,*,!!'""'''"''"
f^'I.ilhu-ies, unite ,.„„in to fi,! ,l '"■""'<'"K up into
V"i". which, „u»si„; „ :.,I '«""•""-.'-. ■■ vonfal
«."uehi,;r.--:/r^!e'i^r:L":s^:r:::!:
612
INVERTEBRATE MORPHOLOGY.
W
sally to unite witli the right aortic vessel. The blootl which
passes from the dorsal aorta to the iutestiue is not, howevei-,
returued directly to the ventral vein, but the intestinal capil-
laries unite to form a vena porta which passes to the liver
and there breaks up into a second set of capillaries, these
finally emptying through the hepatic vein into the ventral
vessel. An hepatic portal system, resembling that found in the
Yertebrata, thus occurs in Amphioxm. While passing be-
neath the branchial region of the intestine the ventral vein
gives off paired vessels, the branchial arteries, opposite each
branchial septum, and these passing dorsalwards in the sep-
tum open into the dorsal aortic trunks. There is no definite
heart, but certain of the vessels, notably the vena porta and
branchial arteries, seem to be contractile.
The notochord (Figs. 278, ch, and 279, c) has a much more
extensive development than in the Hemichorda, since it
traverses the entire length of the body. It arises from the
dorsal surface of the digestive tract, but early loses all con-
nection with the intestine ; and though in early stages it con-
tains traces of a lumen, this cpiickly disappears, the cells
becoming richly vacuolated, so that the notochordal tissue
assumes a characteristic appearance. At either end it is
pointed, and throughout its entire length it is surrounded by
a sheath of dense connective tissue, which is continuous
below with the partitions separating the splanchnoctel from
the muscle-plates and these from one another. From each
side of the dorsal surface of the sheath a longitudinal lamella
extends dorsally, the two lamelhe enclosing the central
nervous system and being continued above it as a strong
neural ridge (Fig. 27',)).
As has been already stated, the adult month is formed by
the margins of the oral hood, the original larval mouth lyini;
at the bottom of the f)ral cavity enclosed by the hood and
beiu'f surrounded by a (drcular fold of tissue termed tho
velum. A short tube leads from the mouth to the branchial
or pharyr.geal region of the digestive tract, whose walls me
here perforated by numerous slits (Fig. 278. up) ])lacing its
<«avitv in conuiiuiucation with the atrium (see Fig, 270). In
the adult the slits are elongated ami are i)lac»nl (iblicjuely to
TYPE PliOTOCIIOHDATA.
613
the brauchial re^.ion of IITZT ' "^"^^'^eplates of
tious between each pair of slits ,;^"^^^^"'^^^' ^^^ ^Jie parti-
tl^e same side of tlxe body skeletal
|■ «tu,n..s of d..v,.|o,HM,. :. ; i" ""■; '" ""• "■"-'•-Pl.-.t.s. In
■••'-I>"'Hl .m.ta,,u.rin.ll \ ^ , " "''^''^■^ '"•*' ''"-'"i-'i "Lich do
^--•<' H^ <'.o ...no , s. J *;;;;; "" "''""' '"'"^ -••■ •-'-!
,„ , "K'ifimon.! coiT(.spoii,i,.,,e,« is lost.
Fin. 280.-nrAo„AM ok tiir
BiiANdriAi, Wkki.kton of
^»ip^'ioxilS (after Si-KvaEL).
* -«Vniipliculii.
«* - sf|t;,il bar.
<6 = tongue bur.
ive
ciliate
tlirou
i»Joo(J-vesselH occm- l.,>fi. ; n
into ti,.; ■■;■,"*""''■>■ "'•"■"">'iM««»e8
614
IN VERTEBRA TE MOliPUOLOQ Y.
exterior by the atrial pore. Along the dorsal and ventral
mid-lines of the branchial region is a distinct ciliated groove,
the ventral one having projecting from its floor a longitudinal
ridge, while ventral to it is a chitinous skeletal plate composed
of paired moieties having a metameric arrangement. This
ventral or hypopharyngeal groove (Fig. 279. e) is termed the
endostyle, and from its anterior end a band of ciliated cells
passes dorsally on each lateral wall of the pharynx to unite
dorsally with the epithelium of the dorsal or hyperpharyngeal
groove.
From the digestive tract behind the branchial region a
diverticulum, termed the liver (Fig. 278, I) arises, and pro-
jects forwards, covered of course by the body-wall, into the
atrial cavity (Fig. 279, I), and behind this the intestine passes
straight back to open at the anus (Fig. 278, a), situated, as
already indicated, upon the left side of the body, some dis-
tance from the posterior end.
The nervous system consists of a thick-walled tube (Figs.
278, and 279, r) which lies immediately above the notochord
and is enclosed by the connective tissue lamellre which arise
from the notochord-sheath. It extends throughout the entire
length of the body, tapering rather suddenly at either ex-
tremity. Throughout the greater part of its course the lumeu
Fig. 281.— Diagram of the Antekior Portion of the Nervous System
OK Amphioxiia (after Hatschkk).
cA = uotochord. JV = hypophysis.
1, 3, 3 = are placed over the three ventricles.
is very small, forming the central canal from which a well-
marked cleft, the dorsal fissure, extends to the dorsal surface.
At the anterior end of the tube, however, the lumen ealar-os
to form an anterior ventricle (Fig. 281, 1) which has been
compared with the anterior of the three primary vesicles nf
the Vertebrate brain, and behind this the lumen couUucts
rYPS PBOrOCHOHDATA.
VOD9 Stbtesi
615
formiug the aqueduct of Svlvins nf n,= • , i •
belaud this again au expaudon !f fh 1 ^ '"''"" ^^^^ "''"«
do«ul fissure form, a /C T / .'?1 .'''"■"''' I«"«°" of the
the Vertebrate hiuTbrfr the , n" ^'^ '"""" *° "'»' "'
Vertebrate braiu I^TCI :;t':rir,*° "'" ^"'^-•^•"-<'
which is increased bv tl,„ ^ umrked— a resemblance
(^) of the :S ten r e^r^'r ?/ " '""'""-"'''' -'--on
l^od,, where it ZT^^Z^^'^ ''«-' ^f- of the
Jerm. This is tiie rem J,„ nf JeP'-essiou of the ecto-
-itl. t.,e oxter""; rh e,ftsrtT"'"f °'' °' "-^^-'Wele
-verare";:rffrc28i) trrr ''-- "^'^- °'
come from the dors- 1 nm-t; „ , '""' ""°'"' of wldch
1-i.- on each sll " ,, X ™ " '^™"' ^''""^ ""^ "-"J
tl.e dorsal surfa e of e b,'.! n"'?"'' '! " '•"<" ■■"'"■''« '-"'
v-tral side, a condi i :,', J " iT;' r.lfr ' " m""« '"'"• "-
...etamerically-arranged nerv T, ,"' ,'" ' " ^-'eJing
■■ever unite to form a comm™, ... """' ™''"'''' "-oots
'-0 the .^.-inerve:r. :, ;::trb;;t r^tfr*'"'''''^
are sensory iu fauctiou, while he 1 IV^ •"=^'='-"»Iess they
-.W;binK only the mus^lature t^ tCbol""" "" "'°'"^'
I" addition to^hese a;\>: .l'\:''';''''-^'" '•-«»'•
ai. exceedingly simple evl Z ^ ' ""'' '""^ »-ei>rosent
'l.e brain, am/in "^ ' .S^'.f r„,::'r: t -"""""^ ""' "'
;>■■«-, -..-rounding a depr ss „ irS." ''f ^■'' "' -"^
«a„ng l„„g refractive hiirs. Tl, 1 j:''"""''""- ™"»
0 a sense-organ of some kind, but its exlct f !• """'"' '"
ku(nvn. ^ ^^^c* function is ujj.
Differeut stiiicture.s Iuivp fmm r
*lered excretory organ I„ 2 «"! '? """' ''«°" «™-
'•-«".. l.a» been assi'I^^ J'l "^^^ .•"7. - ---tory
of the oral cavity on 'tl.e^ fcft's d '':,' !'" ""^' '" "'" """
siiK, and conimumcating by u
616
INVERTEBliA TE MOliPIIOLOG Y.
fuunel with the coelom just behind the level of the velum.
{Secondly, although iu all probability they are not uephridia,
the "browu cauals" may be here meutioued. These lie in
the sphiuchnocuel at about the level of the twenty-seveutli
muscle-plate in A. lanceolatus, and open by wide funnels into
the atrium, though it is uncertain whether the inner end lying
in the coelom is perforated. Thirdly, iu the pharyngeal
I n s r 11
Fig. 283.— Excuetoky Organ of Amphioxus (after Bovkri).
nc = uephrldium. tip = uephridiiil pore.
nd = nephridial fuiuu'ls. « = synapticiilum.
/ = braucbial septum. //= bniuohial tongue.
region a number of nephridial canals have lately been de-
scribed. They are situated above the upper ends of the
branchial slits (Fig. 282, nc), each opening into the atriuiu
()pi)OHite a tongue-valve {np), and from the short tube whuli
passes inward from this opening an anterior and a posterior
l)ranch arises, each of which opens into the coelomic cavity
by a terminal funnel. Between these two funnels three or
four others may occur (nd), and around the mouth of eiu:h
funnel are a number of threadlike jn-ocesse i which end iu
round strongly-refractive cells. That these structures are
UPDhridia seems indicated by their relations to the cwhm
and furthermore by the fact that iu the neighborhood of eacii
TTn PBOTOCHOBDATA.
of tLem the brancliial blood-vessels fr,,™ „ ,
may be regarded as a glomeru ussuH " "" ' P'"''™ ""«''
t."-vith the uriuary ttbulerol" .rVertlrrtru, " """"^"^
Ampho^,^ is bisexnal. The nmZZt ^^•
or testes (Figs. 278 ami 279, M occH iu the ' °T" '' "''""''
"UJ are arranged metau.o i.,!! / epipleural folds,
Tl.ey lie at the level oi the ^f T ""'■':>'->'i^"' metamere.
=-1 the ventral trins Lt , C! e" ,"' '"'"•"' '""^itudinal
« cceiomic cavity wh • h L lit' ""f 7' """'"'"'d ''"''in
of the segment! o ' • i h tiL'"' 1 "" °"«'''^' "^o^^'^
Tl^ey lie on the inJ^^'t^^T^'^-^Zr ''^
covered ou their iuuer surf-.PP« 1 li !, ^°^'^''' ^^^ a^'e
-i-1^ the rern^oan C ;^^^^^^^^^^
;^to the atriun. and thence 1 iullo I^ " T'""' '^"^"^'
the atrial pore Thpvp ..v *'^^^'"^^^ *« the exterior through
poie. iLeie are no reproductive ducts.
considered the mos;,,n„-uX^^^^ ^'-- -»all> been
•" =^ 'nore or less modified condi on ,p\7 7^^^«"^'"g. ^" other words,
i-e deseended,-and there a em?' "^ :'"/':«'" ^^'^'^'^ the Vertebrata
o~^'ns and the larval L'Mnm-J.rZUTl^'T^^^^^^^
-I'Ported. The character If ::r:f t',! 'f ?"'' ^^ ^'^•^^' ^^^ '-
«V«tem, the arrangement of the ne X nP . , ""'"'^^"'•'^ '"^"^ "^^'vous
If ^tes, the occurrence of an h pit ,o ,. i ', 'T'^ *'" '''''^' "^"^de.
f''« early stages of devel,>pme t 'rf ^ i '''7^'^^'"" '-^"^1 the character of
-Plioable only on the snpp u^. o'a'son "v. . ' "'"""''^^ ^^'^"^'^ «««'"
Ou the otiier hand ni i.,.. . '^o^'e^'Iiat close affinity.
, '- -r.ed. It trlr '™ ^ ; e Enteropneusta ar^ hut slightly
the arrangement of the ^^r..^T^J^J^^'^r ^^""'"•'^'- ^^
<'^'Pen..,,. is nndonhtediv much more 1 . ' ''^ ''^"''"">.'^^»*v"*--
, !''au yy./„.o,//..v.,, ,,Kl both are 1 ; Iv ' "'"' '''^ ^^"'^^'''^■"^•^ ""«
;-- ^'- '"^--'-'''Positions,
Extending through 0 etelt a™ ""'"'""' "*' """^■
'vhich communicate .^1 Ihe Won7"''"7 '^™-'-« tubes
They arise a. outgrowths of the bT r''"'" °^ ""^ """'y-
l.od.y.wall before fhem beii L^ T''"™?^"'^ ""'' P»«>' "ie
ectoderm, beneath wl ch is Tl. .'■' '"""' «"'™''Hy by
each is separated int^ J: cirr^ eT^r""^^ "^^"^' ""^
partition which does not L ' '' ^>' " '""si'u.liual
enlargement with .tier; iThZ', "''"J' '"*" "'« "'»'""-
:--c_.ati:^n^rb\t\-
oppoiiiirbiariiiXHSTatr "'"T -'■-
-- out into two '"^uiar pr„;est:rthe'"c.';i:i'rd':: •::
II
620
INVERTEBRATE MOliPHOLOOT.
siphons, in whose walls circular muscles are developed to
serve as sphincters of the opeuiiigs. T}ie branchial siphon
opens posteriorly into the branchial region of the digestive
Fig. 283.— Figure of a Tunicate, ILterotrema, removed prom the Test
(after Fiedler).
A =• atrial pore. pc = periphiuyugeal ciliated band.
an = auiis. « = stomach.
CG - cerebral ganglion. m = subneural gland.
en — endostyle. »i = branchial stigma.
ex — excretory organs. t = testis.
/ = intestine. iid = vas deferens,
tract, the opening being known as the mouth, and usually
being surrounded by a number of tentacles (Fig. 288) wliich
arch over it. The atrial siphon, on the other hand, does not
open into the body proper but into a cavity, lined probaiily
TYPE PROTOCnORDATA. Qg^
anterior and posterior em TL ' . "•"'' f ' "'" ''""■^■"'^
Ws walls are tenued tl e taufle iT- '^' '" "'" ""■""■' ""-1
atrial o..ityoiA,npMoJXT^:Jll:°7r'"' '" "«
sive developueataml arises ia tie Kvv ■""'■" '*'"'"■
".en> at t,i sa,„e t^L'dl't,; r ,! t":;; t^l" 'r '"''"''^"
become coiitiuuous. ^' ^'''^ ^'^'^^ cavities
The external surface of botJi flm ,» n
proper is covered witl. elde™ tu ret ,"",'' ""^ ''°''^-
layer of mesodermal connective hsuei'T f"'" "'""' *
iibres. The cu,l„,„ic cavity 1,^1 of °7''""*' """"='''-
■spaces which l.ave,e»pecii„;r,t ais'of «'■" '""'""■
'■es-on, a more or less cleiinitei.ra.l;e,, „ ^^^^ . '« """"r'""'
vessels. In a somewhat ,H«t;,„.t *' "' "'"' '^"^ as blood-
t'.e bod, is situated at hi 'tri^ir""' "T, '''"' "'"' "'
of a single layer of cells. Z t^l^" 7"'^. ?'" '""'""'
verted iuto muscle-Hbres Tl,„ . ' ''''"•"'' "'•« «'u-
wavelike, starting f™,„^een^a J '■"'!™' "' '"" ''^•■"■' --
rather .nieUl, to;ards ^21:^^^:^!^'^' 'f""*-"'
« that after a certain number of beafs,'/'™'"""^
contraction-wave be..iu, «„,„„,!' ""''' "^ ^'•''''='' "">
andf„rasimihu.n„i:fratnh;:i™r:j
This change takes place with a certJn f ? "'' '''"'•
and at each change The course o^ til 7 > ;',°""' "' '■''^"""'
at least of the l,ody is reve led 1 7 "■""«'' '■• l"""""
;..'" a large lacnua, one I ' ^ Lh nn f ir'n'"' ''^'"■' ""-»
i"e of the branchial sac, while tl't,'^ '«:;:;'?'' ""''■
branches to the intestine niid t^^t , ^ ^ "" lacunar
line of the same r giorsmalle. C'"' " °"" """ '''"■^''' ■■"''- ■
cl.;al bars, nuitiug ^^the" Zf^^r^^^Z^^" ''-"■
colorless and contains amoeboid oornnscL vK V '"""' '"
usually coloriess, though a few coWed nn ' "'■" '•''""
pl«mentedeeUsofthe^st,are7:°;::!tr;:;;r"''""« '"^
li-e mouth opens into a capacious pharyngealor branchial
622
INVEliTEBRATE MORPHOLOOT.
\
l\
't
sac whose walls are, perforated by numerous slits or pores
termed stigmata (Fig. 283, st), arrauged iu transverse or spiral
rows. The bars separating the stigmata enclose lacuna)
which place the ventral and dorsal branchial lacunre iu com-
munication so that the walls of the sac are richly supplied
with blood, opportunities for its aeration being provided by
currents of water drawn by the cilia which border each stigma
through the mouth and out into the atrial cavity, whence it
escapes by the atrial aperture. The transverse bars which
separate the rows of stigmata are generally stouter than the
longitudinal ones, and iu most species there is a second series
of longitudinal bars lying on the inner surface of the sac, less
numerous than the bars which separate adjacent stigmata,
united with each transverse bar by a short connecting branch,
and bearing opposite each junction a hollow papilla which
projects into the cavity of the branchial sac. Running al()nrauchial cavity ; these are termed the dorsal languets.
The remaining portions of the digestive tract is in i\w
«imi)le Ascidians generally situated iu the mantle on the left
.side of tlie body, owing to the enormous development of the
branchial sac;, but iu other forms it constitutes a part of a
viscv^iid mass lying immediately below the posterior end of
the b"-c. The tt3S(jphagus, l)egiuning at tlie lower end of thii
sac, forms a short tube wliich opens into a fusiform stoma. Ii,
from the further end of which the inte.stiue (/) arises. This
is generally bent twice upon itself, forming thus two loons,
and ends in a straight piece, the rectum, which opens by tho
TYPE PROTOCHORDATA. 623
eutue length of the muer surface of tlie iutestiual wall form
HR the typhlosole, aud a number of brauche.l tubule ' open"
«ud aud giving oir nerves both anteriorly rnjl^f^T''
tbe anterior part of the brancSre ' "tt Lt X" Jet
,^arkod papilla which n=av possibly be .JoILL:^^
rhe gland, from .ts relation to the nervous system and tT^
£:rr"r .:;„i:rr,' rtSif r-ss
orsal languets, and the papilla at the opening of the tl ^
the subneural j, serving as fins. Tjinh
the anteri"umcate
.«-t .e.t.kable ^'^^ ^tJ^ ZIZJTT " ''^
:-:rtL: zt:^s^z :!,;t;r ^-"r
J-Ces of ,vMeh it «e.„« „n .en-l^la . ::.' ^
tube throughont nearly it, entire ieugth, lie, a uotochoil 1
wlwch servex a, a skeletal support to the tail, au o" ii"
«.le of ,t « a plate of lougituib-ual .m.sde-fibres
iiy uioauH of energetic lateral movements of the tail this
arva s,v,,ns about for s,„„e tin,e, but when about to tra'
one';,;;; >;■'" '"'"" " '''"'"■" '- -•- -""io 41 ";
me ol the a,lhes,ve papilla,. The tail with its nervous svT
t"n, n,„scles, a„ tail and
i!h1 tjjut tlie ndiiltH, except in tl
the fi
!lH
■eo-Hwiimning Iwihit
626
INVERTEBRATE MORPHOLOGY.
Several
are persistent, are to be regarded as degenerate,
orders of Tuuicates may be recogoized.
1, Order Larvacea.
To this order belongs the genus Appendictdaria which has
already been several times mentioned. It is throughout life
free-swimming and retains the larval tail, greatly resembling
in general appearance a tadpole larva. It secretes an exten-
sive test which is gelatinous in consistency and is but loosely
attached to the body, being frequently thrown off shortly
after its formation. The body (Fig. 285) is comparatively
f
.Fig. 285.— An Appendicularian, Oikopleura cophocerca (after Fol from
Hrrtwio).
a " unus. /= ciliiited groove.
c = uotocbord. (f = brain with auditory vesicle.
d' = pharyux. g' = first guiigliou of tall,
d" = stoiiwich. /i = testis.
en — eiidoslyle. ov = ovary.
« — brauchial cleft.
«mall, the tail being attached to its ventral surface, while its
posterior extremity is somewhat enlarged and contains th«^
reproductive organs {ov and h). The branchial sac has but a
single pair of stigmata («) which open to the exterior b) a
pair of funnel-like tubes situated behind the anus. This ar-
rangement represents exactly a condition present in the larvio
of other Tunicates, two stigmata lirst forming and the atrial
sac arising as two separate invaginations of the body-wall
J — -A- — — l.r-.l. Al-a. •»*.».*»..»•»» <.iw».v. <^i.« ^^*\r\*% 4-l»/^ 1 tiiraryi 1) < f loTlu rvtilv
Several
rhicli has
;»liout life
isembling
au exteu-
it loosely
tf shortly
jaratively
ter Fol from
esicle.
, while its
itaius tlu^
has but !i
erior b) a
This ar-
the larvio
the atriiil
body-wall
-tions nulv
TYPE PROTOCUORBATA. 627
later fusing to form the extensive atrium. The eudostvle ie.\
(cWipts ht.lo« *i 1 , h'^^h^i'i IJ/ ;• llie uotochord
2. Order Ascidiaceae.
iiiey ditter from the Larvaceje cliipflv ,■„ +i i J°"-^«".
tail iu the acIuU aud iu the at^e d ve/„, l^t oft," ','" "V't
sac aud the m„ue.-„„« stif-matt '"'"'"P""^"' "^ "'« '"''■"^""al
Ow,n„ to the complexities prclueed by the methods of
InuUms .t ,s cstoma.., to divide the o..de/i„to ..boSate
1. Suboriler Aaeiilm simplkes.
Tl,e simple Aseidians agree with the description civeu a,
typ.oal and ,„ not re.p.ire any further notice llr, eSe.t Z
moufou the fact t u.t there are included within t!,.: suIk^'i
innpima. 1 ^ formation of new individ.mls takes „l,„-e i„
these cases from stnlonlike oiitirrowths of the nnl. ,
uud each bnd remains seated upo'n tl " ttln „ 4 1 d',',";
ts own test. The stolon (Fi,,. 28r.) arises fron, the lower 'f
->n of u.e body of the parent and pushes before' it a por i i
628
INVERTEBRATE MORPHOLOGY.
of the test ; the cavity it contains is continuous with the body-
coelom and is therefore lined b}' mesoderm, and is divided
into two compartments by a longitudinal
partition which may be traced back to
its origin from the posterior wall of the
branchial sac of the original individual.
Since ectodermal tissue lies between the
mesoderm and the inner surface of the
test, the stolon contains portions of all
three germ-layers, and a portion of each
jjasses into each bud (b) as it arises.
The first indication of a bud is a slight
wartlike elovatio'i of the wall of the
stolon which increases in size, its cavity
being a diverticulum of the stolon -coelom.
Fig. 286.-PonTioNoPAiuto the elevation a process (en) of ihe
Stolon of ^^'^^p;;-"- gndodermal stolon-partition extends, and,
(after Kowalewsky from _ ^ _ ' '
KoRscHELT and heidbr). forming a hollow saclike body, gives
rise to the digestive tract of the bud.
The various layers give rise to their
respective organs with one exception,
and that is that the atrial walls, the man-
tle, arise from the endodermal branchial sac as diverticula
which unite together, the atrial cavity being thus lined
throughout with endoderm. Such anomalies are not infre-
quent in the Urochorda, and indicate a necessity for further
study of the nature of the germ-laj^ers in these forms.
The simple non-budding forms are quite numerous. Com-
mon genera are J/olgnla, Cynthia in which the test has a
leathery consistency owing to the fibrillar character of the
matrix, and Boltenia, a stalked form.
b = bud.
ir — braiicli of stolon.
ec — ectiiderin.
en = eudodeiiu.
2. Suborder Ascidim composite.
All the members of thi?- order re])roduce by budding iu
.some form or other, and «liffer from such forms as ClanelUna
in that all the individu.-' ii remain imbedded in a common tost
whether or not they rem.!i5) in organic connection with (uie
another. The gmup seemn 'a lie a ^omewlsat composite one,
^V
the body-
is divided
ugitudiiial
il back to
all of the
udividual.
tweeu the
ice of the
ins of all
n of each
it arises.
$ a slight
11 of the
its cavity
on-coelom.
en) of the
ends, and,
dy, gives
the bud.
1 to their
exception,
, the muii-
liverticula
iius liued
not iufre-
jr further
IS.
us. Corn-
iest has Ji
iter of the
uddiiig iu
Clanellhia
lumoii tost
1 with one
30site one,
TYPE PUOTOCliORDATA. ggg
aud it is probablp Hiaf ;* ;
possessing a short »tol„a eLet ,„.! ^''Y"^' *■"' *'^''"'Pl«.
former geuus, from which b X ^ ^ "'."^'f '" """ "' ti"*
separate fro. the ^^^ ::^^^-!^~ ^^
^-.^ox geuus, trom which bnrla « • , • 7 **" °^ '^e
«efro. the -oJL''u t.T iSj^H^ ^
OK THK TEST (a..e. Kow...wskv .C Kohs hI.'? r'""""' ""^ «"«^^^^
« = parent iudividu«il h ,** . , '*'"' «•=">«•»).
* = *^"'on
a„d so the oo.on;'.:r„drr ieTtrrs;:j'';:;;,£rr'''*'
connect on with thp nrimnai „i«„„ u "'«»wuuais tailing to form a
colon,, stni, horvLrSdedrih^Zlotr '" " "" "'^"""«
3. Suborder PyrosomidcB.
the central cavity or cloaca into whid the! it, f ?"
open, the br.ancltial apertures opening on ILelwT"
cylinder. Each individual 'resembles in ,!;.^ , "' ""*
Ascidian, the principal differ cebehrthatt'llr"'^'''
ture, as in Botryllu., is at the posteri™ end of t L bo "''"';
tl.at each individual has the poler of repto ,:i gl^ddW
parent .o.ms uot, uowever, degenerating after giving rise to.
682
INVERTEBRATE MORPUOLOOT.
buds, as iu Botryllus. The buds arise from the branchial
saos behind the eudostyle, and, on separating from the parents,
piyce tJiemselves oetween them and the opening of the com-
moii cloaca, so that the okiest members of the colony lie at
the closed end of the cyli. ler. On each side of the branchial
sac of each individual near the anterior end, or more precisely
near the peripharyngeal ciliated bands, is a mass of cells
which are brv.^l'fly phosiihorescent, the entire colony, which
may reach a length of over a metre, emitting a brilliant light
when stimulated.
The development of Pi/rosoma is exceedingly interesting
inasmuch as it presents an alternation of generations. From
A B
Fig. 289.— Lakval Budding of Pyrosoma. A, embryo divided into the
cyatl'ozooid aud four iiscidiozooids; B, Inter stage shovviug the asciuiozo-
olds twisting to form the circle of four primary individuals (after Kowa-
LEWSKY).
cl = cloaca. en = endostyle.
el = elseoblast. /* = heart.
n — nerve ganglion of ascidiozooid.
the embryo which develops from the egg at a very early
stage a stolon develops (Fig. 2d9), containing a prolongation
of what corresponds to the embryonic branchial sac and aiso
•of the embryonic mesoderm. The embryo itself nevei'
reaches a full development and is termed the Cyathozooid,
serving to supply the individuals developed from the stolon
with nourishment until they have reached a certain stage of
development. This it is able to do on account of the ovniii
being plentifully supplied with yolk, which the Cyathozooid
gradually absorbs. The stolon at an early staf^e divides iuU^
TYPE PROTOCHORDATA. 633
in a commou test ami ,1. f ^' ^^ ^-^'o^ed with it
end of the cvliiulnVnl ..r^i^, a ''"*-" occupy the closed
.ooia cie«e:^!;t": a°s,/: "2t r r' ""'"^"'""-
cloacal cavity of the coin,, 7,2 ."°™P''' ^'^ 'lisappears, tlie
p.-es.io„ of t'he tet :t;~re;;;af d 7""' ''' ' "«-
imlividuals arise by budding ^ ""^ '''''''^'' "' ""^*-
the first generation of Botrmus Sids wl ^^.^"'"^''^'d' ^'l"«h represents
and that it alone degenerates the P^^^^^^^^^^^^^^ '" -^ embryonie eondition,
listing and forming LrtsTfthffnir , «»««««d,ng generations per-
zooid there oeeurs bd nd ^e br h: 7^ ^^''^ ''^'"^- '" "^^^'^ ^^^i^io-
cells termed the 2^ Fil' 'rrlHr"'';' ^""''^^ '"''^^^^^ ^'
tl^ough it has been ^J^^^ii^^Z^^^ '^ ----''^i".
larval tail. •' •' represent the rudimentary
3. Order Thaliacea.
The Thaliacea are with a siugle excenfmn r.oi •
isms, and present a lifo-histo../„o2 e'aW C X °'"'"'-
rence of an alternation of Keneratiors T„ , ^ °r'"'"
(Fig. 290) a well-developed t"t is pi.enfa'dr''" ^"t"
ture of the mantle is arranged in bands wl.t.. "f™ '"
surround the body and fuHher^l'thoVltndtn S
together on the dorsal surface of tlm 1.^ V '^^^'e^cj to unite
posterior end of the bodv %!« . ^ , ''*"^*'^ ''^^ *^^
- grouped toJIher^oL^^tr^n^
(-) lying behind the branchial sac anrveZll T""f "
some forms the intestine is more elonrted nnd ^ ' T^ '^
Avhat from the nuclen. Tl.. ^^°"8ated and projects some-
■rm and positzon ; U i,as m connection with it three pigmented
634
INVERTEBRATE MORPHOLOGY.
A
\-
spots probably represeiitiug eyes, and the subneural gland is
present as usual.
Each species of Salpa, however, presents two distinct
forms {A and J5), differing in shape and in the number of the
muscle-bands which are found in the mantle and having like-
wise a different origin. In the sexual form (A) reproductive
organs are developed, the ovary usually containing but a
em
ma
Fig. 290.—^, Salpa mucronata, the sexttal Potim, and B, Salpa demoera-
tica, THE Non-Sexual Form of Salpa democratica-mitcronata (after Claus).
c, cl = cloaca. ni = brauchial pore (mouth).
cp — ciliated pit. ma = test.
em = embryo. n = nerve-gauglion.
en = eudostyle. nu — uucleiis,
h — heart. si = stolon.
single ovum. This when fertilized (em) is passed into the
atrial cavity, the follicle-cells with which it is surrounded
forming an adhesion to the wall of the cavity, and later
modifying to form a structure recalling the placenta of the
Mammalian Vertebrates by which nourishment is conveyed
from the parent to the embryo. As the result of the devel()]i-
ment of this ovum the non-sexual form {B) is produced, which
is characterized not only by its general form, but also by the
possession of a stolon {st) arising from the branchial sac iust
irPE PBOTOcaOBDATA. ^35
behind the posterior end of the endostvie Thi, «(^i
eventual^, divides into a large number of pX each f ^^
after undergoing certain somewhat complioa ed >;l,if;,r i
position on the stolon, develops into Z e fal t^Lf
2 r"fn^tz:',:trr a'^^inT'^^^^^
iriJJrsii^i^tvs^^^^^^^^^^^
into the non.sexual form (Kg 291 Jri'l,. T'' T^*^^
possession of nine circular m« J! .^ ] diaractenzed by the
.eea some distance ^^:i:^:::'7t^^:,
tlie boay, a ventral stolon (st^ anrl l a 7 ^
directed process (.,, From^t t olol aribr^tT
rior:nX-lt't::d^° t'^ ^'^«- — e\:?£
.i.emselvesZtgrattX~{rd1r^r'
means of amceboid cells, prob.blv n^^f. P *■' . ''^"^' ''^
»ttach themselves in pair; £ t ba'se of eahtd?/'""
to convey it to the dorsal process uLn t, ■ ""^ ""'"^
Uds arrange themselves inSiree ,^„,, t,ie i -r'T"', "'"
lateral rows developing into form, « ^ li" '^'"'^r'^ °^ '''^
resulting from the development of the buds ottT T "'°'^
The lateral buds when fre^Iv ,L i T "'*' """'"'" '■°»--
the possession of a "i t,nS°'' T "''r'"'^"^**" "^^
- i_i„e oiauchial aperture, which occupies
r^T-^fi^
636
INVERTEBRATE MORPHOLOOY.
almost the entire length of one side of the body and leads into
a branchial sac whose stigmata ojjeu directly to the exterior,
the atrial cavity disappearing during the course of develop-
ment. The intestine is well developed, but the muscles are
but slightly indicated, while the reproductive organs, rudi-
ot en li St
P'iG. 291.-^1, Tin: Non-sexual, and B, the Skxual, Foum of DolioUim
(after Ulianin).
cl = cloiutt. i - iult-'StiiK".
(//) = dorsal process. n = iifrve-giiiigliou.
en = eiitloslylc. ot = otocyst.
g = reproduotlvu orgau. M = plinryu.x.
h = heurt. «< -• stolon.
ments of which were present in the young buds, complt'tcly
atrophy during tlie process of dfMelopment. Thusc ImuIs
are incapable of lending a free existence, serving only us
nutritive and res])iratory individuals for the median buds, as
well as for the parent, whose digestive tract deg(uierates, its
muscle-bands and nervous system at the same time umlor-
OF Doliolum
rrPB PUOrocilOHDATA. J37
goiiig enlai-semeut, so tlmt it serves ev^nh„?i
iiiJiviaaal for the eutire ■,.,„,T , '''^"'•"'"y •is a locomotor
With recarilU H "*'«"'*'"'"'' °' ""'"iJnals.
occur. ctTiu Xt;":;" '"r" ""'"■'""- °' oP'-ou
1'ei.g set free, develop ill" '"'■*-' '" ™^ "-"-rit.v all,
■nechau process upou which bura'fotV Tf '' ™''""'
to the orij-in of these buds that tL r^ '' '" '"W""'
exists. According to oue v ew ' T" "' ""'"'»''
ventral process which is"3e. uf aT!"'" "?'' '"" "'^
Uiird generation, while acm,! f ^, " "■"' ''epreseDt a
certaiS member of he ma 'I '" » """*'• "^>^ "--^ -«
tl.e forms bearing thttl ^ ' 't" vt X h ' ''^r"''"""";
serving us nurses for them TOi . ' "'*'«''* ""'1
l^owever. the buds eventn.'.ll :"' """^ '"' "'"'■ °"«i"^
'-«vid„;i., (f!^"'L 1 ;^^Ui:i,'rar'/"'" ■^^^""'
.nenced. The two views as ioiktoXlnDju "' "","'-
schematically represented thus : "" '""^' ^«
Ovum =. non-sexual form^Nurses
Nutritive individuals
-Nutritive individuals
f^oxual forms— Ova
Ovum --. non-sexual form!
'Nutritive individuals
'Nurses
- S(;xual forms Qyji
Nutritive individuals
'-'«-! into oi,h, iaper 1 ui^'s tI' '"f ' ''^ '""•«'"« '^^'"^ 1''-
"i«k and lead, nito a ^^:^ClZ:iJt'"T "" "" '"" ""''■"- •^' "-
l<"ms and the inte.stine and vis ,••».; I ';""""" '' ^■'""l-'.ratively
'•- form of a nucleus. Noth . ' 'V't '" """'"'^ '""--1 ^"«<-t''«-'r iu
this form. " ' ''' ^'^ '^""^^" "« to Hie life-histor.v of
Affl»it>(s of the Vriirhiivih, ti
"■"' M,„ ,■,,,.:,„„,„, ,:; ;; :, ■™^'i,:;;;.;;:,:.'"'" ■■•"™ '"■■ ■> la,.
»'■"! I.... ...any „„„„„„„ siruolun,! f,.. I ,, "" '"'''""l" 1">-
a I". TI, i.,M,., ,/.'.,,;:"■;'''■■■',;•"'''-■ tl«„. ,„ ,„,
chordat
"iitin line of cvolut
I .'iiid ieadiny (<> tjw. v„r(,.|jj.jjj., -j
lie e
'•""■("|)res(.,it.'(| hv (iirl-r,,!,
■'•Hy stages of devch.i.ment
INVERTEBRATE MORPHOLOGY.
638
of the simple Tunicates (see text-books of embryology) are so very siunlar
to those oiAmpkioxus that it must be concluded that he evolution ot 1
Uvochor.iaandCephalochorda proceeded for some distance along sim.Ui
lines, and the general affinities of the Protoehordata may possibly be mdi-
cated by a scheme thus :
Vcrtebrata
Cephalochorda
llemichorda
Ancestral
Urochorda
'rotochordata
T-ikinu tlie larval Tunicates as a basis for comparison, we And as
fettrnv 'on n o ito them and Amt>kio.us a dorsal nervous syste.n ans-
;« ' an magiiution of the ectod.rm and extending the entire length
« the dv in the anterior porthm.l.e lumen of the nerve-cord expands
:: ;!;:::;t;in .^..^. m ..../<>,.. opens in eany ^ages t. t lie ^t...or
■i.ul in the Tunicates into the anterior portion of the bianchul^ac .t,
Z ec odermal portion, the canal of communication in lie latter to.n .
osin Tnl tcf stages its connection with the brain and fon.ung the sub-
^ Ida An'urial cavity occurs in both, which, th.ugh ans.ng in a
^ u. iKit diiferent manner in the two groups, nevertheless sc.nis qu e
h oU Otis, an.l homologies have also been pointe.l out between the
• r^^^^^ The increased lu.n.ber of stigmata and their arrange-
,^ U,e Tunicates is a secondary character resulting probably from he
: :n;:x:s;ence ; and the development of the test and the H"'-.- o ^;
„„(„,,,ovdtothetail are also probably see.mdary characto.s 11".'^^'
bhinces are important one., ami when taken into eous.deratio„ with the
embryonic development point very stmuglv to a close "A"" >;
Xs re-mrds the relati<.nships of the various groups of I .o<'ho.d.v to on.,
.noi er n tsLlerabie .lillV.vnce of opinion exists. The Appeudu-ulanans
" ^ .1 . Sim., se..m to be the most primitive of all the orders pres..,.
rtain remarkable pecul.arities, such as the separate openings o the at. 1
TviU ^ and the amis, and some authors are inclined to reganl thnn no a
■ u tive forms, but as sexualiv-ma.ure larva- of sessile lonns m w ue ■
e«t had alreadv developed an.l de.^eneratum tar a.lvaneed. As.egaids
^erl ai i"«f L
ron en teveral groups originating independently, all the members n..t
" ; l:^,M le/froln a,i ancestral simple forn.. bn. some fnmi one
Ir and others fro.u uuother. uuU .o on. The ThaUu..n, tlnuUy. ha.e
very siiuilar
ntion of the
long similar
bly be indi-
TYPE PROTOCUORDATA.
, wo fliid as
.system uris-
ontirc length
cord expands
1 the exterior
'hial sae, i.e.,
latter forms
ning the sub-
li arising in ii
a seems ([uite
between tlu;
heir arrange-
)al)ly from th(^
litiition of the
. The resem-
itiou with the
[•horda to onc^
(Midieiilarians,
irders, present
ijs of tlie atrial
rd them not as
•ms in wiiich a
I. As regards
nost j»rijnitive,
iisilioi\ of noli
oehi really I"
' nuMubers not
Dtne from one
!i lliudlv. have
639
probably been derived fiv»« „
affinities in its b^n '^ S^t/f^'o^^^'"" ^"^^'^"^^ ^-^n
solitary not necessarily indicating a\,rimitTv. ? '"'"' ^"^'^''^"als being
posite forms no organic union ext sCe „ t^"' '' """^ '" ^"« «"'"-
colony when they have readied m ituHfv .. ' ''^"^"^ individuals of the
rather aggregations than c I'^t f^," ^'^' *'" ^*'"^"*^^ ^-''--^^ -«
«oc,althan colonial or oven composite ™' '"''**^ Properly termed
SUBKINGDOMMETAZOA.
TYPE PROTOCmiil)AT\
I. Class HEMrcHouDA.-I3ody divided into three distinet •
c'liord a .small flngerlike div. H . '■'^"'"'' ^ "^to-
from anterior po.-t on of d ' ? '^^"J^^^"'^' ^V.rwards
retains connection ^""''''' '"''"'^ ^^'^'^ ^vinch it
1. Order I^e,v6ranc/na. - .sessile colonial f
;'''on.se- intestine bent u^;^^^^ '^^'^-^'"^' a
lopliophorelike, tentacle-beirim , 1' " '''^'"' ^^■'"'
cus, Rhahaopleura ° P'ocesses. Ceph^Uodis.
2. Order E,itiroj,neusta.~Fvoo form« ,. f .
-retingatest; i;::3su"l"^./""'"r "''"'^^ ' "^^
lophopi,orelike , roc esse Z ' , '"" '■'^''•^" "'^ ''«"*
n. Class CE.MiAL(,cHo,M)A.-Frec form .; , ^"f "'"^'"-^''^-v-
bodynotdivi:^tt:;r;;:^;;«;;;--tsecretingatest;
ous metameres ; .iot<,clH , ^ L r"' "" I'"""-
dige.stive tract and traver.i,. / ^ separated fn,,,,
body, .l.,;./.-,;:;;: ''""•^'"^' ^'"^^ -^^ire length of the
nJ. Class UROCHOHlu.—Sc'ssili. r>. f,. , .
-1 »i".wu.„ ,.„ i,„n..,. '„'!1.' '''''"' ■■'*"""
1. Suborder .l.vcvV/m. .v/W, , 1 ' "••'"""^"" a.iult.
b-.g. Sinllou ZL Neapol, ix, 1889.
E R. Lankester and A. Willey, The Derelopment of the Atrial Chamber of
Ainphioxtix. Quaiteily Journ. Microscop. Sciciioc, xxxi. 1890.
F. E. Weill. Excretory Tubules tn Amphioxus lanceolatus. Quarterly Joiuii.
Microscop. Sciouce, xxxi, 1890.
i a|)er by
Uiifv.. fj
T^PE PROTOCBORDATA.
nation of
A. Wllley. The Late T — '^^^^. g^j
V of the Vertebrates. Ne^ York, 1894.
C. Kupffer. i?,-, ^^„,„,„'^' ^""^ «^''- x, 1866. ^««(/«««. 3Ienioires
I, 1872. ^'' -^^''^^^^iV*. Arciiivea do 7o.i ^
H-'ieLaca.e-Buthiers Te. A r " '^ "^^^^ -'--t geuerale.
A- Kowalewsky Ced , ' Archives ,Ie
^^ toM.ie, X, 1874. ' ''"^'"''^"^"ff^ierAm-dien. Archiv fn- •,
*• van Benaden et C Juiin A • ^"0"ogi.,
C M«url«. A , '"■'■''"■<■» ■'« Biol., VI
^"Pt'i- bv .>[ M Ar . ,;'^'' " Moaoqranh Win.
'"'^''' °- ''""*'' '"'"IS ilc.pkiua
Grorip
roman tj
ACANTl
Acant/h
ACAKIJN
Acervul
Achther
Acicvla
Acineta,
Aenum,
ACCELA,
ACOTYL
ACRASP)
Aclinian
Actinovh
Actinovii
Aetinoph
ActinoHpi
ACUJ,EA1
^^ga, 41 i
u-EoUs, ai
^'Eolosomi
^Hquorea,
^■Eschna,
Affalina, I
Agilena, ■
Aglaophei,
Afirion, 5(
Aiptmia,
Alc.iope, 2
Alcippe, 31
Alcyonai
Alcyonclla
AlcyonnUu
AUyo Ilium
Ali,oiocu<:i
Alpheus, 4]
• /
INDEX OF PROPER NAMES.
roman type. capitals, generic names in italics, and popular names in
ACANTHOCEPIIALA, 179, 183
Acanthometra, 20, 39
AcAUiNA. 45y, 458
Acertularia. 17, 38
Achtheres, 397, 423
Acicula, 322
Acineta, 36, 39
Acnuta, 364
ActELA, 132, 1G9
ACOTYLEA, 139, 169
ACUASPEDA, 97
Acliniun, 114
Actinometra, 542, 592
Actinomma, 39
Actinophrys, 17, 39
Actinosphcerimn, 20, 89
ACUJ,EATA, ,'^27
-*;9rt, 415, 424
.iJolis, 315, 304
^-Eolosoma, 219. 251
^■hJquorea, 80, 116
^■Eschna, noo, 526
Af/alma, 92, 116
Agdena, 450, 458
Afilmphenia, 87, 116
Av'Vo//, 506. 526
AipUuia, 113. 117
Ali'iopc, 212, 251
Alrippe, 399, 423
Ai.cYONAiu/i';, 108, 117
Alcyondla, 261, 274
AlcyonuUum, 261, 274
Alcyouium, 108, 117
ALi,oi<»ca:LA, 133, 169
Alp/ieus, 412, 424
Amaroecium, 629, 689
Amceba, 15, 38
Amphineuka, 284, 363
Amphioxus, 608, 639
Amphipoda, 416, 424
Amphiporus, 167, 170
Amphitrite, 213, 251
AvqMura, 564, 592
Atnpullaria, 308, 364
Anubolia, 515, 527
Aiiachcftu, 218, 251
Anulgen, 453, 459
Anasii, 510, ,527
Anchorella, 397, 423
A)iel/», 518, 527
Aplynia, 313, 364
Apod A, 593
Api^ixliculiiria, 636, 089
ApHindiH, 414, 424
APTEt;
luuiA, .wi, 526
-4j!JM«, 387, 423
648
€44
INDEX OF PROPER NAMES.
ii
AUACIINIDA, 435
AuANii.«, 448, 453
Arbacia, 580, 593
Area, 339, 365
Aveella, 16, 38
AUCIUANNKUD^, 211, 251
Archigetes, 161, 170
Aricia, 309, 251
ArenicoUi, 209, 251
Argiope, 271, 274
Argonauta, 359, 365
Argulus, 397, 423
Avion, 316, 364
ArmadiUidium, 414, 424
Artemia, 386
AuTHKoroDA, 368, 523
AUTUHOSTKACA, 413, 424
Ascavis, 48, 177, 182
AsciDiACE.K, 627, 639
Ast'ioi/K coMi'osiT^:, 627, 639
Asciui^: siMrucES, 627, 639
Asc'iiUiins, 617
Ascopodaria, 256, 274
ASCOTHOKACIDA, 403
Asellus, 414, 424
Asperg ilium, 329
Aspidiotits, 510, 527
Asplanchna. 189, 200
Asterias, 550, 592
Asterina, 552, 592
Asi'EKOiDEA, 552, 592
Asthenosoma, 570, 593
Asirangia, 114, 117
Astropectcn, 556, 592
Aslrophi/toii, 561, 593
Atalanta, 309, 364
JKaiC, 453, 459
AtropoK, 509, 526
^«««, 451, 458
Aitrelia, 101, 117
AUTOFl-AGKLI-ATA, 28, 39
AiUolytus, 212, 251
Balanoglossus, 601, 639
Balamis, 400, 423
Baruiicles, 398
UA8OMMATt)PU0UA, 317, 364
lidellara, 136, 170
Beacliflea, 416
Bees, 518
Beetles, 512
Belemnites, 360
Iklostoma, 510, 527
i?,'?w, 121, 126
Bipalium, 136, 170
Z?M-5r«s, 412, 424
Blastoids, 550
Bolina, 124, 126
Bolteuia, 628, 639
Bombus, 518, 527
Bonellia, 241, 253
Jiook-seorpion, 444
Bopyrus, 415, 424
Bothriocephalus, 153, 170
Botvyllus, 631, 639
BntchiiiHS, 513, 527
Brachiontts, 189, 200
Bkachiopoua, 268, 274
Bkacuyuka, 412, 424
Branchellion, 228, 253
Buanciiiopoda, 885, 423
Bvanchiostoma, 608
Branchipus, 386, 123
Bkanciiiuka, 397, 423
Brisinga, 553, 593
Bnstle-tails. 501
Hrillle-stiirs, 561
BiiYozoA, 355
Biigi, 510
Bugula, ,262, 274
jB«;/«, 313, 364
i?«rt«W, 510, S
^'inndela, 513
QidariH, 530, j
IJSDEX
(^amponotus, 518, n^l
Campylaspia, 408, 434
Cancer, 413, 424
G^mthocamptm, 806, 433
Capitella, 206, 251
Capretla, 416, 434
(Jm-abus, 518, 527
Garavdla, 92, 116
Cariiuiria^ 309, 364
Garinella, 106, 170
C'arpocapm, 516, 527
(iNATnA, 186, 200
^iKHoHotus, 196, 200
C|h^:t()poda, 304, 351
('/Kirybdea, 101, II7
('fielifer, 443, 458
Oheriies, 444, 4,158
Vhllodon, 34, 39
OlIILofjNATHA, 483
C'lULopoDA, 484, 525
<'iiju)sToMATA, 262, 274
C'nrodota, .585, 593
^''''ito/i, 389, 864
(^"litimelhts, 388, 364
fl'lumydomonas, 31, 39
^''ondracnnthm. 397, 423
<-''iryaopa, 514, 527
^^wififffi, 510, 537
<^<<-indeia, 513, 537
ft'/'*m, 530, 593
CiLIATA, 33, 39
C'lUiuiiPKDiA, 398, 433
C'l-ADOCKUA, 388, 423
(-''urn, 339
Clat/irulina, 18, 39
tVaoa. 87, 116
ClavelUna, 637, 639
Clej)sine, 336, 253
6Vitf/<«, 74, 1J5
CVi.Me, 814, 304
Clmocainpu, 5i6, 537
('iymeneUu, 304 '
OlypeoMer, 581, 593
Cmi.kastuoioka, 581, 593
f-<'A««, 513, 537
^'NIUAHfA, 76, 116
COCCID/K, 510
(^'OCCIDIA, 34
Cocci iiella, 513, 527
t'ockroiicli, 504
Codosifja, 28, 89
Cuil.KNTKKA, 68, 115
Cmloplmm, 135
Coi.Ecn'TKUA, 512, 527
COLLKMHOLA, 503, 526
CoUosHendeift, 464
Colpidiiiw, 37, 39
Volpoda, 36. 39
Coiivolutii, 182, 169
CoiMci'ODA. 393, 423
C'oial, 114
Coraltium, 108, 117
t'ouNAcusroNoiA, 73, 115
Cwophiiim, 417, 424
CoHUODKNTfA. 507, 526
GorycivuH, 396, 433 '
Corydali8, 514, 527
^w^/ic, 87, 116
CoTYMiA, 139, 170
Cml)s. 412
Cmnia, 271, 274
Oniylislj, 413
Crickels, 504
CJiiNoiDKA, 541, 593
Cvisia, 274
CriHtateUa, 260, 274
CnusTACKA, 368
Chyptopkntameha, 527
645
646
INDEX OF PliOFER NAMES.
Cryptophialus, 399, 423
C'jiYPTOTETUAMEHA, 527
Cteniza, 452, 458
CteiiodHlus, 58, 222
Ctenopiiora, 120, 126
Ctenoplana, 125
Ctenostomata, 262, 274
TUBOMEDUS^. 101, 117
Cucumaria, 585, 593
Vulex, 520, 528
CuMACEA. 407, 424
Cunina, 96, 116
Cunqctantha, 84, 116
CURCULIONID.E, 512, 527
Cuspidaria, ;i89, 365
Cyamua, 416, 424
Cyanea, 101, 116
Cyclnti, 3:39, L
Cyclops, 396, -. ,!3
Cyclostoma, 30t ' 4
Cyclostomata, 262, 274
CymhuUopm, 314, 364
Cymothoa, 415, 424
Cytiips, 518, 528
Cynthia, 628. 639
Cyphopliihulmus, 447, 458
(Vp^vpa, 307, 364
Cypridina, 391, 423
C:y;»'is, 391, 423
C'ystoflagellata, 30, 39
Cystolds, 550
Cy there, 391, 423
Dactylopius, 510, 527
Daphnia, 388, 423
Daudebardia, 316, 364
Decapoda (Cepbiilopoda), 359, 365
Decapoda (Crustacea), 410, 424
i)emrf, 585, 593
Demodex, 453, 458
BendrociBlum, 136, 170
Dendrognster. 403, 423
Dentalinm, 323, 364
L'-rmnlekhus, 453, 458
Deumapteua, 504, 526
/fero, 218, 251
Desmosticha, 580, 593
Dindema, 580, 593
Diopheromera, 505, 526
DiantyliH, 408, 424
Dibkanciiia, 359, 365
Dicyema, 64
DiCYEMiu.*;, 64
Dideinnum, 630, 639
Difflugia, 16, 38
Dinobryon, 28, 39
Dinoflaoellata, 30, 39
DiiiophUuH, 198, :iOO
JJiopaira, 212, 251
DioivcAUDiA, 305, 364
Diphyes, 92, 116
Z>«>?(!«a;, 506, 526
DiPLopoDA, 482, 525
Diplozoon, 147
DiPNEUMONEs, 452, 458
Diporpa, 147
DiPTEUA, 519, 528
DiscoMEDus^:, 101, 117
IJincosoma, 114, 117
Distaplia, 629, 639
DiSTOME^, 147, 170
Distomum, 147, 170
Dochmius, 177, 182
LoUolum, 635, 640
Uuiidermi, 287, 364
Z>o?'M, 315, 364
Boryphora, 513, 527
Dragou-flies, 506
Earwigs, 504
EcAuuiNEs, 269, 274
Echinarachnius, r81, 593
Echinocucuntis, 585
ECIIINODEKA, 184, 200
Echinoderes, 184, 200
EciIINODEUMA, 531
EcHiNoiuEA, 570, 592
Echinorhynchus, 180, 18S
EciiiuuE,*;, 240, 252
Echinrns, 240, 252
EcTOPuocTA, 257, 274
Edriophthalmata, 413
Edwardsid, 117
EowAKDsi^:, 109, 117
Elasipoda, 585, 593
Er.ATEKin.K, 513, 537
Elpidi
Endo]
Ensate
Enteh
Entom
Entoni
Epeira,
Epherru
Epheme
Ephyda
ErgasUi
Eruani
Esperell,
Estheria
Eucope,
EUCOPEI
Eudendi\
Euglena,
Euglypha
EULAMEI
EnNEMAl
Eupagun
Euphausu
Euplectelli
EuRYALrn
Eurylepta,
JSurypaui't
EURYPTER
EuTypterus
EURYSTOM]
Eiiscorpius,
Empongia,
Evadne, 38fe
EacelUna, 3
Eilaria, 177,
FiLIBRANCH
Eiona, 311
Fissurella, 3(
Elagellata
I'^Jies, 519
Eloscularia^
^''lustra, 261,
EoHAMr]snFEp
^orficula, 50J
Formica, 518,
Fredericella, 2
^nngia, Hi, 1
IN3BX OF PROPER NAMES.
Elpidia, 585, 593
Endoprocta, 256. 274
Enmtella, 339, 365
Enteropneusta, 601, 639
Entomostraca, 385, 423
Entoniacus, 415, 424
Epeira, 450, 458
Ephemera, 504, 526
Ephemeridce, 505, 526
Ephydatia, 73, 115
Evgasilua, 396, 423
Erkantia, 211, 251
Esi)ereUa, 75, 115
Estheria, 387, 423
Eucope, 86, 116
Eucopepoda, 396, 423
Eudendriutn, 93, 116
Euglena, 29, 40
Euglypha, 16, 39
EULAMELLIBRANCHrA, 339, 365
EUNEMATODA, 174, 182
Eupagurus, 411, 424
Euphauaia, 406, 424
Euplectella, 74, us
EuRYALiDA. 569, 592
Eurylepta, 139, no
Eurypauropus, 482, 525
E UR YPTERID^, 433
Eurypterus, 433
EuRYSToME^j, 125, 126
Euscorpius, 443, 458
Euspongia, 73, 115
^i'ttcJwe, 388, 433
FacelUna, 315, 364
Eilaria, m, iS2
PlUBRANCHIA, 339, 365
Eiona, 311
Eissurella, 305, 364
Elagellata, 28, 39
Elies, 519
Elosculana, 189, 200
Eliistra, 261, 274
EoRAMlytFERA, 15, 39
Eorficula, 504, 526*
Formica, 518, 527
Eredericella, 260, 274
Eungia, 114, 117
647
Galeodes, 445, 458
Oamasus, 453, 459
(^arnmarua, 416, 424
Gasteropoda, 293, 364
(iaateiopteron, 313
Oecarcinua, 412, 424
Oelaaimua, 412, 424
Geometrid^, 517, 527
Geophilua, 484. 525
Gepiiyrea, 237, 253
(^eryonia, 85, il6
Oibbocellum, 447, 458
Olobigerin", 17, 39
Olomeria, 483, 525
Gnathobdellxd^, 236. 251
l^onactinia, 111, 117
Oonodactyhta, 409, 424
Oonoleptua, 448, 458
GoRDiACEA, 178, 183
Gordiua, 178, 183
Gorgonia, 108, I17
Grantia, 73, 115
Giasslioppeis, 504
Gregarinida, 24, 39
Gromia, 16, 39
Gryllotalpa, 504, 526
Gryllua, 504, 526
G'j^jfte, 136, 170
Gyainol/emata, 261, 274
Gymnosomata, 314, 364
Gyrinna, 513, 527
Gyrodactylua, 14 7, 179
Il'vmenteria, 236
Ilalcampa, 113, II7
Halecium, 87, 116
HalioUa, 305, 364
lialiaarca, 74, 115
Ilnlohates, 510, 527
Halorypris, 391, 403
Halodrilm, 227
Harpacticus, 396, 423
■'^'rpahia, 513, 527
Harvest-men, 448
Harvest-mite, 453
Harvest-spider, 447
JIdiopora, 109
Uelioaphmra, I9, gg
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.v.
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i^vi
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IMAGE EVALUATION
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1.0
I.I
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Sciences
Corporation
1^ 1^ 1 2.2
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648
INDEX OF PROPER NAMES.
Heliozoa, 17, 39
Helix, 316. 364
Hemichokda, 596, 639
Hemiptkka 510, 527
Hermit Crab, 411
Heaione, 207, 251
Heterodera, 176, 183
Heteuomeua, 527
Iletei-onereis, 216
Heteropoda, 309, 364
Heterotuicha, 40
Hexactim^, 113, 117
Hexarthra, 194, 200
Eippa, 411, 424
Hirudinea, 228, 251
Hirudo, 236, 251
Uolopus, 541, 592
Holothuria, 585, 593
HOI.OTHUROIDEA, 584, 593
HOLOTRICHA, 40
Homariis, 412, 424
HOMOPTERA, 510, 527
HOPLONEMERTINI, 167, 170
Horseshoe Crab, 428
HVALOSPOl.GI^. 74, 115
Ilydra, 58, 83, 116
Hydrnchna, 453, 459
Uydractinia, 58 87, 116
Hydrari.*:, 83, 116
Hv'DUOCORALMN^., 89, 116
Hydromedus/E, 78, 116
Hydrometra, 510, 527
UydropJiilus, 518, 527
Hymenoptera, 517, 527
Ilyocrinua, 542, 592
Hypotriciia, 40
lanthina, 807, 864
ma, 401, 428
Ichneumon, 528
Ii'hthydium, 196, 200
IcIMyolHleUa, 228, 252
Tdotea,iA\ 424
Idyia, 125, 126
Infusoria, 38, 40
Inbkcta. 487, 52C
/«>. 108, 117
IsopoDA, 414, 424
lulus, 483, 525
Ixodes, 453, 459
/awM«, 311, 364
King-crab, 428
Kolga, 589
Labia, 526
Lacmularia, 189, 200
Lam::li.ibranchia, 326
Lampyris, 513, 527
Larvacea, 626, 639
Laura, 403, 423
Leiobunum, 448, 458
Lepas, 399, 423
Lepidonotus, 212, 251
LEPiDOPTEr,A, 515, 527
Lepisma, 502, 526
Lepiodiscus, 3C 39
Leptodora, 418
Leptogorgia, 108, 117
Leptomedus^, 85, 116
Leptoplana, 139, 170
Leptosthaca, 404, 423
Lernom. 397, 423
Leucosolenia, 73, 115
Libellula, 506, 526
Libinia, 412, 424
Ligula, 152, 170
Limacina, 814, 364
Limapomia, 315, 864
Limax, 316, 864
Limnadia, 387, 423
Limuaa, 316, 364
Liinnetis, 887, 428
Limulus, 427
IJnguln, 271. 274
LioVieum, 509. 526
Liriope, 85, 116
Lithobius, 485, 525
Lobster. 412
/x>%o, 359, 865
Lopfiopus, 261, 274
Lo^rosorna, 256, 274
l.ucei'naria, 100, 116
Zuci^fr, 411, 434
iT.T/iV^ui, 568, 692
LUM
Lum
Lycoi
Lysic
Lysio
Lyttu
Macrc
Macro
Macr<
J*Iacim
Mad I e^
Malucc
Malac
Malac
AfALAC(
Malac<
Malloj
Margeli,
May-fly,
Melicertt
M-llita,
Meloe, 5]
Melolonti
Melophai
Membran
Mernm, ]
Mertensia
Mesostovu
Mesozoa,
Metazoa,
Metridium
Mierogaxle
Microgrom
MrcHoLEp
Microstoim
Miliola, 16,
Millcjxira, i
^'illipodes,
Elites. 453
Mnemiopttia^
Modiolaria,
yfoina, 388,
^foira. 588,
'^(olguld, 62f
Molpi.X OF PROPER NAME8.
649
Monostomum, 147, 170
MoNo'iOcARDIA, 306, 364
MoHoius, 134. 169
Aimeria. 585, 593
'l/Msca, 020. 5^i8
Musse), 339
^y<'ypodn, 412. 434
ONATA, 506, 536
650
INDEX OF PROPER NAMES.
Oligoch^ta, 218, 251
OinmastrepJm, 359, 365
Onchidium, 316, 364
Oniacus, 414, 424
Onychophora, 475
Opalina, 36, 39
Ophiacti8, 566, 592
Ophioderma, 561, 592
Oplmlepia, 567, 592
Ophiomyxa, 561, 562
Ophiothrix, 564, 592
Ophiura, 592
Ophiubida, 569, 592
Ophiuroidba. 561, 592
Opilio, 448, 458
OPISTHOBRANCHIA, 310, 364
Oractis, 111, 117
Orgyia, 516. 527
Oribatea, 453, 459
Orthonectida, 65
Orthoptera, 504, 526
OSTRACODA, 391, 428
Ostrea, 339, 365
Oxyuris, 177, 183
Oyster, 339
Palmmon, 413
Palmmonetes, 412, 484
Pal^kocrinida, 551
Pal^onemertini, 166, 170
Palinurua, 421
Paludicella, 261, 274
Paludina, 807, 864
Palythoa, 112. 117
Pandartta, 396, 428
Punorpa, 514, 527
Panorpata, 514, 537
Papilio, 527
Paranmcium, 85, 89
Patella, 305. 864
Pauuopoda, 481, 535
Pauroptia, 482, 525
PiiUa, 409, 424
Staphylinid^e, 512, 537
Starfish, 553
STAUROMEDUSiE, 100, 116
Stentor, 35, 40
Sternaspis, 343
Stomatopoda. 408, 424
Sloinclophus, 101, 117
Slouu-aies, 507
Stroml/ua, 307, 364
Strongylocentroiua, r)80, 593
Strongylosoma, 184, 520
Stylaster, 90, 116
%;eWrt, 314, 364
Siylochus, 141, 170
STYLOMMATOPnOUA, 318, 364
Stylonychia, 40
SucToiUA, 30, 40
Sim-animnlcule, 17
Syllia, 313, 351
Symphyla, 48C, 536
Synapta, 633, 040
Synccelidium, 186, 170
Tabanus, 520, 528
Tmnia, 153, 170
Tanaia, 414, 424
Tanysiylum, 463
Tardigrada, 466
rc«Jja, 113, 117
TECTIBRANCHfA, 313, 364
Tegenaria, 45(t, 458
7e/«i, 517, 537
Tentaculata. 134, 126
TfTPhella, 213, 351
Terebkantia, 537
Tevebratulina, 371, 274
Teredo, 839. 365
Tfe/'me.'i, 508, 526
Termites, 507
Teaa&ra, 100, 116
tk8ticahdine8, 269, 274
Tetrabranchia, 857, 365
Tetranychua, 454, 459
Tetrapnettmones, 452, 458
Tetraatemma. 167, 170
Textularia, 17, 89
Tualaaaema, 241, 253
niamsaianthua, 114, 117
INDEX
TliaUmicolla, 18, 39
Thaliacea, 633, 640
Thaumaiocrinus, 543, 593
Thecasomata, 314, 364
Thelyphonus, 446, 458
Theridium, 450, 458
Thohacostraca, 406, 434
Thripa, 510, 536
Thyone, 587. 593
Thtsanopteka, 509, 536
Thysanozoon, 139, 170
Thtsanura, 501.' 636
Ticks, 453
Tinea, 516, 537
Tracheata, 469
Trachydermon, 289, 364
Trachymedus^, 85, 116
Trematoda, 143, 170
Tremoctopua, 859, 365
TrianopJm-ua, 153, 170
TricJiaater, 569^ 593
Trichina, 176, 183
TrichoeepJialua, 177, 183
Trichodectea, 509, 526
TricJioplax, 63
Trichoptera, 515, 527
Tricladea, 136, 169
Triatomum, 147, 170
Trodmphcera, 194, 300
Troc/iua, 305, 864
Trombidium, 453, 459
'Jubipora, 108, 117
Tubulana, 89, 116
TUBULARI^. 87, 116
TUNICATA, 617
OF -mopeh names.
\ TURBELLARIA, 130, 169
Turbo, 305, 364
Tyroglyphua, 453, 459
Unio, 339, 365
Urnatelia, 356, 374
Urochorda, 617, 639
Vaginula, 316, 364
Vampyrella, 23. 39
Vanessa, 517, 537
Velella, 93, 116
Vemis, 339, 335
Venus' ginJle, I3i
Vermilia, 309
Veapa, 518
Fb^ioa;, 30, 33, 40
Vortex, 135, 169
Vortieella, 34, 40
Waldheimia, 271, 374
Walking Stick, 504
Wasps, 518
WLeel-auimalcule, 189
WLite ants. 507
Wood louse, 414
Xiphosura, 437
Toldia, 339, 365
ZOANTHE^, 118, 117
Zoanthus, II3, 117
ZOOXANTHELL^, 80
Zoroaster, 553, 593
668
»."
605; Ecbinoldea, 579; Qep^yZ',
~a9; Polycbaeta, 207
flconous eyes, 473
Actinotrocha, 249
^iil rectal gland, 305
adliesive cells, 133, 131
alar muscles, 470
albumi-jiparous gland, 312
tocla, 176; Scyphoniedusffi, 103-
Trenmloda, 148; Urochorda 633
amitosis, 9 ' ^°°
ametabolic insect?, 499
amoeboid motion, 15
ampbiaster, 11
ampbidiscs, 76
ampulla, 537
an ten naiy gland, 383
apical plate, 213, 607
arclientcrou, 54
archiceiebrum, 379
Aiistotle's lantern, 578
artbrobraucbia, 410
ascidiozooid, 632
Ascon, 70
aster, 7
^""•"•". 596; Oepbnlocborda. 612; En
leropneusta tiOi- v>, i.
r.09 600. IT , •, ^'^'•"branchia,
■>•'», 000; Urocborda, 622
atrnim (genital), I34
aiiiiniias, 573
Auricularia, 590
aviciilaii-i^ ggg
axial sinus, 538
INDEX OF SUBJECTS.
Basement-membrane, 127
biogenetic Jaw. 143
Bipinnaria, 559
Wviuin, 572, 584
blasfoccBl, 62
blastopore, 54
bbislula, 52
blo^-vascular system. Arachnida 437.
Cepbalocborda, 611; Cepbalopl'
346; Cbaelopoda. 206. 220- C^!'
cea, 376; Enteropueusta eo^ « '? '
yrea. 238; Hirudinea 2^ M i?'^**"
278; Nemertina 165 P, "^'"''"•
247- T,^ ., ' Pboron dte.
621 xTr "'"• ''"' Urocborda
O'^i , Aipbosuia, 429
Bojanus, organ of, 837
tfrachiolaria, 559
brancbial heart, 347
bmncbial skeleton, Cepbalocborda.
oirf, Enteropneusta, 609
brown body, 267
brown canal, 616
bursa copulatrix. Nematoda. 174 182-
Tracheata, 497- T^^^^.^^^ • '
138 Juibellana, 136,
byssus gland, 329
Calamistrum, 449
f^alcar, 192
calciferous glands, 220
calyptoblastic, 86
caryolympb, 6
caryoplasm, 5
cell, 4,
cell-division, 9
cellulose, 30, 619
cenogenetic, 143
central cai>sule, 19
ceutrolecitbal, 63
centrosome. 7, 51
cepbalization, Sflo
655
656
INDEX OF SUBJECTS.
ceratn, 815
Cercana, 150
cerci, 489
chambered organ, 546
chela. 373
cheliceroB, 439, 435
chiiisloueuiisin, 296
chilaria, 480
chloragogue-cells, 219, 238
chlorophyll, Flagellatu, 30, 31; Hy-
drariae, 83; lufusoria, 35; Porifern,
78
chordotonal organ, 495
chromatin, 6
chromosome, 11
chrysalis, 500
cilia, 33
cilia-plates, 121
cirrus, 146, 155
cirri, Cephalochorda, 609; Crinoidea,
542; Myzoslomeae, 244; Polychoeta,
204, 205
clavuloe, 574
clitellum. 219. 228
cloaca, Nemutoda, 175, 179; Rotifera.
192; Urochorda, 631
cnidocil, 77
cnidobiast, 77
coelenteron, 77
poelom. 57
coeneuchyme, 108
coeiiosarc, 79
Ccenurus, 158
colony-formation, 5, 8; Anihozoa, 108,
111, 112. 114; Flagellar, 30; Hydro-
medusoe, 78, 85, 87, 91; Polyzoa,
255; Rhizopoda, 21; Urochorda.
628
columella, 90, 107
compiemental males, 401
conjugation, 24. 25, 32, 37
contractile vacuole, 15
corallum, 89
cormus, 41
costse, 107
coxal glands, Arachnida, 441; Xi-
pbosura, 432
crlbellum, 449
ciural glands, Insecta, 502; Myriop-
oda, 485, 487; Protracheuta, 4:9.
crystalline style, 333
ctenidium, 278
Cuvierian oigiins, 588
cynthozooid, 632
Vyphonautes, 264
C'ysticercoid, 158
CysHcercus, 158
cytode, 8
cytoli mph, 4
cytoplasm, 4
Daclylozoid, 90
delaniinution, 55
Desor's larva, 167
deutovnin. 456
development, Acaniliocephala, 182;
Acariiia, 456; Asleroidea, 559;
Brachiopoda, 272; CVplialopoda,
36->; Cestoda, 157; Criuoideii, 551;
Crustacea, 417; Echinoidea, 583;
Enleropneusta, 605; Gasteropoda,
819; Gephyreu, 242; Hirudinea,
237; Hoiothuroidea, 590; Hydro-
medwste, 92; lusecta, 521; Nema-
toda, 176; Nemertina, 167; Oli-
gocliteta, 225; Ophiuroidea, 570;
Pelecypoda, 339; Pentastomidoe,
463; Phoronidfle, 249; Polychteta,
213; Polyzoa, 263; Porifera, 74;
Pycnogonida, 466; Scaphopoda,
324; Scyp} omedusaj, 103; Trenia-
toda, 148; Turbeilaria, 140; Uro-
chorda, &2\\ Xiphosura, 432
digestive gland, Arachnida, 437;
Brachiopoda, 271; Crustacea, 378;
Mollusca, 880; Rotifera, 192;
Xiphosura, 430
digestive system, Amphineura, 28(1;
Arachnida, 437; Brachiopoda, 270;
Cephalocorda, 612; Cephaloiioda.
348; Choetognatha. 187; Chujtopo-
da, 206, 220; Crustacea. 377; Di-
nophiliis, 198; Ecliiuodera, 185;
Echinoderma, 539; Enleropneusta,
605; Gasteropod -, 300; Qastrotricha.
196, Gepliyrea, 238; Hirudinea,
m
INDEX OF SUBJECTS.
231; Mollusca, 279; Myzostome*.
?Ao' i^f™'''^^'"' 174; Nemertina.
lOv; Pelecypoda. 333; Peuiastomi-
doB. 461; Phorouidee, -47; Polyz,oa.
205; Pycuogoiiida. 465; Kotifera.
191; ScapLopoda. 323; Turdigruda.
?!!' J""'"'''^'"' ^'^= Trematoda.
144: Tuibellaria. 133, 135. 136. 138;
Urochorda. 62-J; Xiphosura. 430
dimorphism, sexual, 193, 199 241
395.496 ' '
dimorphism, seasonal, 501.
dissepiment, 107. 187, 202. 270
dissogoiiy, 123
divisio..oflabor,85, 87, 91 (see also
polymorphism)
docoglossate dentition, 306
dorsal organ, 546
dorsal pore, 219
Echinoeoecxis, 158
ectocyst, 255
ectoderm, 54
ectoplasm, 3
elseoblast, 633
elytra, 490
embole, 54
eiicystmeiit. 22, 37
eiidocyst. 255
endoderm, 54
endophragmal system, 375
endoplasm, 3
endopodlte, 373
eudosteruite, 429, 457
endosfyle, Cephalocorda, 614 Uro.
chorda. 622
enterocoel, 57
epliippium, 391
Ephyra, 103
epibole, 54
epipleural folds, 609
epipodite. 373
epipodium, 291
epistome, 247. 260. 597
epithelio-mnscid.ir cells, 80
Erklithus, 422
euconous eyes. 473
excretory system, Acanthocepbala.
657
!*i' ^™P^'«eurtt,287.292; Arach-
nida,437;Brachiopoda.273;Cepha.
locorda. 615; Cephalopo.ia. 853;
Cestoda. 155; Chujtopoda, 210, 222-
Crustacea. 383; Dinophilus, m-
Ijchmodera, 185; Enteropneusta,'
605. Gasteropoda, 302; Gasterotri-
cha,196;Gephyroa.239;Hirudinea,
£ Mollusca. 283; Myzoston.e*.
245; Nematoda. 175; Nemertina.
a!^' ?.f "'^P«''«' 337; Phoronid*.
249; Platyhelminthes. 129; Polv-
fioo ^^'•J''^'' ^^^•■«^'-««ehia. 599.
600; Rot.feru. 193; Scaphopoda,324;
Iracheata. 474; Trematoda, 145'
Turbelhiria, 135, 138; Urochorda.'
o«3; Xiphosura. 432
exopodite. 373
eyes-Amphineura. 292 ; Arachnida.
438; Asteroidea, 559; Cephalochor-
aa. 615; Cephalopoda. 351; Chteto-
g'latha, 188; Chaetopoda, 208; Crus-
tacea. 380; Gasteropoda, 301, 318-
Hirudinea. 234; Hydromedusffi. 82-
Nemertina. 164; Pelecypoda, 335-
Pycnogonidn. 465; Rolifera. 192'
ScyphomedusiB, 99; Tracheata, 472-
Tui-bellaria, 131; Urochorda, 625-
Xiphosura, 431
Fascioles, 574
fat-body, 492
flagellum. 28
flame-cell. 129
follicle-cells. 46
fossa rhomboiilalis. 615
funiculus, 259
Gaslerozooid. 89
gastrula, 53
gemmation, 22
gem mules, 75
genital bursae, 561
germ-cell, 44
germ-layer. 54
OlocJiidium, 339
Goette's larva. 141
gonopolyp, 85
668
INDEX OF SUBJECTS.
gouotheca, 86
greeu-gliuid, 888
gymuoblastic, 87
Htemocyauiu, 278, 377, 429
haemoglobin, 877, 588
hsemolyiupb, 206
halteres, 520
head-kidney, 214, 222
heart— Arapbiueura, 289; Arachnida,
487; Cepbulopoda, 346; Crustacea,
376; Gasteropoda, 298; Pelecypoiia,
332 ; Pycnogouida, 465; Tracbeatii,
470; Urochorda, 621; Xiphosura,
429
Hectocotylua, 856
hemimetabolic insects, 500
herinapbroditism, 44
heterogony, 60, 148, 498
histolysis, 456
holometabolic insects, 500
hook-gland, 462
hydrant h, 79
hydrocaulus, 79
bydrocoel, 535
hydrorhiza, 79
bydrotheca, 79
bypermetamorphosis, 513
hypodermis, 174
hypophysis cerebri, 615, 623
hypostome, 79
Imago, 500
immigration, 55
individuality, 41
ink-bag, 349
interteutacular organ, 260
invagination, 54
Karyokinesis, 9
Keber's organ, 337
Lacunar system, 538
languets, 622
lateral-line organs, 210, 222
Laurer's canal, 146
lemnisci, 181
Lencoti, 71
linin, 6
liver, 614
lopltopbore, 247, 254
lung- books, 436, 457
Madreporiform tubercle, 586
madreporite, 586
malpigbian tubules — Ampbipoda,
417; Arachnida, 487; Tracbeata,
474
mantle, 268, 276, 621
manubrium, 81
mustax, 191
Medusa, 77, 80 ; Craspedote, 81 ;
Gymuophthalmatous, 82 ; Ocel-
late, 82, 89; Vesiculate, 82
megaloestbetes, 292
Megdlopa, 422
mesendoderra, 68, 132
mesenterial filaments, 99, 105
mesentery, 57, 104, 179, 187, 206, 270
mesoblasts, 57, 214, 225, 237
mesoderm, 56
mesoglcea, 68
mesopodium, 296
mesothorax, 488
metagenesis, 60
metamore, 41
metamerism, 43
metamorphosis of insects, 499
Metanaxiplius, 418
metapodium, 296
metathoiax, 488
Metazoea, 421
microestbetes, 292
micronucleus, 35, 38
microsomes, 4
mitosis, 9
Morren's gland, 220
Mllller's larva, 141
muscular system — Acantbocepbala,
180; Amphineura, 286, 289; Anllio-
zoa, 166; Brachiopoda, 270; Ceplm-
locborda, 610 ; Cepbalopoda, 348;
Cestoda, 154 ; Cbajtognatba, 187 ;
Chaetopoda, 205, 219; Crustacea,
875; Dinophilus, 198; Ecbiiiodera,
185; Ecbinoderma, 585; Gasleropo-
INDEX OF SUBJECTS.
da, 298; Qastiotiiclin. 196; Hirudi-
^^ 329; Insecla. 492; Nenmtoda,
', • ^^°'^ Ptilecypoda. 882; Tia-
clieata, 469
myotOBi, 610
myopliaues, 36
659
Natipliui, 417
neciocalyx, 9l
Needham's pouch, 855
nematocyst, 77
nephiidia (sec Excretory System)
uephroblasts, 326, 287
nervous system _ Acautl.ocephala,
i81: Amphmeura, 287. 290; Aiach-
DJda. 487 ; BiacliiopodM. 271 • Ce-
Phalochorda. 614; Cephalopoda.
850:Cestoda. 155; Cha^tognatha.
187; Choetopoda. 208, 221 ; Crusta-
cea, 378; Ctenophom, 124; Binophi-
ins, 199; Echinodera, 185 ; Echiiio-
derma. 589 ; Enteropnensia, 605 •
Gasteropoda. 800; Gastrotricha, 197-
Gephyrea. 239; Hirudiuea. 232- Hy*
dromedus8B, 80; Molhjsca, 281 • My.
zostomeaB.244; Nematoda. 175. 179-
Nemertina. 163 ; Pelecypoda, 834;'
Pentastomida,. 461; Phoroi.id(B,247-
PIatyhelminthes.l'>8; Polyz<,a.257;'
Ponfera. 73 ; Pterobrauchia. 599.
600 ; Pycnogonida. 465 ; liotifera.
192; Scaphopoda. 823 ; Tracheata.
JJ|'J''«'"a'«da, 144;TurbeIlaria.
lol, 133, 137 ; Urochorda, 623- Xi-
phosura, 430
neuroblasts, 226, 237
nidamental gland. 812, 355
notochord — Cephalochorda. 612 •
Entero'.-neusta. 603; Pterobranchia'
599, 600; Urochorda, 625
nuclein. 3
nucleolus, 6
nucleus, 5
nymph, 456
Scj^phomedusoB, lOO ; Tracheata.
47^; Xiphosura, 482
omaiatidium - Ch^topoda. 309-
Crustacea. 881; lusecta. 472- Pele-
cypoda. 387; Xiphosura. 431
ooBcia. 263
ootyp, 146
operculum-Gasteropoda, 296- Polv-
zoa, 262; Scorpiouida, 442; Xipho-
sura, 429
organ, 41
°'"fjr f ^^^J'^""^' 337 ; of Cuvier,
Oo8; of Stewart, 576
orthoueurism, 310
osculum, 69
osphradium, 283
otocysts-Chaetopoda, 209; Crusta-
cea, 888; Cteiiophora. 122; Holo-
thuroidea,589;Hydro.ne,lu8ffi,82.
»4, 85. 86; Mollusca. 283 ; Scypho-
medusae. 99; Turbellaria, J31, 132,
184; Urochorda, 625
ovary, 44
ovicell, 268
ovum, 44 ; Fertilization of, 49 • Ma
turation of. 46; Segmentation of
51
Odontoblasts. 280
olfectory organ-Cephalopoda. 853.
Chaetognatha, 188 ; Mollusk. 282 •
PflBdogenesis, 60, 499
pali. 107
palpi. 205
parapodia. 204. 313
paratroch. 213
parenchyma, 128
Parenchymelia, 55
parthenogenesis. 60. 498
paxillsB. 553
pectines, 442
pedicellariae. 574
pedipalps. 435
Pentactma, 591
pereiopod. 410
pericardial glands, 298, 337. 345
pericardium, 278, 437
ptirisarc, 79
peritoneal cells. 205
phaosphere, 489
phosphorescence. - Crustacea, 382;
660
INDEX OF SUBJECTS.
Cystoflagellatii, 32; lusecta, 492;
Urochordu, 682
phruffiiiocoue, 360
Phyllosoma, 421
PHidium, 168
piunules, 542
plasome, 48
plastiu, 3
pleopod, 410
pleiirobrancLia, 410
Fluteus, 570
pueuumtophore, 91
podobniuchia, 410
polii'- bodies, 46, 49
Polian vesicle, 536
pol^p, 76, 78
" polypiue, 255
polymorphism, — Ahyouariae, 109;
lusecta, 497, 500, Polyzoa, 262
(see -ilso divisiou of laboiy
polyspermy, 50
porlril systeai, 612
proboscis, — Acautbocepliala, 180;
Gasteropoda, 300; Myzostomea-,
244; Nemertina, 163
proglottid, 154
proOstracou, 360
propodiiim, 296
profjopyle, 71
proslonuum, 218
prothorax, 488
protopla&m, 2
protcpodit; 573
prototroch, 213
Protizotd, 419
p8et:;Iot^Iiiria, 33
pseudouaviceila, 25
i.aeudopodlum, 14
pteiioglossjite dentition, 308
pupa, 500
Uachi^dossate dentition, 307
radula, 273
Jfedin. 1 19
regeneration, R9
reproduction —Flagellata. 32; Inftiso-
ria, :}«; Mciazoa, 42; Myxosporidia,
87; Ubizopoda, 20; yporozon. 25
leproduciiou,— by budding, 22, 08,
71, 83. m, 114, 215. 256, 266, 627*;
by conjugation. 24, 25, 31. 37; by
divisiou, 21, 37, 58, 114, 227: by
spore - formation, 32, 25. 82, 37;
«exunl, 44
reproductive system.— Acantbocepb-
ula, 181; Ampbiiieura, 287; An-
tbozoa, 105; Aracliniibi, 44) ; Rrach-
iopoda, 272; CcphalochorUa, 617;
Cephalopoda, L54; Oestoda. 155;
Cliieutgnalha. 188; Chuetopoda,
211, 223; Crusli.cea, 384; CliMio-
pbora, 123; DinophiluH, 199; Ec;lii-
uodera, 185; Echiuoderina. 540;
Gasleropoda, 302, 305, 311. 318;
Gasuotricha, 197; Gepbyrea, 240;
Hirudinea, 235; Hydromedusa;, 83,
85, 86; Myzostomea;, ::;46; Iseuiii-
toda, 175, 179; Ne.nerlina, ](jG;
Pe'.ecypoda, 337; Penlasloniida',
462; Platybelminthes, 129; Poly,
zoa, 257, 260; Pterobriincbiii, 6U0;
PycnoL-onida, 466; Rotifcra, 193;
Scypbomedufiw, 98; Traoheata, 474;
Trematoda, 146; Turbellaria. 133,
134, 135, 187, !39; Urocliorda, 623;
Xipbosura, 48£
rt'piiguatorial glands, 488
respiratory system.— A.nneliila, S-^M;
Aracbnida, 436; Asteroidca, .^4;
CephrJochorda. 612; Cephalopoda,
343; Cnstacea 875; Ecliinoidea,
576; Enteropneusta, 601; GastiT-
opoda. 297, 217; Mollusca, 278;
Pelecypoda, 329; Plerobrancbia,
599, 600: Tracbiala, 470; Uro-
chorda, 622; Xiplion-ia, 429
re8|)iratory trees, 240, 5f(8
Rhabditia, 131
rhipidoglossate dentition, 806
./Mtollum, 164
Saoculi, 548
salivary glands, 280, 498
acapboguathite, 410
schizocd'l, 87
foolvx, 158
INDEX OF SUBJPJCm
661
Scyplmtoma, 103
seasonal diiiiojpliism, 501
Semites, 574
septa, 107
setae, 204, 218
seUi-sucs, 304
sexupl dimorphism, )93. 199 241
395, 4f>6 ' '
sbell.-Amphiiieura, 289; Bracbiop.
oda, 269; Cephalopoda, 343, oo7,
360; Gasteropoda, 303, 316; IVle-
cypodrt, 327; Scaphopoilu, 3^2
shell-glaud, 383
siphou, 304. 827, 493, 579
siphouoglyplie, 106
sipuucle, 358
skeleton,-Ceph(.]ochorda. 613; Enle
ropiieusta, 609
somatic cells, 44
somatlo mesoderm, 206
sperinalid, 48
spermatocyte, 48
spermatogenesis, 48
spermatogone, 48
spermatophore, 355
epermatozoa, 44, 47
splia'ridia, 574
spimiju-.gjands, 449
splaiichnic mesoderm, 206
splauchnocoel, 610
spongiolin, 72
sporocyst, 140
statohlasi, 261
Slerrula, 6G
Stewart, organs of, 576
stigma, 80
8tigmata,-AracImi(i„. m- Tra
cbejifa. 470; U.ochorda, 682
fitomalod.i'um, 105
etoniodoiim, 218
stone- caual, 536
strobila, 104, 154
subiieurai gland, 623
Sycon, 71
symbiosis, 20, 83
syucerebrum, 379
Tffiuioglossate dentition, 307
tapetum lucidum, 836, 440
telolecithal, 53
teJson, 369
testis, 44
thorax, 488
Tiedemaun's vesicles, 557
tissue. 41
Tornaria, 606
toxiglossate dentition, 308
414; rracheata, 470
tracheal brauchia', 491
trichocyst, 35
trivium, 572, 584
Trochophore, 213
trophopolyp, 85, 91
tube-feet, 587
tympanal organ, 498
iyphlosole, 220, 623
Veliger, 320
vehjm, 81, 820, 612
ventral plate, 226
vibnicula. 263
vitellarium, 180, 155, 193
Waler-vascular system, 685
wax-glands, 490
wings, 489, 623
Zo9a, 420
zorecium. 255
zooxanthellte, 20