NATURAL HISTORY OF AMERICAN LOBSTER. 
223 
great che'iipeas and the first pair of swimmerets. The complex and varied relations 
of the successive somites and appendages of the lobster in the larval and adult state are 
outlined in table 4. 
In their type form (fig. 2 and pi. xxxvi, fig. 5) the appendages consist of an inner 
and outer branch borne on a basal stem, known respectively as endopodite, exopodite, 
and protopodite. The protopodite is composed of two segments, a proximal coxa, or 
coxopodite, and distal basis or basipodite. The coxa of each limb from the maxillae to 
the fourth pair of pereiopods (somites v-xiii) bears a hairy respiratory plate or epipodite, 
from which rises a gill or podobranchia on all but the first two of these somites. The 
primitive type of crustacean limb was probably biramous, since in the course of develop- 
ment we frequently find the uniramous condition produced by loss of the more transi- 
tory exopodite, and further, since the foliaceous form of appendage of the lower branehio- 
pod Crustacea is secondarily assumed by certain of the mouth parts of the lobster and 
other decapods. The undivided form of limb is permanently preserved in metameres 1 
and x-xv, in the last of which the appendage is modified in the two sexes to perform 
distinct functions. The origin of the two-branched antennules will be considered 
presently. The exopodite is frequently abortive, or multiarticulate and elastic, as in 
the swimmeret, a condition which the endopodite has also preeminently assumed in 
the long whips of the antennae. 
with their Chief Functions and Modifications in Larva and Adult. 
Relation of appendage to type form. 
Relation of adult to embryonic and larval ap- 
pendage. 
Apertures of body. 
Doubtful; stalk in two segments 
Doubtful. Basal segment lodges statocyst sac. . . 
Exopodite wanting; exopodite reduced to scale, 
and endopodite irregularly segmented. 
Biramous; two distal segments of palp supposed 
to represent the endopodite. 
Transitory ocellus in first larva; compound eye 
relatively large, and stalks short. 
Bifid, and later uniramous in embryo; finally bi- 
ramous in first larva; inner flagellum a secondary 
outgrowth from primary stalk. Prostomial. 
Bifid, and later completely biramous in embryo; 
poststomial in origin, but later advance in front 
of mouth. 
Body and palp at comparatively late embryonic 
stage. 
Pore of statocyst on up- 
per surface of basal 
segment. 
Papilla for opening of 
renal organ on coxa. 
Mouth, screened by 
labru'm, between 
mandibles. 
Foliaceous; exopodite wanting; endopodite of 
two modified segments. 
Biramous and foliaceous; respiratory fan formed 
by fusion of exopodite and epipodite. 
Biramous and foliaceous, and like maxillae, with 
protopodite modified for testing and passing 
the food. Endopodite 2-jointed. 
In type form; endopodite 5-jointed, and epipo- 
dite with rudimentary gill. 
In type form, modified for mastication, and 
cleaning; second and third podomeres fused, 
and exopodite reduced. Epipodite with func- 
tional podobranchia in ix-xiu. 
Uniramous through loss of exopodite in fourth 
stage. Second and third podomeres modified 
for autotomy, and fused “breaking joint” be- 
tween them. 
Uniramous through loss of exopodite in fourth 
stage. 
Early larval condition similar to adult, but endo- 
podite unsegmented. 
First larval condition similar to adult 
The same, but epipodite without fold for “bailer ” . 
First larval state similar to adult 
In first larva with long swimming exopodite, lost 
at fourth stage, and third joint free; no cleaning 
brushes, and no teeth on ischium. 
Biramous to fourth stage. Big claws nonprehen- 
sile in first larva; of toothed type in fourth, and 
symmetrical up to sixth or seventh stage. Tor- 
sion of limb completed at fourth stage, after 
which big claws are horizontal, and dactyls face, 
opening toward mid-line of body. 
Swimming exopodite shed at fourth stage 
The same 
The same 
The same, without epipodite and podobranchia. . 
The same 
The same 
The same; torsion of terminal segments away from 
mid-line of body completed at fourth stage, when 
limb is directed backward. 
Oviduct opens on coxa. 
Seminal receptacle. 
Vas deferens opens on 
coxa. 
