Alf ATOMY OF THE LOBSTER, 
81 
thirteen pairs of cephalo thoracic appendages, indicating that there 
are thirteen corresponding segments; these, with the seven abdomi- 
nal segments, indicate that there are twenty segments in a typical 
Crustacean. There is a pair of stalked movable compound eyes. 
The ears are situated in the smaller antennae (Fig. 94, a')- the 
second or larger antennae are situated the openings of the ducts (Fig. 
94, ?() leading from the green glands," while the external openings 
of the oviducts are situated, each on one of the third pair of thoracic 
feet. 
It is impossible, except by counting the appendages themselves, to 
ascertain with certainty the number of segments in the cephalo- 
thorax, the dorsal portion of the segments being more or less obso- 
lete, but the carapace, or shield of the head-thorax, may be seen, 
after close examination, to represent the second antennal and man- 
Fio. 96. — A, first maxilla of lobster; en, endopodite; bp, basipodite; jfZa&, flabel? 
lum. B, second maxilla of lobster; bp, basipodite (epigtiathus); cocp, coxo- 
podite. 
dibular segments, and is so developed as to cover the other segments 
of the head-thorax, the dorsal portions of which are undeveloped. 
To study the internal structure of the lobster, the dorsal 
surface of the carapace and of each abdominal segment 
should be removed; in so doing the soft inner layer of the 
integument is disclosed; it is usually filled with red pig- 
ment cells. The heart lies under the middle of the cara- 
pace; it is an irregular hexagonal mass surrounded by a 
thin membrane (pericardium) with six valvular openings 
Fig. 94.—^, carapace; £, eyes; r, rostrum; a^, first pair of antennae; a^, second 
pair; h, outlet of green gland; m, mandible, and jo, its palpus; mx, first max- 
illa; m^, second maxilla; mp, first maxillipede; mp"^, second maxillipede; 
mp^, third maxillipede; with ep, epipodite, and g, gill; z-d, first leg; B-G, six 
abdominal segments; H, telson ; B , first pair abdominal legs of male ; B , 
of female; D', section of abdomen, with en, endopodite; ex, exopodite; b. 
basipodite; -S*, section of eye; /, cornea; v, cones; e, rod; n, bri.nches of 
main optic ^Qrve. 
