ANATOMY OF THE LOBSTER. 



81 



thirteen pairs of cephalo -thoracic appendages, indicating that there 

 are thirteen corresponding segments; these, witli 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'). In the 

 second or larger antennaa are situated the openings of the ducts (Fig. 

 94, li) 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- 



tilO 



Fig. 96. — A^ first maxilla of lobster; en, endopodite; bp. basipodite; flab^ flabel- 

 lum. B, second maxilla of lobster; bp, basipodite (epignathus); cxp, 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 strncture 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; e, eyes; r, rostrum; a^, first pair of aDtenngs; a», second 

 pair; h, outlet of green gland; m, mandible, andp, its palpus; mx, first max- 

 illa; «i^, second maxilla; vip, first maxillipede; mp'^, second maxillipede; 

 vip^, third maxillipede; with ep, epipodite, and g, gill; i-d, first leg; B-(t, six 

 abdominal segments; H, telson; B , first pair abdominal legs of male; B , 

 of female; Z>', section of abdomen, with en, endopodite; ex, exopodite; 6, 

 basipodite; S, section of eye; /, cornea; v, cones; e, rod; n, branches of 

 main optic nerve. 



