74 Lessons in Zoology. 



He has two eyestalks, longer than the lobster's. He 

 has two pairs of antennas. (Fig. 2, a, the long antennae.) 

 He has one pair of hard mandibles. I think he has just 

 as many moath-parts as the lobster. 



You are right. He has two pairs of little jaws and 

 three pairs of jaw-feet. 



He has one pair of great claws (Fig. 2, c') and four 

 other pairs of walking-legs (Fig. 2, c'-ci). One big claw 

 is larger than the other. 



Moat of the class vill find that the right olaw is larger than the 

 left, beoanse the aperture of most snail-shells ia on the right side, 

 and this claw is nsed to close it np when the crab is inside. 



The walking-legs are difEerent from the lobster's. The 

 second and third pairs are long and pointed at the end, 

 and the fourth and fifth pairs are short and end in little 

 claws. 



The last two pairs are probably used only for holding 

 the creature in the shell. 



Are there any swimmerets ? 



There are three or four on the left side (Fig. 2, s'-s^), 

 and one pair at the end of the abdomen (s^). 



The male has bat three appendages on the left side of the abdo- 

 men, bnt the female has fonr, which are longer than those of the 

 male becanse used in carrying the eggs. Both have the pair at the 

 end, nsed as claspers. The hard ornst on this pair and on the last 

 two segments of the abdomen, a hard ridge (Fig. 2, r) on the nnder 

 side of the abdomen, and a projection (p) close to it on the left 

 side, all help to hold the orab in his shell. 



In looking for the gills, we trace the flap that covers them np to 

 the side of the body, where it shows beantifnlly that it is nothing 

 bnt a donble fold of skin, thas making clear to teacher, if not to 

 pnpils, its real stracture in the lobster. 



One can hardly find stronger proof than in the hermit-crab that 

 an animal becomes adapted to its snrronndingB, and also that parts 

 uDused will either disappear or so far degenerate as to be incapable 

 of ase. 



