84 



FIRST LESSONS IN ZOOLOGY. 



There are over a thousand species of shrimps, prawns, 

 crayfish and their allies, which agree with the lobster in the 

 most important respects; hence this animal is an example 

 or type of Crustaceans in general. 



Now, how does the lobster see and hear? Its eyes are 

 not, like ours, single and separate, but each eye is com- 

 posed of hundreds, nay, thousands, of simple eyes. Fig. 81. 

 S, represents four of these simple eyes, which are united 



FIG. 89. Common Shore-crab, Cancer irroratus. (Natural size.) 



like a bundle of rods, to form a composite eye. With its 

 eyes mounted on two long stalks, there is little doubt but 

 that the lobster sees well enough to answer its own needs. 

 It also hears well. The lobster's ears are seated in the base 

 of the smaller or first antennas; they may be detected by a 

 clear, oval space on the upper side. On laying this open, a 

 large capsule will be discovered; inside of this capsule is a 

 projecting ridge covered with fine hairs, each of which con- 

 tains a minute branch of the auditory nerve. The sac is 



