ANATOMY OF THE LOBSTER. 271 



Though as many images may be formed in each eye as there 

 are distinct crystalline cones, yet, as in man with his two 

 eyes, the effect upon the lobster's mind is probably that of 

 a single image. 



The lobster's ears are seated in the base of the smaller or 

 -first antennae ; 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 contains a minute 

 branch of the auditory nerve. The sac is filled with water, 

 in which are suspended grains of sand which find their way 

 into the capsule. A wave of sound disturbs the grains of 

 sand, the vibrations affect the sensitive hairs, and thus the 

 impression of a sound is telegraphed along the main audi- 

 tory nerve to the brain. 



Organs of touch are the fine hairs fringing the mouth- 

 parts and legs. The seat of the sense of smell in the Crus- 

 tacea is not yet known, but it must be well developed, as 

 nearly all Crustacea are scavengers, living on decaying mat- 

 ter. Crabs also have the power of finding their way back to 

 their original habitat when carried off even for several miles. 



The two large so-called "green glands" situated on each 

 side within the head-thorax, and having an outlet at the 

 base of each of the larger antennae, are probably renal in 

 their functions, corresponding to the kidneys of the verte- 

 brate animals. The shell glands are of the same nature. 



The ovaries and corresponding male glands, are volumi- 

 nous organs, the testes being white, and the ovaries, when the 

 lobster is about to spawn, being highly colored, usually pale 

 green, and the ovarian eggs are quite distinct. The lobster 

 spawns from March till November ; the young are hatched 

 with much of the form of the adult, not passing through a 

 metamorphosis, as in most shrimps and crabs. They swim 

 near the surface until about one inch long, when they re- 

 main at or near the bottom. 



The lobster probably moults but once annually, during the 

 warmer part of the year, after having nearly attained its 

 maturity, and when about to moult, or cast its tegument, tiie 

 carapace splits from its hind edge as far as the base of the 



