92 



EAR IN TAIL OF MYSIS. 



possesses a sort of appendage, or languette, to which the 

 nerve is attached. 



As far as details are concerned — the 

 form of the sac, the number, form, and 

 arrangement of the hairs, etc. — the 

 auditory organs of the Crustacea offer 

 endless variations in the different species, 

 while very constant in each. 



In the higher groups the auditory 

 sac is always at the base of the small 

 antennae. In one of the lower forms, 

 however — the curious genus Mysis — 

 the ear is situated in the tail. 



The genus Mysis (Fig. 61) is a group 

 of Crustaceans, in outward appearance 

 very like shrimps, but differing in the 

 absence of external gills, and in the 

 structure of the legs and other par- 

 ticulars, so that it is placed in a different family. Frey 

 and Leuckart, moreover, made the interesting discovery 

 that it possesses two ears in its fail. 



Fig. 60. — Auditory 

 hair of tlie crab 

 {Carcinus mcenus), 

 X 500. a, Skiu ; C, 

 nerve; h, delicate 

 intermediary mem- 

 brane or hinge (after 

 Heusen). 



Fig. 61.— Mysis (after Frey and Leuckart). 



The tail, like that of a lobster, consists of five flaps. 

 In each of the two smaller flaps is an oval sac (Fig. 62) 

 containiug a single, lens-shaped otolithe, consisting of 



