32 A Guide to the Zoological Collections 



higher vertebrates is either absent, or (as in Sharks) is 

 a functional part of the breathing apparatus ; and the 

 bones that correspond with the auditory ossicles of 

 higher vertebrates are in Fishes important parts of the 

 suspensorium of the jaws and hyoid. 



The Muscular System of Fishes is comparatively 

 simple. The eye-balls, the jaws and gill-apparatus, 

 and the fins, all have their own special muscles, but the 

 principal part of the muscular system is massed along 

 the sides of the trunk and tail. Each lateral mass ol 

 muscles is longitudinally divided into a dorsal and 

 ventral band, and each of these again is split up, 

 vertically, into a close-fitting series of conical flakes or 

 segments known as myocommas. 



The Electric ORGANS possessed by certain Fishes 

 are probably peculiar modifications of muscular tissue, 

 by means of which voluntary nervous impulses give 

 rise to powerful electric outbursts instead of to ordinary 

 tetanic contractions. A dissection of one of the elec- 

 tric organs of an Indian Torpedo, or Electric Ray, 

 showing the great nerves that ramify in its substance, 

 is exhibited in Case n. The electric organs are wea- 

 pons of defence and may also be useful in disabling 

 prey. 



The phenomena of Reproduction in Fishes are 

 varied. 



The form and position of the ripe organs of reproduc- 

 tion are shown in the dissection of Trygon and Pristi- 

 ftoma in Case 10, each representing a different type. 



In the majority of Fishes the female lays eggs which 

 are fertilized by the male after their extrusion ; but in 



