FORMS OF THE SPERMATOZOA. 147 



is highly remarkable. One form is short, and twisted like a 

 corkscrew at its upper end, whilst the other is larger, and 

 presents a rod-like form. From the thicker end of the latter 

 springs a brush of short fibres. 



The spermatozoa of the HETEROPODA consist of elongated 

 and anteriorly rather thickened bodies, while posteriorly they 

 run out into fibres that gradually become more and more 

 attenuated Atlanta carinaria (Milne-Edwards, Gegenbaur). 



In the CEPHALOPODA the zooids are cylindrical, with a deli- 

 cate capilliform appendage Loligo, Sepia, Sepiola (v: Siebold, 

 Milne-Edwards, Peters); or they form hair-like structures 

 Octopus (Philippi). 



PISCES. The spermatozoa of Amphioxus, according to 

 Kolliker, are thread-like bodies with roundish heads, and those 

 of the Petromyzidce are rod or egg-shaped, as- in Petromy:on 

 fluviatilis, and marinus (Ecker, J. Miiller). The spermatozoa of 

 the Osseous Fishes in general have very small pin-shaped bodies 

 Perca, Cyprinus (Wagner, Kolliker). In Cobitis there is a 

 second enlargement below the head (Wagner, Ecker). Those of 

 the Salmonidce have an elongated head, pointed anteriorly so 

 as to resemble the heart on playing-cards, and consisting of 

 two parts, separated from one another- by a slight groove 

 (Owsjannikow). 



The seminal corpuscles of Sharks and Rays are far larger, 

 and are provided with a fusiform and frequently spirally 

 twisted head Squalus, Torpedo, Maia (Wagner, Ecker, v. la 

 Valette St. George). 



AMPHIBIA. The spermatozoa of the Tritons and Salamander 

 are very remarkable objects, and have been the subject of 

 careful investigation (v. Siebold, Czermak). The fusiform head 

 is continuous with a long thread, to the margin of which an 

 undulating border is attached like a frill. 



In Pelobates the head is very long and spirally twisted 

 (Wagner, Leuckart). 



The seminal elements of Bombinator are fusiform in shape. 

 As in the Salamander, a delicate undulating membrane is 

 attached to the sides of their bodies (Wagner, Leuckart, v. 

 Siebold). 



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