142 THE TESTES, BY V. LA VALETTE ST. GEORGE. 



animals, and usually in the centre of the seed-preparing 

 portions of the gland, with structures of characteristic shape 

 the seminal animalcules which were discovered in the 

 discharged semen of man by Johann Ham, of Arnhem,* and 

 since then frequently described under the different names of 

 Spermatozoa, Spermatozoids, Spermatoidia, and Zoosperms. 



These constitute the male element of the generative process ; 

 they are constant only in each species, but otherwise present 

 great variety of form in the animal kingdom. 



PROTOZOA. Spermatozoa have been already shown to be 

 present in all forms of animal life. They even exist amongst 

 the Infusoria. In these they were first described by Johann 

 Miiller as thread-like bodies in the Paramecium aurelia, 

 occupying the interior of the enlarged nucleus, and have 

 subsequently been further examined by Claparede, Lachmann, 

 Lieberkiihn, Balbiani, and Stein. 



In the Sponges (Spongilla) Lieberkiihn discovered zoosperm- 

 like corpuscles consisting of an oval head and a thread-like 

 body. 



CCELENTERATA. The spermatoza of the coelenterata possess 

 a round or elongated head, with thread-like body Actinia 

 Hydra, Chrysaora, Eudoxia, Ekizostoma, Athorybia (v. 

 Siebold, Kolliker, Heine, Busch, Gegenbaur). 



ECHINODERMATA. A very similar form is found amongst the 

 Echinodermata, viz., a spheroidal body, with a fine hair-like 

 tail Holothuria, Spatangus, Echinus, Asteracanthion (Valen- 

 tin, Peters, Kolliker). 



VERMES. This class presents great variety in the form of 

 the spermatozoa; whilst the Cestodes and Trematodes (v. Siebold, 

 Kolliker), with the Turbellaria (Max Schultze) possess 

 capilliform spermatozoa, we meet in the Nematode worms 

 with very peculiar structures, the shape of a rod or club 

 (Reichert, Schneider, Meissner, Claparede). Schneider observed 

 amoeboid movements in them. According to Max Miiller, 



* Halbertsma, Archivfur die Holland. Beitrage, 1866, p. 232. 



