THE GAMETES IN PLANTS AND ANIMALS 



337 



159 



differentiation of the motor mechanism from a cell of the usual sort. 

 But in some cases, as in the angiosperms among plants (Figs. 152, 

 153), in Ascaris (Fig. 165), and in the 

 Crustacea (Figs. 168-70) among animals, 

 the male gamete is almost or quite non- 

 motile. Even in such cases, however, 

 it is none the less a highly specialized 

 cell. In the angiosperms among plants 

 a morphologically differentiated cyto- 

 plasmic mechanism is absent, but the 

 history, form, and behavior of the 

 nucleus attest its specialization. In 

 Ascaris (Fig. 165) the peculiar structure 

 of the cell shows that it has departed 

 far from the generalized form of the 

 embryonic cell. In the crustacean sper- 

 matozoa (Koltzoff, 'o6a) the skeletal or 

 supporting structures are extensively 

 developed, but according to Koltzcff 

 ('066, '08), such structures are present 

 in other spermatozoa also. Ballowitz' 

 ('86-'o8) extensive studies of the finer 

 structure of the spermatozoa also 

 demonstrate the morphological com- 

 plexity of these remarkable cells. In 

 the more highly differentiated forms 

 there remains no trace of the ordinary 

 amorphous cytoplasm of the cells from 

 which they arise: all has either under- 

 gone breakdown as a source of energy 

 or has been transformed into the fibrillar 

 or other structures of the spermatozoon. 

 The development of the female 

 gamete follows a very different course, 

 but is none the less a process of spe- 

 cialization and morphological differen- 

 tiation. Figs. 123, 125, 126, and 128 Meves, '99. 



16J 



160 



FIGS. 158-161. Develop- 

 ment of spermatozoon from 

 spermatid in the guinea-pig: 

 Fig. 158, beginning of trans- 

 formation; Fig. 159, beginning 

 of development of tail; Fig. 160, 

 side view after formation of 

 the thin flat head; Fig. 161, 

 mature spermatozoon. From 



