200 



ORIGIN OF SEX AND OF THE SOMA 



cate threads of cytoplasm (Figs. 27, 28, A-C). V. globator, 

 which is larger and less variable in size, has its cells 

 much closer together and joined to one another by stout 

 angular projections from the cytoplasm of the cell 

 bodies (Fig. 29). It is interesting to note that V. aureus 

 has larger green male gametes (Fig. 28, E), yvhile 

 V. globator has smaller very thin sperms, with the hinder 

 end yellow and the two flagella usually attached about 

 the middle of the body (Fig. 28, F), thus departing 

 much further than the sperms of V. aureus from the 

 structure of the primitive Chlamydomonadine cell, 

 though still showing clear traces of derivation from 

 that structure. The sperms of V. globator are nearly 



Fig. 29. — Vegetative cells of V. globator seen in profile of surface of 

 coenobium. Note cell walls and broad protoplasmic connexions. 

 The cell on the left is a young parthenogonidium. x i,6oo. 



as much reduced and highly specialised as those of 

 green plants very much higher in the scale of vege- 

 tative structure. The extreme contrast between the 

 male and female gametes in size, shape and structure 

 is very obvious (Fig. 28, G), though each may be 

 clearly derived from the Chlamydomonadine cell 

 through the stages of differentiation we have traced. 



Nature and Significance of the DifEerentiation between 

 Male and Female Gametes. — The wide difference in 

 structure and function between the male and female 

 gametes of Volvox globator is repeated in the sexual 

 differentiation of gametes in the vast majority of 

 organisms, including, all the higher forms of hfe, both 



