EUPHYCOPHYTA 



27 



Species all the cells give rise to new daughter coenobia but in E. 

 illinoiensis the four anterior cells are much smaller and do not re- 

 produce. In E. indica the daughter colonies undergo inversion 

 before liberation as in Volvox. This marks the first differentiation 

 into a plant soma of purely vegetative cells, such cells dying once 

 the colony has reproduced. It would be of considerable importance 

 if the nature of the stimulus that induces some of the cells to lose 

 their reproductive capacity could be determined. 



Fig. 6 Eudorina elegans. A, vegetative colony. B, transverse 

 section showing structure and protoplasmic connections, a = outer 

 layer, Z)= inner layer of mucilage. C, formation of daughter 

 coenobia. D, E. illinoiensis, showing somatic cells, v. (After Fritsch.) 



Sexual reproduction borders between anisogamy and oogamy, 

 the species being either monoecious or dioecious: in the former 

 case the anterior cells give rise to the antherozoids and the posterior 

 form the ova. In the latter case antheridial plates or plakea con- 

 taining sixty-four spindle-shaped antherozoids are Hberated 

 intact, and only break up after swimming to the female colony 

 where the surrounding walls have already become gelatinous. 

 The zygote remains within the parent colony until it disintegrates 

 and when it germinates it gives rise to a single motile swarmer 

 and what are probably two or three degenerate s warmers. The 

 motile swarmer eventually comes to rest and divides to give a new 

 coenobium. 



