SEXUAL KEPEOD UCTION. 



?73 



plete loss of motility b)' the female cell (fig. 304). Wlien 

 these differences exist in the sex cells their union is no 

 longer called conjugation, Init fertilization, the acti\-e male 

 cell being said to fertilize the quiescent female cell. 



377. Sex organs. — A further stage in the development of 

 sexuality is reached when the cells producing the sperms or 



Fig. 304. — Differentiation of gametes in some marine alg£. a, like gametes of Ecto- 

 carpus. /', sperm, r, egg of Zanai-diitia . The egg loses its cilia and rounds itself 

 before fertilization which is about to occur in d. i\ sperm, y, egg of Juats. This is 

 the extreme of difference in size in gametes. All magnified equally (about 700 diam.). 

 — After Mubius, 



the eggs are differentiated. The cell or the organ pjroducing 

 the egg has been known by -^-arious names in different groups 

 of plants. An appropriate general name for it, -nithout refer- 

 ence to its structure, is the o^■ary. (See further ^ 335.) 



