SEX UA L RE PR OD UCTION. 



273 



plete loss of motility by the female cell (fig. 304). When 

 these differences exist in the sex cells their union is no 

 longer called conjugation, but fertilization, the active 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 algae, a, like gametes of Ecto- 

 carpus. b, sperm, c, egg of Zanardinia. The egg loses its cilia and rounds itself 

 before fertilization which is about to occur in d. e, sperm, /, egg of Fucus. This is 

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

 —After Mobius. 



the eggs are differentiated. The cell or the organ producing 

 the egg has been known by various names in different groups 

 of plants. An appropriate general name for it, without refer- 

 ence to its structure, is the ovary. (See further ^[ 335.) 



