THE ALG^E 153 



and are ciliated like them (see Fig. 69, B). They are, 

 however, much smaller, and relatively poorer in 

 chlorophyll. The spermatozoid contains a single 

 nucleus, which is placed near the end opposite to the 

 cilia. These spermatozoids have much more the 

 character of complete cells than those of the higher 

 Cryptogams. In the latter, as we have already seen 

 (p. 116), almost the whole body is of nuclear origin, 

 only the cilia and a very small portion at one end of 

 the body being protoplasmic. In (Edogonium, however 

 (and in the lower Cryptogams generally), the greater part 

 of the body is protoplasmic. The resemblance to the 

 zoospores is a point of the greatest importance, as we 

 shall learn later on (p. 165). 



The female organ, or oogonium, like the antheridium, 

 consists of a single cell (see Figs. 66, 68, and 69), and 

 differs herein from the complex archegonium of the 

 Ferns and Mosses. The oogonium at its first formation 

 is nearly similar to the other cells of the filament. A 

 transverse wall is formed in the usual way ; the upper of 

 the two daughter-cells is the richer in protoplasm, and 

 has the larger nucleus ; this becomes the oogonium ; its 

 lower sister-cell, which is poorer in contents, and has a 

 relatively small nucleus, is the supporting-cell, which in 

 some species, however, may feed itself up, undergo 

 further divisions, and give rise to another oogonium. 

 The oogonium swells out, assuming a round or oval 

 outline, and further increases the amount of its pro- 

 toplasm, so that it encroaches considerably upon the 

 central vacuole. The whole contents meantime with- 

 draw themselves from the wall, and form a free, rounded 

 protoplasmic body the ovum (see Fig. 69, A) in the 

 upper part of which the nucleus is placed. The 



