VAUCHERIA. 



95 



it wanders toward the center of the oogonium (Fig. 34, C) , which is now 

 separated from the filament by a cross- wall. The egg-nucleus retains 

 this position until fecundation (Fig. 34, D) ; it does not divide and the 

 probability of any nuclear substance being thrown off with the extru- 

 sion of a small plasmic or mucilaginous mass when the oogonium 

 opens is, therefore, excluded. Although Oltmanns observed in the 

 cytoplasm of the beak granules staining somewhat more intensely than 



"tSS&aJKWsiflBSSSS-- 



B 



FIG. 34. Fecundation in Vaucheria clavata. (After Oltmanns.) 



A, B, young oogonia before being delimited by transverse walls from filament. In B all 

 nuclei save one are passing back into filament. 



C, oogonium ready for fecundation. 



D, the spermatozoid has entered egg. 



E, F, sexual nuclei in contact ; in F the male nucleus has increased in size. 

 G, a fusion nucleus. 



H, oogonium containing oospore several weeks old. 



the rest, yet he does not think it probable that these sustain any rela 

 tion to the nuclei. At the upper end of the egg is the rather large recep- 

 tive spot formed by the withdrawal of the chloroplasts from that region. 

 Immediately on entering the cytoplasm of the egg the sperm-nucleus 

 increases noticeably in size ; its linin net, now more loosely arranged, 

 reveals many strongly-staining granules which are probably chromatin. 

 In the meantime the egg-nucleus enlarges considerably, and appears 



