1908] YAM ANOUCHI— SPERMATOGENESIS AND OOGENESIS 161 



ones become situated at the poles of the : 

 peated until there is formed a spermatid 



process 



becomes 



account 



of the last two authors. In regard to tC 

 plast he states that the disappearance of nu 



sperma 



between 



account 



is formed within the interior of the nucle 

 spermatogenous cells up to the spermatid grandmother cell. This 

 body moves to the nuclear membrane and is thrust out into the cyto- 

 plasm. It then lies outside of the nucleus and becomes the function- 

 ing centrosome, dividing to form two centrosomes that separate and 

 occupy the poles of the spindle. After the mitosis that gives rise to 

 the spermatids, the centrosome remains to become the blepharoplast 



of the 



sperm - 



Regarding the origin and structure of the blepharoplast of thallo- 

 ph}1es, Stil^sburgee. (85, 87) expressed the following \dew, chiefly 

 based on his study of the zoospores of Vaucheria, Cladophora, and 

 Oedogonium. In all of these forms, he states, the blepharoplast arises 

 from the outer plasma membrane (Hauischlcht), the nucleus lying 

 close to the plasma membrane at the time when the blepharoplast is 

 formed. Another view, based upon the zoospores of Hydrodictyon, 

 was advanced by Timberlake (89), who found that after nuclear 

 multiplication had ceased, segmentation proceeded until uninucleate 

 masses of protoplasm become separated from one another as zoospores. 

 Then a blepharoplast was formed, lying in contact with the plasma 

 membrane. But before the appearance of the blepharoplast, he adds, 

 a granule may sometimes be observed close to the nucleie and it is 

 possible that this is the first appearance of the blepharoplast- Dax- 

 geard's study (21) on Poljioma also suggests some possible rela- 

 tionship between the blepharoplast and nucleus. In zoospores of 

 this form, he finds that the blepharoplast is situated directly under the 

 plasma membrane and that a delicate threadlike structure extends 

 from it into the c\1:opiasm and sometimes ends at the side of the 

 nucleus in a granule. Bavis (24 a) traced the origin of the blefrfiaro- 



