DEVELOPMENT OF THE GENERATIVE ORGANS. 709 



In the case, however, of the Meroistic egg, where a number 

 of cells unite to form the yelk, such an explanation of the 

 nucleus is inadmissible. Most observers have solved the 

 difficulty, however, by regarding one of the cells as a germ- 

 cell and the remaining cells as yelk-cells. 



If such were the case, it is evident that some difference 

 would be expected to exist between these cells, even from their 

 earliest origin. 



Claus [340] thought he recognised a difference in the nuclei 

 of cells of the young Meroistic ova ; he says : ' The questions, 

 the answers to which are of the highest importance, are 

 whence is the germinal vesicle derived ? and what are its rela- 

 tions to the great yelk-cells ?' He answers these questions as 

 follows : ' I believe my own observations enable me to prove 

 that the epithelial cells, the yelk-forming cells, and the germ- 

 cells are modifications of identical elements.' Which merely 

 means that he found all the cells contained in the youngest 

 parts of the ovarian tubes precisely alike a conclusion already 

 arrived at by numerous observers. Yet Claus believes that 

 in partially formed ova he could distinguish the egg-cell from 

 the rest ' by the smaller size and clearer contents of the 

 nucleus.' 



Mayer [312] thought that each egg contains several germinal 

 vesicles, each making an attempt as it were to form an egg, 

 the lowest only succeeding, and all the others perishing. 



I have examined hundreds of young insect ova to see if 

 there is any difference in the nuclei, and I have entirely failed 

 to find any. Sometimes one, sometimes several, are a little 

 clearer than the rest, but there is no constant difference 

 whatever. 



The terminal chamber of the egg-tubes is usually regarded 

 as a germogen, in which germ ova are developed. Stein [319] 

 appears to have been the first who distinguished the germinal 

 chamber from the rest of the egg-tube and termed it the 

 germ chamber (Keimfach). He regarded the cells in it as free 

 from yelk ; but no one has explained the origin of the yelk- 

 cells, nor the manner in which the germ-cells of the terminal 



