GERM CELLS IN THE ARTHROPOD A 155 



tion. This may now be recognized as the " nucleolo " 

 of Silvestri or the keimbahn-chromatin as we have 

 decided to call it. 



The spindle at first lies nearer the anterior than 

 the posterior part of the oocyte. As it shortens 

 and condenses it is more often found below the middle 

 of the cell, and finally reaches a position near the 

 posterior end. The conclusion is thus reached that 

 the *' nucleolo" of Silvestri is not a plasmosome 

 (metanucleolus) which escapes from the oocyte 

 nucleus, but consists of all of the chromatin of this 

 nucleus condensed into a more or less spherical body 

 during a peculiar process of spindle formation. 



The discovery of the origin and nature of the keim- 

 bahn-chromatin brought forth a new problem, 

 namely, that of the origin of the egg nucleus. It 

 was early noted that the oocytes containing this 

 peculiar spindle were free from any other inclusions 

 in the cytoplasm. How then do they acquire a 

 nucleus? Two hypotheses have been considered, 

 one of which has a considerable body of evidence in 

 its support. In the first place the nucleus might 

 arise from chromatin granules which break away from 

 the chromosomes during the formation or conden- 

 sation of the spindle. There is, however, no evidence 

 for this view, since the entire chromatin content of 

 the oocyte nucleus seems to take part in the forma- 

 tion of the spindle and later the keimbahn-chromatin. 

 The second hypothesis was suggested when a number 

 of cases were discovered of two oocytes lying end 

 to end without any intervening follicular epithelium. 



