STUDIES ON GERM CELLS 



445 



three types of dispermic eggs described, the cells could be iso- 

 lated in pairs, one AB-cell paired with one Pi-cell, an embryo, 

 normal except in size, would result from each pair. 



Eggs which were strongly centrifuged cut off at the beginning 

 of the first cleavage a granular ball at the heavy pole. This 

 phenomenon was previously reported by Hogue ('10) and such 



Fig. 21 Ascaris (from Boveri, '10b); diagram showing segregation of pri- 

 mordial germ cells. E, egg; Pi, P2, Pz, stem-cells; P4, primordial germ cell; 

 circles represent somatic cells. 



eggs were termed 'Balleier.' In these egg's the two cells of the 

 four-cell stage which are adjacent to the 'Ball' undergo the 

 diminution process; the remaining two are stem-cells which 

 give rise to the germ cells. Thus there are two 'Keimbahnen* 

 proceeding side by side in a single egg and four primordial germ 

 cells are produced instead of two as in normal eggs (see fig. 21). 



