THE MECHANISM OF SEX-DETERMINATION 61 



Both parents have contributed to its formation. It is 

 not going far from the evidence to infer that the hybrid 

 character is due to both sets of chromosomes being 

 present in all of the cells. 



Fig. 34. — 1. The chromosomes of the egg lie in the equator of the 

 spindle, the chromosomes of the sperm lie at one side. 2. A later stage, 

 showing all the paternal chromosomes passing to one pole. 3 (to the right). 

 A later stage, a condition like the last. There is also a supernumerary sperm 

 in the egg (to left, in another section.) 4. Same condition as last. 5. Plu- 

 teus larva that is purely maternal on one side and hybrid on the other. 

 (After Herbst.) 



The evidence that Herbst has brought forward is of 

 a somewhat different kind. It supplements Baltzer's 

 evidence and makes more probable the view that the 

 chromosomes are essential for the development of the 

 characters of the individual. 



