CHROMOSOMES IN CROSS-FERTILIZED ECHINOID EGGS. 1 33 



The results of the study may be summarized as follows : 



1. The equatorial plate of the Moira-Toxopneustes cross shows 

 a mixture of two kinds of chromosomes not sufficiently unlike 

 one another to enable a positive distinction between the two. 



2. The equatorial plate of the Moira-Arbacia cross shows a 

 mixture of two kinds of chromosomes, one variety long, the 

 other variety short. These differences in form are correlated 

 with the spermatozoon and the &^^ respectively. 



Bryn Mawr College, 

 March, 1908. 



