408 



EDITH PINNEY 



The best evidence of regular division is obtained from early 

 anaphases. Such a stage is drawn in figure 13, a and b. There 

 is no abnormality. Mitosis ^here is wholly orthodox. Corre- 

 sponding daughter chromosomes on their way to opposite poles 

 can be identified. 



As seen from this figure and figures 14 and 15, Prionotus 

 chromosomes are indistinguishable in a Ctenolabrus egg. The 

 only difference between the two species of elements lies in the 

 probable presence of more hooked-shaped chromosomes in 

 Ctenolabrus, but it has never been determined that shape is 

 a constant feature in fish chromosomes. Figures 16 and 17 are 

 from the cross Prionotus 9 X Ctenolabrus cf . 



SLTAIMARY OF DATA 



The following table presents, in a summarized form, the data 

 for all of the crosses thus far studied. In case of the cross, 

 Menidia 9 X Fundulus cf, the results stated here are those 



