402 EDITH PINNEY 



mitotic disturbance was not the cause of all of the abnormalities 

 appearing during the course of development in fish hybrids is 

 quite certain, since hybrid eggs which undergo normal mitosis 

 in early cleavage often fail to develop (12). The cause of the 

 later-appearing derangements still remains to be determined. The 

 two problems are not necessarily identical and the present paper 

 will be limited to a consideration of the abnormal mitoses imme- 

 diately following fertiUzation and their significance. 



In the paper referred to above (15) I suggested that the suc- 

 cess of the first cleavage mitosis depends upon certain specific 

 physical conditions of the substratum, namely, the egg proto- 

 plasm. The new crosses described in this paper strengthen 

 that interpretation and, by extending the field for comparison, 

 throw Hght also, I believe, upon some hitherto rather ob- 

 scure and puzzhng results of fish hybridization. I refer to the 

 absence of any correlation between developmental results and 

 taxonomic relationships. 



For a detailed account of the behavior of the chromatin in 

 the Ctenolabrus crosses with Fundulus heteroclitus, Menidia 

 menidia notata and Stenotomus chrysops, the reader is referred 

 to my earlier paper (15). The methods used in the present 

 investigation are also fully discussed there. I will confine the 

 descriptive part of this paper to new crosses or new observations 

 on previously described crosses. 



I. DESCRIPTION OF CROSSES WITH FUNDULUS 



1. Fundulus heteroclitus 9 X Ctenolabrus adspersusc^ 



This cross was discussed in my earher paper. At that time 

 I had only a few preparations of my own. These taken in con- 

 junction with the figures published by Morris (11) and compared 

 with my own preparations of normal Ctenolabrus eggs, formed 

 the material basis of my conclusions in regard to this cross. 

 In order to clear up any doubt to which the former Hmitations 

 in material might give rise, I wish to report here upon a new 

 lot of preparations which furnish abundant evidence that the 

 Ctenolabrus chromatin in the Fundulus eggs is very unequally 



