256 EDITH PINNEY 



plasmic environment is not enough to bring about this result 

 if the germ plasms are not harmonious. 



3. The relation between abnormal mitotic behavior and abnormal 



development 



In the last three crosses listed above, abnormalities in the * 

 behavior of the chromatin during cell division were common. 

 In the three crosses, Fundulus 9 X Ctenolabrus cf, Menidia 

 9 X Ctenolabrus cf, and Stenotomus 9 X Ctenolabrus cf, 

 there occur various amounts of lagging of the chromosomes 

 during division. In the cross Stenotomus 9 X Ctenolabrus cf, 

 several types of abnormalities in chromosomal behavior were 

 found, including the elimination, fragmentation, and abnormal 

 distribution of chromosomes. One might say that in general 

 the degree of developmental abnormality in these hybrids was 

 det rmined by the degree of abnormality occurring in the be- 

 havior of the chromatin. This leads us to suspect that the cause 

 of the abnormal chromosomal behavior is the real cause of the 

 irregular development. 



One of the puzzling features of hybridization has been the 

 wide range of variability displayed in the development of the 

 individuals of one cross. In regard to this variability in fish 

 hybrids Newman says: 



It may, however, be suggested that the differences in success may 

 be due to physiological differences in the condition of the egg and 

 sperm, for it is probable that in any large number of genn-cells forci- 

 bly stripped from males and females, some of each kind will be in a 

 better condition for development than others. 



There can be very little specificity in the germ cells of teleosts 

 since cross-fertilization is so easily accomplished. Among sea- 

 urchins a greater degree of specificity of the germinal products 

 makes cross-fertilization more difficult. In the latter group 

 surface conditions which permit cross-fertilization may be ob- 

 tained by treating the germ cells artificially (Loeb, '16), or in 

 many cases by merely allowing the eggs to stand in sea-water 

 for a certain length of time, (Hertwig, '85; Tennent, '10). 



