THE BEHAVIOR OF THE CHROMATIN IN HYBRIDS 

 BETWT^EN FUNDULUS AND CTENOLABRUS 



MARGARET MORRIS 



Oi^horn Zoological Laboratory, Yale Unu'ersity 



THIRTY-SIX FIGURES (fIVE PLATES) 



The following investigation was begun in the summer of 1911 

 at the suggestion of Dr. Kellicott of Goucher College, and the 

 material was collected at Woods Hole in the summers of 1912 

 and 1913. I am indebted not only to Dr. Kellicott for the 

 suggestion, but also to the members of the Zoological Faculty 

 of Yale University for the privileges extended to me in the Yale 

 laboratories, and for their advice and encouragement while I 

 was following out the problem. 



Fundulus heteroclitus and the cunner, Ctenolabrus adspersus, 

 are common in the waters about Woods Hole. The spawning 

 season for both kinds of fish is approximately the same, extend- 

 ing from the last of May till the first of July. The eggs are easy 

 to get from both species, and the sperm of Ctenolabrus can be 

 easily expressed. The male Fundulus is more difficult to strip 

 and it is best to tease out the testis in a watch-glass, add a few 

 drops of water, and use this fluid to fertilize the eggs. The 

 Fundulus eggs can be obtained at any time of day, and from 

 females that have been some days in the laboratory; but the 

 Ctenolabrus eggs are not good if taken from a female that has 

 been in the aquarium over night. As the eggs do not ripen till 

 late in the afternoon, it is best to have a fresh supply of Cteno- 

 labrus brought in not earlier than 3 p.m. A few males will prob- 

 able live over night, and their milt can be used for Fundulus eggs 

 the next morning. 



The usual precautions were taken to prevent normal fertili- 

 zation of the eggs; that is, fertilization by the sperm of their 



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