8 



Scientific Proceedings. 



6 (615) 



Color inheritance in Fundulus hybrids. 

 By FRANK W. BANCROFT. 



[From the Rockfeller Institute for Medical Research.] 



In the hybrids of Fundulus heteroclitus and Fundulus majalis 

 it was found that, in general, wherever the color characters were 

 not concerned with the rate of development, the F. heteroclitus 

 characters were dominant over those of F. majalis. These 

 dominant characters were: 



1 . Red yolk chromatophores large and abundant. 



2. Black yolk chromatophores large and usually polygonal in 

 shape. 



3. An early first crop of head chromatophores is present, in 

 addition to a later crop which is found in both pure species and 

 both hybrids. 



4. There is a row of red chromatophores on the lateral line 

 shortly before and immediately after hatching. As soon as the 

 fish hatch the red chromatophores begin to fade, and within 

 a few days disappear entirely. 



On the other hand, when the characters were concerned with 

 the rate of development, the Mendelian dominance was partly 

 or entirely obscured. These characters were : 



5. In F. heteroclitus there are no or very few black chromato- 

 phores on the lateral line at hatching; but they increase rapidly 

 during the first few days after hatching. In F. majalis there are 

 50 or 60 black lateral line chromatophores at hatching. The 

 hybrids are intermediate. 



6. In F. heteroclitus when the yolk chromatophores first appear 

 they are uniformly distributed over the whole yolk; while in 

 F. majalis they are confined to the hemisphere containing the 

 embryo. The hybrids are intermediate. 



7. Both with respect to time, and with respect to the stage 

 of development of the embryo the yolk chromatophores appear 

 first in F. heteroclitus, next in the F. heteroclitus egg hybrid, next 

 in the F. majalis egg hybrid, and last in the pure F. majalis. 



An apparent case of blended inheritance in the time of the 



