MODES OF INHERITANCE IN HYBRIDS 483 



b. The character — three rows of lateral red body chromato- 

 phores of F. diaphanus is dominant over the single row of F. 

 heteroclitus and the total absence of red body chromatophores 

 of F. majalis. But in hybrid between F. majalis 9 X F. dia- 

 phanus cr' these chromatophores though brighter in color than in 

 F. diaphanus are darker than in F. majalis and are larger and 

 more conspicuous than in either parent species. This is a case 

 of what in a previous paper I called hyperdominance. 



c. The character — red chromatophores of forebrain and lips of 

 F. diaphanus and F. heteroclitus is dominant over its absence in 

 F. majalis, but in all crosses in which F. diaphanus is used there 

 is a blending between brown color of F. diaphanus and the 

 bright red of the other two species. 



d. The character — fusion of head chromatophores of F. heter- 

 oclitus is dominant over its absence in the other species, but the 

 degree and extent of the fusion in the hybrids is always less than 

 in the dominant parent. 



2. When a character occurs in both parent species but differs 

 in the degree in which its various attributes express themselves, 

 two alternative modes of inheritance are seen in the hybrids; 

 either there appears a mosaic of the two types, each nearly pure 

 in detail, or each of the units shows an intermediate condition 

 as to the degree in which the various specific attributes find 

 expression. Examples of both of these modes of inheritance are 

 cited as follows: 



a. In hybrids between F. diaphanus and F. heteroclitus both 

 specific types of black head chromatophore appear to be domi- 

 nant and occur side by side — a case of mosiac or particulate 

 inheritance. Each type behaves throughout development like 

 the homologous parental type, for example the F. heteroclitus 

 type fuses with its neighbors to form small masses, while the 

 F. diaphanus type remain as isolated cells. 



h. In crosses between F. heteroclitus and F. majalis there is 

 a blending with respect to the details of both red and black 

 chromatophores wherever these occur. In the hybrids of both 

 reciprocal crosses the individual chromatophores are smaller and 



