482 H. H. NEWMAN 



4. "The presence of red chromatophores along the lateral line 

 at hatching time or shortly before it (F. heteroclitus condition) 

 is dominant over the absence of red chromatophores at the same 

 time (F. majalis condition)." This is, beyond question, a case 

 of dominance based on the ]3resence of a positive character in 

 one species and its absence in another. Bancroft fails, how- 

 ever, to mention that in the hybrids these red lateral line chro- 

 matophores are smaller and fewer in number than in pure F. 

 heteroclitus. 



To this list of Bancroft's I might add what seem to me to be 

 two other characters as dominant as those just given. These 

 are: 



5. The character — red chromatophores on the head (F. hetero- 

 clitus character) dominant over the absence of red chromato- 

 phores on the head (F. majalis character). These red chroma- 

 tophores are, however, fewer in number and smaller in the 

 hybrids than in pure F. heteroclitus. 



6. The character — fusion of black chromatophores (F. heter- 

 oclitus condition) is dominant over absence of fusion (F. majalis 

 condition). In the hybrids, however, fusion is never so com- 

 plete as in pure F. heteroclitus. 



It is then apparent that no pure dominance is to be found in 

 these hybrids and that partial dominance occurs only in such 

 cases as those cited, in which a character is present in one species 

 and absent in another'. 



3. SUMMARY AND DISCUSSION OF DATA ON PIGMENT INHERITANCE 



1. When a character is present in one species and entirely 

 absent in the other, the hybrids between the two species exhibit 

 dominance of a more or less perfect type. Examples of this 

 type of inheritance are as follows: 



a. The character — one row of lateral line red chromatophores 

 of F. heteroclitus is dominant over the absence of lateral line 

 chromatophores in F. majahs, but the individual chromatophores 

 are smaller and less complexly branched in the hybrids than in 

 F. heteroclitus. 



