RESULTS OF HYBRIDIZING RING-DOVES. 3^9 



Dark Brahma X Brown Leghorn. Lacing characters. Daven- 

 port ('12). 



Barred Rock X Langshan, Morgan and Goodale ('12). 



[In the above table I have classed the Silky fowl as recessive 

 to the Brown Leghorn for the peculiar pigmentation which is 

 characteristic of the Silky fowl mesodermal tissues. With this 

 interpretation the case furnishes, in my judgment, a strong argu- 

 ment for the position taken in this paper as it does not seem 

 probable that the pigmentation which appears in FI females is 

 derived from the Brown Leghorn hen.] 



The commonly employed gametic analysis of these phenomena 

 involves the assumption that in such cases, at least, the female 

 is heterozygous for sex and the male homozygous. The female 

 of the dominant form is assumed to be heterozygous also for 

 the somatic characters involved. To various writers it has 

 seemed more feasible to either ignore the opposing cytological 

 evidence with regard to sex determination or to assume that the 

 cytological conditions are different in these forms. Unfortu- 

 nately, cytological evidence is difficult to obtain with birds, 

 though Guyer ('09) has published observations which indicate 

 that the common fowl has two kinds of sperms. 



Other interpretations have been suggested by de Meijere ('n ). 

 who assumes that potentialities of both sexes are present in 

 each gamete. According to de Meijere, one sex gets the upper 

 hand in the egg during fertilization at the expense of the other. 

 Just how this writer conceives of the operation in the phenomena 

 of sex-linked inheritance, is not clear to me. 



In thinking over these phenomena, I have been much im- 

 pressed with the fact that recessive characters appear in FI only 

 when the male parent is recessive, and it is hard to resist form- 

 ing the opinion that the recessive male is responsible for the 

 situation. In the case of the turtle dove genus, whenever a white 

 ring-dove male is crossed with a female blond ring-dove or with 

 a female of Turtur humilis, white female offspring occur in FI. 

 As this paper is going to press, an article by Staples- Browne ('12) 

 has appeared in which crossing experiments with pigeons are 

 described. These include crosses between "Turtle doves" 

 (Turtur turtur} and so-called "White Java Doves" which I infer 



