SEXUAL CHARACTERS OF SOME DOMESTIC BIRDS. 47 



as many other characters which are exactly alike in each sex. The 

 sole difference lies in the ovary. Moreover, the genetic factors that 

 are transmitted, if expressed in terms of their somatic results in the 

 absence of the ovary, are the male characters. In this connection it 

 is important to note that the castrated females have always taken the 

 characters of the male of the race to which they belong. This has 

 been particularly noticeable among the cross-bred ducks, where there 

 are several distinct types. In crosses, then, each sex transmits the 

 same set of genes, while the resulting characters are modified by the 

 ovary into the proper female somatic characters. Unfortunately, 

 however, such a simple solution of the breeding problem is not of 

 universal applicability. The presence of the Type II female, together 

 with certain characters, such as mandible color, stands in the way. 

 Here recourse was made to the genetic constitution of the bird to 

 explain their appearance. Attractive as the ovarian-secretion explana- 

 tion may be, it does not entirely do away with the need for an explana- 

 tion of the inheritance of secondary sexual characters. 



The mode of inheritance of the internal secretion is a different thing 

 from the inheritance of secondary sexual characters as such. Obviously 

 it is closely connected (coupled or linked, if you like) with the inheri- 

 tance of sex itself; so closely indeed that the two can not be separated 

 by any means now available. We must for the present treat it as if it 

 were "femaleness," unless the following hypothesis seems more desir- 

 able. The genes for the secretion may be considered to be inherited 

 independently of the sex genes, but just as the Miillerian duct disap- 

 pears in the male, so the mechanism for the production of the secretion 

 may also disappear in this sex. Such a scheme does away with the 

 use of sex-linked inheritance in this connection. 



IS THE FEMALE BIRD A SUPPRESSED HERMAPHRODITE? 



A true hermaphrodite possesses both ovary and testes with their 

 respective products, ova and spermatozoa. There is no direct evidence, 

 then, that the female fowl is a potential true hermaphrodite, since sper- 

 matozoa have not yet been observed in castrated females. However, 

 the presence of certain accessory organs of reproduction following 

 ovariotomy points strongly in this direction. The anlagen of both vas 

 deferens and oviduct occur in each sex, and so each sex might be con- 

 sidered to be a potential hermaphrodite. It is certain, moreover, that 

 the Miillerian duct completely disappears in the male, but apparently 

 the Wolffian duct and body may not always degenerate in the female. 

 There is good evidence from breeding that the female is a sex hetero- 

 zygote, though the cytological evidence in this respect is negative, 

 resting on the failure of Boring's and Pearl's work to substantiate 

 Guyer's report of an accessory chromosone (sex heterozygotism) in the 

 male. Though in many instances there is indisputable evidence that 

 sex is determined at the moment of fertilization, there is other evidence 



