RELATING TO SECONDARY SEXUAL CHARACTERS. 41 



described by Pearl and Curtis, and in another by Shattuck and Selig- 

 mann calls for special comment, since the presence of both testicular 

 and ovarian tissue in the same bird is the essence of hermaphroditism. 

 In general there are two ways of looking at such a result. Either the 

 sex-determining factors have been changed so that in one part of the 

 body, where the reproductive organs are laid down, one condition can 

 prevail, in other parts other conditions; or a mixup of the sex chromo- 

 somes has taken place. Until we get some more evidence concerning 

 such cases it is useless to speculate, although the former view might 

 seem the most probable of the two if the Holland birds of Heir Hou- 

 wink's flock were in a high degree true hermaphrodites. 



But in fact three of the four described by Boring and Pearl were 

 due to tumors of the ovary, which, if they suppress the normal develop- 

 ment of this organ, would be expected to call forth the appearance of 

 the secondary sexual characters of the cock. If the likelihood of 

 developing a tumor were inherited, the frequent occurrence of hen- 

 feathered birds in this flock would be explained. However, one true 

 hermaphrodite in 4 birds is surprisingly high for a chance result, since 

 hermaphrodite birds are very rare. 



The second interpretation suggested above is one that has been 

 advanced and established by genetic evidence in Drosophila, viz, 

 dislocation of the sex chromosomes. In the case of birds the male is 

 supposed to be duplex for the sex factors (ZZ), the female simplex 

 (ZW), and consequently the chromosome-dislocation hypothesis must 

 be worked out contrawise in birds and insects. We should have to 

 suppose that such birds start as males (ZZ), and that at some division 

 of the cells of the embroyo one of the Z's became lost (left at the cell- 

 wall for example) . All the cells that got ZZ would be male; all that got 

 Z would be female. If the reproductive region included cells of these 

 two kinds, an ovotestis would result. The rest of the body should be 

 the same, or nearly so, since the soma of male and female birds is alike 

 whether ZZ or Z, except in so far as it is affected by the secretions from 

 the ovaries (in most races of poultry), or from the testes if the race 

 be Sebright, Campines, or Hamburgs. Birds with ovotestis might, 

 nevertheless, be expected, on this view, to show at times an inter- 

 mediate condition of the secondary sexual characters, according to 

 how much internal secretion is produced in the ovotestis. In other 

 words, the chromosome loss might involve much more extensive 

 regions than the reproduction organs, but show its effects first in that 

 organ and then indirectly other parts of the body be affected by the 

 luteal cells of the testis. There is one rather good piece of evidence 

 that seems opposed to this interpretation. In the hermophrodites the 

 oviduct is present in all cases. Its conspicuous presence in the four 

 hermaphrodites would seem, therefore, to indicate that the birds 



