18 THE ORIGIN OF GYNANDROMORPHS. 



the appeal is made to a binucleated egg in order to account for the 

 distribution of the sex-linked characters, but only indirectly for the 

 sex differences hi the gynandromorph. The different sexes in the 

 two parts are due to fertilization of the two nuclei by male and female 

 producing sperm respectively. The presence of two nuclei in these 

 eggs is easily explained as due to the fusion of two oogonial cells or 

 else by an oogonial nuclear division without cytoplasmic division. 

 The conditions existing at the completion of the last oogonial division 

 are particularly favorable for such a union, for at this stage from a 

 collection of cells (presumably all alike) the most favorably situated 

 turns into the egg and the others into nurse-cells very intimately con- 

 nected with the egg-cell. This view, while similar to Wheeler's, puts 

 a different emphasis on the facts, for here the presence in the eggs of 

 two nuclei does not directly account for the different sex of the parts 

 of the gynandromorph (for this difference is due to the two kinds of 

 sperm that have entered), but explains the distribution of the sex- 

 linked characters in the hybrid gynandromorphs. On the other 

 hand, Wheeler's idea is that two eggs in themselves determined as 

 male and female fuse bodily, i. e., side by side, to give rise to male 

 and female parts respectively. His view would be more nearly realized 

 in the case of moths where the female is the heterozygous sex, and 

 consequently a binucleated condition can be utilized directly to ex- 

 plain not only the difference of sex in the gynandromorph (one nucleus 

 retaining a Z and the other a W chromosome), but also the autosomal 

 mosaics, as in the cases described by Toyama. 



Arnold Lang suggested another possibility in 1912, viz, that an egg 

 that had developed parthenogenetically to the stage when the first 

 two nuclei were formed might be fertilized by a female and a male 

 producing sperm, each sperm uniting with one or the other of the two 

 egg-nuclei. As a result one half should be male, the other half female. 

 The hypothesis will not apply, however, to the bee the forms whose 

 parthenogenetic process of development would seem to best fit such 

 a view because only one kind of sperm is supposed to be produced. 

 Double nuclei should produce female parts. The explanation will 

 also obviously not apply to such cases in Drosophila as those in which 

 the male half shows maternal recessive factors. 



De Meijere (1910-11) has offered certain suggestions concerning 

 the origin of gynandromorphs. He starts from the old idea that each 

 individual, male or female, contains within itself the characters of 

 the opposite sex. He thinks that this holds for the gametes as well 

 as for the somatic cells. Darwin held a similar view and thought 

 that this was true not only for the primary sex-cells (sperm and eggs) 

 but for the secondary sexual characters as well. To-day, however, it 

 is clear that such a statement, at least in regard to the established cases 

 of sex determination by means of sex factors, calls for a more definite 



