THE ORIGIN OF GYNANDROMORPHS. 17 



different kind from those involved in Drosophila when a half of a single 

 chromosome fails to reach its normal destination. 



EARLIER HYPOTHESES TO EXPLAIN GYNANDROMORPHS. 



Dalla Torre and Friese (1897) and Mehling (1915) have reviewed 

 the earlier attempts to account for gynandromorphs. Donhoff (I860) 

 suggested that gynandromorph bees arose from eggs with two yolks, 

 one of which was fertilized, the other not; one began to form a worker, 

 the other a drone, both fusing into one individual later. A second 

 interpretation based on Dzierzon's theory was also suggested, viz, that 

 the egg contains the male potentiality, the sperm the female poten- 

 tiality. In fertilized eggs the latter influence usually predominates. 

 In the gynandromorph, one of these influences predominates in one 

 region, the other in other regions. In 1861, Wittenhagen suggested 

 that a queen that produces gynandromorphs has reached a higher 

 stage of fertility which causes male parts to arise even after fertiliza- 

 tion. Menzel (1862) made several guesses, such as that delayed fer- 

 tilization of the egg leads to irregular distribution of the mass of the 

 sperm material with consequent disturbance in the development. 

 Later (1864) he suggested that abnormal organization of the oviducts, 

 leading to delay in passing of the egg, interferes with the sperm, so 

 that the egg no longer has the possibility of producing a complete 

 female, except in certain regions of the body. 



Von Siebold (1864) thought that insufficient fertilization is re- 

 sponsible for the appearance of gynandromorphs. He assumed that 

 a definite number of spermatozoa are necessary to produce a female. 

 When from any cause an insufficient number of sperms is present, the 

 egg can not develop a female, or a male, but an intermediate type. 



According to Cockayne (1915, p. 117), Scopoli (1777) suggested 

 that a gynandromorph of Phalcena pini might have arisen through the 

 fusion of two pupae lying in one cocoon. Donhoff' s suggestion (as 

 above) of two yolks in one shell that fused is a somewhat similar view, 

 and Wheeler in 1910 made a like suggestion, viz, that two eggs (fer- 

 tilized?) fused at a very early stage, one a male-producing, the other a 

 female-producing. Such a process will not apply, however, to most 

 of the cases in Drosophila, because the evidence shows that the eggs 

 are normally not of two kinds. The male alone produces two kinds of 

 gametes. The sex-linked characters in hybrid gynandromorphs show 

 very clearly that the results are not due to the fusion of two eggs, 

 but to a different sort of process. In the bee also it appears that there 

 is only one kind of egg, and that the female sex is determined by the 

 fertilization of the egg; the male comes from the unfertilized egg. 



On the other hand, there are several cases in Drosophila which can 

 not be explained by simple chromosomal elimination, but which can 

 be explained on the assumption that the egg had two nuclei. Here 



