THE ORIGIN OF GYNANDROMORPHS. 



the mother contains a mutant gene in one of her autosomes and the 

 father contains its normal allelomorph, it is expected, on Boveri's 

 view, that the male side of the gynandromorph should show this 

 maternal autosomal character, even though recessive. But on the 

 hypothesis of chromosomal elimination, both sides of the gynandro- 

 morph should show the same autosomal characters. Conversely, if 

 the cross is so arranged that a recessive mutant autosomal gene enters 

 from the father's side, then, on Morgan's earlier view of polyspermic 

 fertilization, the male side of the gynandromorph should show this 

 recessive mutant character; but on the elimination hypothesis both 

 sides should show the same (dominant) autosomal characters. It 

 may now be shown by critical examples that the hypothesis of chromo- 

 somal elimination will cover nearly all of the cases of Drosophila, and 

 is therefore preferable to either of the other two, even although in 

 special cases either of these two other ways of producing gynan- 

 dromorphs may be realized. A few additional cases have been found 

 that call for still other interpretations. 



The critical cases are as follows: A yellow white male was mated 

 to a female pure for the recessive autosomal genes for peach eye- 

 color, spineless body, kidney eye-shape, sooty body-color, and rough 

 eyes. A gynandromorph was found (plate 1, fig. 1) that was male 

 on one side, as shown by his shorter wing, sex-comb on the foreleg, 

 and the shorter bristles characteristic of the male (the body was 

 also slightly bent to the smaller male side), and female on the other 

 side, as shown by the converse characters to those just given. The 

 gynandromorph possesses on both sides all of the characters dominant 

 to the five recessive autosomal factors that came in with the sperma- 

 tozoon. On Boveri's explanation, the male side should have a yellow 

 body-color and a white eye, because their two genes are carried by 

 the maternal nucleus, while the female side should show the normal 

 characters of the wild fly, as is the case. The absence of yellow 

 body-color and white eyes on the male side rules out his explanation. 

 On Morgan's hypothesis of polyspermy, the male side that comes 

 from one or more supernumerary sperms should show the five auto- 

 somal recessive characters brought in by each sperm, which is not 

 the case, and the female side should show the normal characters, as 

 it does. The absence of the five recessive characters on the male 

 side rules out this explanation also. On the theory of chromosomal 

 elimination the gynandromorph started as an ordinary XX female 

 one X carrying the genes for yellow and for white, the other carrying 

 their normal allelomorphs, viz, genes for gray and for red. Either of 

 these chromosomes might be the one to be eliminated, i. e. } at some 

 division either one of the yellow white daughter chromosomes failed to 

 reach one of the daughter cells, or one of the gray red daughter chromo- 

 somes failed. If the former, the male side should get only the gray 



