82 



THE ORIGIN OF GYNANDROMORPHS. 



or whether, owing to the striking character of their wings, they have 

 more often attracted attention, is perhaps open to question. The dif- 

 ferences between the coloration of the males and females in some 

 species would at once arrest attention. On the other hand, in certain 

 species and in certain hybrid combinations the number of gynandro- 

 morphs is so great that there can be little doubt that their occurrence 

 here is directly related to the specific or to the hybrid nature of the 

 insects. 



Eleven more gynandromorphs of Argynnis paphia added by Wenke 

 brings the total to nearly 1,000. 



In regard to the chromosomal background, the situation is the 

 converse of that in Drosophila and in nearly all other insects. The 

 male has two sex chromosomes (text-fig. 65), which may we call ZZ, 

 and the female one, Z, and another called W, corresponding to the 

 Y of Drosophila. The genetic evidence in the case of Abraxas makes 

 this view highly probable, and Seller has shown in another moth that 

 there is, in fact, such a chro- 

 mosomal difference between wz zz 

 the female and the male. 

 As has been stated, in Dro- 

 sophila the female combina- 

 tion XX is the basis for most 

 of the gynandromorphs be- 

 cause the combination al- 

 lows, through the elimina- 

 tion of one of the X's, the 

 formation of parts with one 

 X which is male. By anal- 

 ogy we should expect in Lepidoptera that the male combination ZZ 

 would furnish the basis for the gynandromorphs of this group, since 

 through elimination of one Z the female condition w^ould arise. 



The most interesting case in the Lepidoptera is tliat of a hybrid 

 gynandromorph in the silkworm moth, because here we know the 

 genetic relation of the factors involved. Toyama obtained two bilateral 

 gynandromorph caterpillars whose mother belonged to a race with a 

 striped ''zebra" pattern in the caterpillars and whose father belonged 

 to a race with unicolorous white larvae. Experiments show that in 

 general zebra pattern is dominant to white. Neither is sex-linked. 

 The left female side of the gynandromorph caterpillar was zebra, the 

 right side white. If we attempt to analyze this case on the basis of 

 Boveri's or of Morgan's earlier views — views based on the assumption 

 that one or two nuclei determine male and female respectively — and 

 assuming that, as in the bees, the male parts have one nucleus 

 and the female parts the combined nuclei, then the result confirms 

 Morgan's view and not Boveri's. But this interpretation does not 



wz 



Text-figure 65. 



