THE ORIGIN OF GYNANDROMORPHS. 23 



male, except the genitalia, which were female. Sections showed an 

 abnormal testis near posterior end. It courted and was courted. 



Sturtevant records observations on three other gynandromorphs 

 tested for sexual behavior: 



"None showed any certain indications of male behavior, but all were 

 vigorously courted by males. Of these three gynandromorphs the external 

 characters were as follows: (A) All female, except one side of the head, 

 which was male; (B) female on one side of the whole body, male on the 

 other side; (C) female, except the genitalia, which were male." 



Duncan describes the behavior of a bilateral gynandromorph. Its 

 mating instincts were found to be indifferent. It was courted by 

 males but would not court females. The gonads were both testes 

 with ripe sperm. In a second gynandromorph, the eyes were female, 

 but the forelegs had sex-combs; one wing was long (female); the ab- 

 domen was male type, but the genitalia were half male, half female. 

 Two ovaries were present. The fly was courted "assiduously" by 

 males but would not mate. A third gynandromorph was without 

 sex-combs on the forelegs, the wings were the same length, but the 

 abdomen was male on one side, female on the other, as were the 

 external genitalia also. Mature sperm were present in both testes. 

 This fly was anteriorly female and posteriorly half male and half 

 female. A normal male courted this gynandromorph when in front, 

 but did not copulate wdth it. 



The gynandromorph drawn in text-figure 34 was tested by one of us 

 (Morgan, T. H., Amer. Nat., 1915, p. 246). One side of the head 

 and thorax is male, the other side female. The abdomen is pig- 

 mented above as in a male and there is a penis below. When put 

 with mature unmated females it did not court them, although it was 

 quite active. 



Attempts to breed from gynandromorphs have been often made. 

 It was not to be expected that those in which the genitalia were mixed 

 would successfully copulate. Those with female abdomen have more 

 often given offspring. Since, as explained elsewhere, the gynandro- 

 morphs with male abdomen would not be expected to be fertile (be- 

 cause the XO combination has been shown to be sterile), the frequent 

 failure to obtain offspring from such males is in accordance with ex- 

 pectation. On the other hand, an occasional fertile male gynandro- 

 morph occurs. In these cases the combination was known or suspected 

 of being XXY, the presence of the Y chromosome making the male 

 (XY) fertile. 



PHOTOTROPISM IN MOSAICS WITH ONE WHITE AND ONE RED EYE. 



On several occasions it has been observed that when a mosaic had 

 one red and one white eye it circled to the red side. This beliavior is 

 expected from observations by McEwen on the light reaction of flies 



