THE ORIGIN OF GYNANDROMORPHS. 



9 



Another gynandromorph (obtained by Sturtevant), text-figure 3, 

 came from a mother that had in one second chromosome the genes 

 for C„i and for curved, and in the other the genes for black and for 

 vestigial. She may have had a third chromosome gene for crossing- 

 over. The father was homozygous for black, purple, curved, plexus, 

 speck, all in the second chromosome. Brothers and sisters were as 

 expected; the black curved crossing over was 28 per cent. The fly 

 was black and showed no trace of purple, vestigial, curved, plexus, or 

 speck. It was male on the left side, female on the right, except for 

 head bristles. The genitalia were male. The fly was sterile. Unless 

 the egg were a double cross-over for black vestigial curved, which is 

 unlikely, it contained a 

 black vestigial bearing 

 chromosome. The sperm 

 contained the five sec- 

 ond-chromosome genes. 

 Since the male parts 

 showed none of these sec- 

 ond-chromosome char- 

 acters, except black, 

 although all the rest ex- 

 cept purple might have 

 been visible, it is highly 

 probable that the male 

 parts contained both sec- 

 ond-chromosomes. The 

 result shows at least that 

 the theory of chromo- 

 some elimination is a 

 more probable explana- 

 tion than partial ferti- 

 lization or multiple ferti- 

 lization, and the result 

 would be conclusive if 

 the possibility of double crossing-over were rejected. 



Another case (found by Sturtevant, 4079 C, Oct. 31, 1917) occurred 

 in a cross betweem a male with a normal X chromosome and pure for 

 the second-chromosomal genes for black, purple, and curved, and a 

 forked female that was heterozygous for the second-chromosomal genes 

 for black, purple, and curved. The gynandromorph (plate 1, fig. 3) 

 had a short wing on the left side, but the left foreleg was not male. 

 The abdomen had the male banding and genitalia and contained two 

 testes. No forked bristles were found in any part of the body. Elim- 

 ination of one of the forked-bearing maternal X chromosomes left the 

 wild-type X chromosomes to determine the character of the male parts. 



Text-figure 3. 



