No. 600] EXPERIMENTAL INTEBSEXUALITT 715 



made, prove, of course according to expectation, that the 

 factor M is Mendelian and carried in the X chromosome. 

 All results of F 2 and back crosses agree in this point. 

 But what is [ff] ? Originally I believed that I could 

 prove its Mendelian character too. This was a mistake, 

 produced by the interference of another phenomenon, 

 connected with the wing-color inheritance. The experi- 

 ments made since my first communications prove thus far 

 that the complex |ff| is inherited only through the 

 mother, maternal grandmother, etc., i. e., in the proto- 

 plasm of the egg. 



We are now prepared to consider the production of the 

 intersexual males, thus far omitted in our discussion. A 

 series of them has been produced extending almost to 

 femaleness. They are easily distinguishable from inter- 

 sexual females (a point which is of special interest; one 

 explanation being that factors contained in the Y chromo- 

 some are responsible for it). The intersexual males 

 always exhibit the first of the above-mentioned (foot-note 

 page 713) types in regard to wing coloration, white streaks 

 appearing on the dark wings. While the wings assume 

 more and more the female shape, the dark color becomes 

 confined gradually to the wing venation, and in the ex- 

 tremest types thus far bred only a few brown spots ap- 

 pear upon some veins. All the other characters, like size 

 of abdomen and copulatory organs, change hand in hand 

 with this. But the behavior of the sex glands is not yet 

 clear. In low grades of male inter sexuality the testis 

 always contains some ovarial tissue. 7 But the highest 

 grade intersexual males of almost female exterior con- 

 tained a paired 8 sex gland of somewhat testis character, 

 filled with giant bundles of apyrene spermatozoa, and 

 containing no eggs. 



If we now deduce from our general interpretation how 

 these interesting males might be produced, we realize that 



7 See picture in Poppelbaum's paper. The lower grades of male inter- 

 sexuality are photographed in our papers from 1912 and 1914. Pictures 



8 The ripe testis is an unpaired organ. 



