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THE AMEBIC AN NATURALIST [Vol. L 



sent a definite step between the two sexes. 2 The phe- 

 nomenon shall therefore be called intersexuality. Further 

 experiments now proved that intersexuality segregates, 

 F 2 giving normal and intersexual animals. It was 

 further shown that in some experiments the females re- 

 mained normal and the males became intersexual. When 

 the experiments were repeated, however, different results 

 appeared. And as the material used came from different 

 strains, suspicion arose that there are many different 

 races of gipsies, differing in regard to those things which 

 are responsible for the intersexuality. This suspicion 

 was strengthened when it became probable that the pecu- 

 liar thing responsible for intersexuality could be influenced 

 by external conditions. If this is the case, conditions in 

 Japan ought to be very favorable for an origin of such 

 racial variation, as the Japanese islands show climatic 

 conditions varying from an almost arctic to an almost 

 tropical climate. These suppositions turned out to be 

 correct, as was proved by the further study of these ques- 

 tions in Japan in 1914 and with the material brought 

 from there to this country. 



In order to make the results clearer and their bearing 

 on the sex-problem more evident, I want to apply just 

 the opposite method from that used in the research work, 

 and to give first the general interpretation of the results, 

 which differs only in a few points from that used since 

 1911, and then the experimental facts from which it has 

 been derived. What we have to explain is that two 

 nearly related forms, both normal in regard to sex-in- 

 heritance, produce, if crossed in one direction, normal 

 offspring, in the other direction, normal males and inter- 

 sexual females; (2) that, as we may now say, the degree 

 of intersexuality is definite in a given cross, but different 

 in different crosses; (3) that intersexuality shows Men- 

 delian segregation; (4) that males may become inter- 

 sexual too in certain crosses. 



The explanation for these and the other facts later to 



2 The special meaning of this will be discussed in another paper in con- 



