430 



Genetics of Sex Determination 



with two X-chromosomes from the very weak race Hokkaido into the 

 formula F8t(Y)/Mw(X)Mw(X), with st and w representing strong 

 and weak, the resulting individual is a female by sex reversal in spite 

 of possessing two X-chromosomes. By appropriate crosses, genetic 

 males (i.e., with two X's) can be obtained from eggs with the strong 

 Y and one weak Hokkaido M, if the other M(X) is taken from races 

 with ascending strength of M up to the very strong Mgt. (We must 

 keep in mind our discussion on predetermination, in H 2 A, meaning in 

 this case that the Y of an egg to become a male or male intersex al- 

 ready has acted before fertilization.) In figure 23, six such combina- 

 tions are represented. All have the strong F from Tokyo and one very 



Fig. 23. Replacement of very weak Hokkaido determiners by a series of 

 stronger ones and result upon grade of intersexuality in males of Lymantria 

 dispar crosses. (From Goldschmidt, 1938a.) 



weak M from Hokkaido. In addition, the XX individuals have one 

 M(X) from a set of races known from other experiments to contain 

 M's of ascending strength. The perfectly consistent results are given, 

 with the range of variation of each combination. Again quite different 

 groups of autosomes are brought together, for example, in the second 

 combination made by crossing (Tokyo X Hokkaido) $ X Berlin $. 

 Nevertheless, the result is determined only by the Y and the two X's, 

 the latter acting together in a strictly additive way. 



The third proof can be derived from the following fact: if the same 

 weak race Hokkaido as mother is crossed to the strong Tokyo father, 

 all potential female offspring are transformed into males. Occasionally, 

 however, one or a few real females appear. If they were ordinary 

 daughters (owing to a failure of sex reversal for unknown reasons), 



