THE GENE 



309 



guished by different but typical quantities 

 of the F and M genes. The results are 

 different combinations in which the nor- 

 mal balance as expressed in the above 

 given formulae is disturbed because the 

 quantity of M or F which has been intro- 

 duced into the cross no longer balances 

 the quantity of the other set (F or M), 

 The result is male or female intersexuality 

 of a definite degree up to sex-reversal in 

 both directions, everything occurring in a 

 most orderly way and completely in the 

 hands of the experimenter. The decisive 

 point is then, whether in these experi- 

 ments a real proof has been furnished that 

 the results are produced by the presence of 

 different and typical quantities of the 

 F and M genes. 



There is indeed a very large amount of 

 experimental evidence which consistently 

 leads to the same conclusion. We may 

 mention the fact that such diversified but 

 typical results of a given cross as will 

 be enumerated presently are completely 

 explained and expected members of a 

 series, namely: only males; only females; 

 males normal and females of a definite 

 degree of intersexuality; females and males 

 vice versa; half the females normal, 

 half intersexual; half or another ratio of 

 males intersexual; 3 males: 1 female; 3 

 females: 1 male; the same 2.: 1; only 

 females and a few intersexual males etc. 

 Further, if a given race is crossed in one 

 direction with another test-race we can 

 predict every result of crosses with all 

 other races in every direction. Only this 

 type of circumstantial evidence may be 

 mentioned. But there are also direct 

 proofs of the following types. First: 

 The relative quantities of F and M for 

 different races were determined from 

 experiments on female intersexuality and 

 the races arranged according to the values 

 found. From the very different experi- 

 ments on male intersexuality a similar 



determination was made; the two were 

 always found to coincide. Further: In- 

 dividuals of male gametic constitution 

 (F) MM may be built up in which F comes 

 from a race with high quantities of this 

 gene and both M's from a race with a 

 very small quantity of M. The result is a 

 female in spite of male gametic constitu- 

 tion. We may then build up individuals 

 in which F and one M remain as before but 

 the other M is furnished by a third race of 

 known behavior. The result, namely the 

 production of male intersexes of a definite 

 degree or normal males according to the 

 race which furnishes the M, puts out of 

 question any other explanation; it can 

 only be understood, if really definite and 

 typical quantities of F and M are involved. 

 As a matter of fact any other interpretation 

 of our experiments has never been pro- 

 posed. Moreover it has become still more 

 certain since triploid intersexes have been 

 produced (Standfuss, '14; Bridges, 'zz; 

 Goldschmidt and Pariser, 'Z3; Meisen- 

 heimer, '2.4; Seiler, 'vf) where the differ- 

 ent gene quantities are visibly given in 

 the chromosome sets. (Full discussion in 

 Goldschmidt, 'Z7.) Thus it is claimed as 

 a fact that in our work on intersexuality 

 different quantities of one gene have been 

 studied. 



Now for the effect of these different 

 quantities of genes. It has been demon- 

 strated that intersexuality results if 

 development of the individual proceeds 

 up to a certain point, the turning point, 

 with one sex and is finished after the 

 turning point with the other sex, a 

 demonstration which already has been 

 produced for the intersexes of Bonellia 

 by Baltzer ('14). The degree of inter- 

 sexuality up to complete sex-reversal is 

 determined by the earlier or later position 

 of this turning point. This is not a 

 hypothesis but a fact proved by morpho- 

 logical and embryological study (see 



