124 PHYSIOLOGICAL GENETICS 



by the gene. The (frequently misrepresented) derivation of this 

 viewpoint was as follows. It was found that sex is determined 

 by a balance between male and female sex determiners, one of 

 them (the female one- in byniantria) being constant for both 

 sexes, the other (the male determiners in Lymantria) being car- 

 ried by the X-chromosomes and therefore being present in either 

 one or two quantities. These sex determiners in the X-chromo- 

 some behaved like single genes and were therefore considered as 

 such. Then a series of genie conditions was found, which 

 behaved genetically like a series of multiple allelomorphs of the 

 sex gene and which shifted the balance in an orderly seriation 

 from the value typical for 1 X through all intermediate values 

 to the value characteristic for 2X (the series of intersexes). 

 Since IX or 2X, i.e., one or two sex genes, obviously are two dif- 

 ferent quantities determining the value of the two balanced 

 systems F/M and F/M + M, the series of intermediate values 

 for the series of intersexes obtained in the experiments must 

 represent different quantities of the sex genes between the 

 quantity one (M) and the quantity two (M + M). It is cer- 

 tainly difficult to escape this conclusion, which is independent of 

 the question whether M is one or a group of linked genes. It 

 was strengthened by the proof that all the possible compounds 

 of this series of multiple alleles had exactly the balance values 

 that were expected from the known values of the individual 

 members of the series (measurable by the degree of inter- 

 sexuality, or sex reversal). 



As it was simultaneously shown that these series of sex genes 

 control reactions of definite velocities (see page 52) fit to be 

 arranged in the same orderly way as the balance values, the con- 

 clusion was obvious that it is the quantity of those genes which 

 controls the velocity of the reactions, viz., the production of 

 stuffs controlling sexual differentiation. 



What was up to this point a logical inference from the facts 

 soon was proved to be actually demonstrable. Standfuss (1907, 

 1908), who had produced intersexes in the saturnid moth by a 

 species backcross (at that time not distinguished from gynandro- 

 morphs), realized the correct type of interpretation. After 

 Federley's (1913) demonstration of triploidy in such back- 

 crosses, he noticed that this abnormal number of chromosomes 

 was responsible for the production of these intersexes. (Gold- 



