CYTOPLASM AND ACTIVATION OF THE GENE 279 



in the species crosses of Epilobium, pollen fertility is decreased 

 by cytoplasmic influence and, further, that a comparable case of 

 male sterility in flax, studied by Gairdner (1929), and another 

 in Aquilegia (Skalinska, 1928), found also its only probable 

 explanation (given by Chittenden and Pellew, 1927) in the 

 assumption of cytoplasmic inhibition of male differentiation. 



In animals, also, the same problem reappears, viz., in Lyman- 

 tria, but it is much more complicated. The basic fact is that sex 

 is determined by a quantitative relation between female and 

 male determining factors. The male factors are genes situated 

 within the X-chromosomes. The female factor, i.e., the some- 

 thing that carries sex toward the female side, is inherited purely 

 maternally, as is proved by the immense body of experiments on 

 intersexuality. In ordinary crosses, it could be shown that this 

 maternally inherited female factor is not changed in 10 and more 

 generations, and the same is also true when long lines of complex 

 crosses are made, introducing from the paternal side the chromo- 

 somes of many different sex races over many generations but 

 leaving the maternal line untouched. The purely maternal 

 inheritance of the factor controlling femaleness is therefore an 

 experimental fact, which has stood more decisive tests than 

 required. Now, in moths the female is the heterogametic sex, 

 so that maternal inheritance may mean either cytoplasmic 

 inheritance or inheritance in the Y-chromosome. Certain 

 genetic facts seemed actually to favor a location within the 

 Y-chromosome. 



Later, however, very elaborate experiments (Goldschmidt, 

 1934c) proved that actually the property called femaleness is 

 inherited through the cytoplasm. But this property was found 

 to differ in different races in a strictly quantitative way. The 

 differences were called the different types of strength of the female 

 determiners. 



The proof that this property is inherited within the cytoplasm 

 forces one either to assume cytoplasmic genes, which is improba- 

 ble, or to attribute to the specific condition of the cytoplasm a 

 specific influence upon the action of the sex-determining genes. 

 Goldschmidt (1934c), following a similar suggestion by Dobzhan- 

 sky, assumed that the cytoplasmic property, which shifts the 

 balance toward femaleness, is something that controls the level 

 of the threshold for the action of male determining genes. This 



