216 Cytoplasm as Sect of Genetic Properties 



priori necessary and, in addition, useful in view of the fact that 

 a considerable number of geneticists speak rather loosely of cyto- 

 plasmic genes when nothing has been established but a cytoplasmic 

 substrate action in all the cases discussed thus far. If a real plasmon 

 in the sense just defined could be proved to exist, the term "cyto- 

 plasmic genie material" could be used by analogy, but "cytoplasmic 

 genes" would still be an indefensible term, in my opinion. An ob- 

 jection might be made to the distinction of a genuine plasmon from 

 a cytoplasmic substrate on the ground that, just as genie material 

 cannot be imagined without the collaborating cytoplasmic substratum, 

 in the same way no plasmon could exist without collaborating genes. 

 Furthermore, it could be said that it is impossible to prove the 

 existence of a genuine plasmon action because an interaction with 

 genically controlled actions can never be excluded. Both criticisms 

 are to the point in themselves. However, just as we deal in classic 

 genetics with genie control of hereditary traits, evidenced by the 

 criterion of Mendelian inheritance, forgetting about the cytoplasm, 

 we might be able to describe cytoplasmic heredity proper as the 

 result of traits which are inherited purely maternally and do not 

 exhibit any effects of different genie constitution. If, for example, 

 the form of a leaf were inherited in this way, the form should be 

 essentially, if not completely, the same in all descendants in the 

 maternal line, in Fi, F2, Fn, and in all replacements of chromosomes 

 by those of another form. 



The question then is whether indubitable cases of this type 

 exist. I once believed I had found an example in the sex determination 

 of Lymantria, where the female determiners are inherited strictly 

 maternally, as shown for the degree of intersexuality obtained even 

 in the most complicated multiple crosses, introducing all kinds of 

 chromosomes of different genetic constitution. If A, B, C, D are 

 different races known to have different X-chromosomes in regard to 

 the relative potency of the sex factors, the crosses (female first) 

 A X B, (A X C) X B, (A X B) X (C X D) X (E X F) X B, 

 and so on, all give the same result, depending exclusively upon the 

 female factorial potency of the maternal, grandmaternal (etc.) race 

 A and the male ( X-chromosomal one) of the race B. A special experi- 

 ment seemed to confirm the conclusion ( Goldschmidt, 1934a). But 

 finally I had to realize (Goldschmidt, 1942??) that my original inter- 

 pretation, location of the female determiners within the Y-chromo- 

 some, was the correct one. (I have mentioned the latter fact in 



