200 Cytoplasm as Seat of Genetic Properties 



actions controlling female determination must have taken place in 

 tlie unfertilized egg by way of cytoplasmic predetermination or condi- 

 tioning, which remains active in the once determined way throughout 

 all the development, since it controls (in balance with the X-chromo- 

 somal male factors) all the processes of sexual differentiation. We may 

 safely assume, on the basis of our knowledge of sex hormones in 

 higher forms, that this control exercised by the conditioned cytoplasm 

 is a relatively simple chemical control, and we may derive from this a 

 model for a comparable purely cytoplasmic action. This situation in 

 Lymantria is, by the way, mutatis mutandis, not unique. In Dro- 

 saphila repleta crosses, Sturtevant (1946) described a dominant locus 

 which makes hybrid females intersexual; that is, it has a masculinizing 

 influence which acts only in the unfertilized egg by conditioning of 

 the cytoplasm. In a comparable way, a partially feminizing influence 

 is acting in Drosophila m,elanogaster in the presence of Beaded and 

 Minute mutants with a considerable effect through protoplasmic con- 

 ditioning ( Goldschmidt, 1951fo). 



Some authors (e.g., Ephrussi, 1953) define predetermination as 

 an action of a dominant locus before meiosis, a locus which may be 

 absent after meiosis though the "predetermined" phenotype appears. 

 Such a narrowed definition does not include the really decisive 

 characteristic, the genie action upon the cytoplasm before meiosis. 

 Therefore, any such action is predetermination, as in all the examples 

 just mentioned, regardless of what happens to the respective locus in 

 meiosis. Recessive predetermination is actually the case best analyzed 

 genetically, though a dominant one — for example, the action of the 

 Y-chromosome in the moth egg producing a male, which does not 

 possess a Y after fertilization — is more spectacular. 



The inferences we wish to draw from such cases of typical 

 maternal inheritance, with conditioning of the cytoplasm by genie 

 nuclear factors acting before meiosis, are fortified by the existence of 

 closely comparable facts involving the cytoplasm alone. Oehlkers 

 (1938-1952) has described some very interesting phenomena of 

 intersexuality in Streptocarpus crosses which we shall analyze below 

 and arrive at a somewhat different explanation in detail. I could show 

 (Goldschmidt, 1938^?) that they closely parallel the Lymantria situ- 

 ation so far as the sexual balance and its disturbance in the crosses are 

 based upon a system involving female determiners in the X-chromo- 

 somes (male heterogamety ) and a purely maternally inherited condi- 

 tion, which can be inherited only in the cytoplasm of the egg. The 

 complications involved because of monoecism do not concern us here. 



