Conclusions and Theoretical 239 



temperature action upon the eggs. Here is a body of facts, hardly 

 analyzed in respect of our problem, which show definite cytoplasmic 

 control of nuclear behavior; but this control can hardly be called 

 cytoplasmic heredity, much less one by plasmagenes. 



CONCLUSIONS AND 

 THEORETICAL 



The views on cytoplasmic heredity have been in constant flux since 

 Correns brought up the subject in early Mendelian days. For a long 

 time biologists talked about the monopoly of the nucleus, which meant 

 that the cytoplasm is only the place in which the genie material of 

 the nucleus acts. When cases became known in which the specific 

 cytoplasm affected the results of genically controlled actions, the 

 cytoplasm was endowed with hereditary properties. Correns already 

 had developed some general ideas on this subject in 1900. He assumed 

 that the cytoplasm contains a mechanism (an unfortunate term be- 

 cause a chemical condition was meant) which is necessary for genie 

 action. During development these mechanisms are sorted out and the 

 different genes act only upon the proper ones. This mechanism 

 (chemism) is specific for the species. This is a somewhat awkward 

 statement of ideas on genie action in development (we shall later 

 discuss them in detail), which are based upon the facts of experi- 

 mental embryology. 



When cases of specific cytoplasmic action were later found, the 

 idea of a kind of substrate action of the cytoplasm as a whole gained 

 ground; it found its expression especially in Wettstein's concept of 

 the plasmon, and in Strasburger's idea of the idiocytoplasm. At about 

 the same time, when Goldschmidt ( 1924 ) presented the first case of 

 cytoplasmic effect upon gene-controlled characters in animals, Winkler 



