CYTOPLASM AND ACTIVATION OF THE GENE 277 



solution of the problem will become clear if we turn now to the 

 consideration of a possibility of interpretation that has recently 

 been tried rather successfully. 



We have mentioned before the fact that cases are known in 

 which the genes obviously influence the behavior of the cytoplasm 

 of the egg, e.g., the case of the dextral and sinistral snails. We 

 must consider, therefore, at this point the question whether or 

 not after all the differences of cytoplasmic nature under discus- 

 sion are not themselves the products of genie action. Of course, 

 such a simple relation is out of the question because this would 

 result in a type of inheritance like Toyama's so-called maternal 

 inheritance. But there is also another possibility. Jollos 

 (1921, 1924) has discovered the strange phenomenon of Dauer- 

 modification, in which the action of external conditions changes 

 certain characters of an organism and the change reappears in 

 the next generation in a lesser degree and may continue thus for a 

 number of generations until it finally disappears. A number of 

 such cases in Protozoa and Metazoa are known (see Haemmer- 

 ling's review, 1929), and in all of them the obvious explanation 

 is that the change in question is a cytoplasmic one, which only 

 slowly, in the course of a few generations, is overcome by the 

 action of the genes, controlling the normal cytoplasmic constitu- 

 tion. The experiments designed to test this interpretation have 

 given consistent results (Jollos), though it should be added that 

 all decisive tests have not yet been performed. Jollos and 

 Haemmerling have pointed to the near relation of this body of 

 facts to those reported earlier. If an experimentally induced 

 Dauermodification may need up to 8 or 10 generations to dis- 

 appear, one might conclude that in the previously mentioned 

 experiments of Michaelis and Wettstein no proof is contained that 

 the cytoplasmic difference between the two forms, which was 

 originally present, remains in spite of the presence of foreign 

 genes. It might be quite possible that longer continued experi- 

 ments would show that, just as in Dauermodification the effect 

 of the stimulus disappears in the course of some generations, 

 so the primary, natural plasmatic differences will slowly disappear 

 under the influence of the genes of another form. This would 

 mean that the primary plasmatic differences of subspecies and 

 species would also be controlled by the genie constitution but 

 would be of such a nature that one series of ontogenetic processes 



