268 PHYSIOLOGICAL GENETICS 



skeleton. No influence of the cytoplasm could be found, though 

 it would be difficult to prove it. 



The third method has been introduced by Baltzer (1933) on 

 the basis of old observations by Spemann, producing merogons 

 in Triturus. The Triturus merogons did not grow long enough, 

 however, to permit an analysis of the specific differences. Later, 

 it was shows that merogonic tissues, if transplanted to a normal 

 host, may survive and develop far beyond the stage possible in 

 the pure merogon. This fact has been used recently by Hadorn 

 (1936) to perform an experiment of the type discussed here. The 

 egg of T. palmatus is fertilized by sperm of T. cristatus, and then 

 the female nucleus is removed with a pipette. After gastrulation, 

 a piece of presumptive epidermis is removed and transplanted 

 to a gastrula of T. alpestris. The merogonic epidermis will cover 

 most of the left side of the resulting chimera. This can be bred 

 beyond metamorphosis. The skin of T. palmatus which furnished 

 the plasma of the merogon is characterized by papillae made up 

 of a series of flat cells. The epidermis of the part of the chimera 

 'derived from the merogon shows exactly this structure, i.e., 

 the structure of the species that furnished only the cytoplasm 

 of the merogon. It must be added, however, that the alpestris 

 host produces the same structure. It is therefore possible that 

 the effect has not been produced by the cytoplasm of palmatus 

 but by an induction from the alpestris host, which, however, 

 would be a quite unusual feature (though existing in Aceta- 

 bularia). In any case, the experiment is not convincing enough 

 to derive conclusions upon cytoplasmic inheritance. Very little 

 is known of merogony in plants. East (1934) cites a few cases 

 obtained more or less fortuitously after crossing by Kostoff (1929), 

 Clausen and Goodspeed (1925), Clausen and Lammertz (1929), 

 and Nawaschin (1927), none showing any cytoplasmic influence. 



A second somewhat similar type of experimentation in this field 

 has been performed on cells of fungi by Harder (1927). In 

 Basidiomycetes, a stage occurs after conjugation in which one 

 of the cells contains a mixture of the protoplasm of both parents 

 but only one nucleus. This cell may be isolated and grown. 

 If the two parents belonged to different forms (Schizophyllum 

 commune and Phuliota mutabilis), the influence of the mixed 

 protoplasm as contrasted to the one nucleus could be studied. 

 Some of the hereditary traits showed only the influence of the 



