author's abstract of this paper issued 

 by the bibliographic service, october 5. 



EXPERIMENTAL INDUCTION OF ENDOMIXIS IN 

 PARAMAECIUM AURELIA 



R. T. YOUNG 



University of North Dakota 



THREE PLATES 



Variations from the usual number of both macro- and micro- 

 nuclei in Infusoria have been described by several investigators, 

 Hertwig ('88-'89), Calkins ('04), Popoff ('07, '09), etc. Popoff 

 ('09), Sun ('12) and Kasanzeff ('01) have shown that these 

 nuclear changes can be induced by various means (starvation, 

 temperature and chemical treatment). Hertwig (I.e.), Popoff 

 (I.e.) and Sun (I.e.) have pointed out the similarity between 

 these stages and those occurring in conjugation, and the two 

 former authors have compared them to parthenogenesis in the 

 metazoan egg, which can here, as there, be artificially induced 

 (Popoff, '09). This interpretation has been amplified by Wood- 

 ruff and Erdmann ('14, '16) and accepted by Calkins ('15), al- 

 though the former writers have proposed the term 'endomixis' 

 instead of 'parthenogenesis' for this phenomenon. 



According to these latter writers nuclear re-organization serves 

 to rejuvenate a depressed race. This interpretation seemingly 

 contradicts the work of Jennings ('13), who has shown that con- 

 jugation does not result in rejuvenation, but is to be interpreted 

 as a means of producing bi-parental inheritance and variability 

 in the offspring. 1 



Woodruff and Erdmann (I.e.) have shown further that the 

 occurrence of endomixis does not necessarily accompany a de- 

 pression period (see line III, p. 480). Regarding this irregu- 

 larity the authors state that it "is an exception for which the 

 data afford no adequate explanation." Their graphs (text figs. 



1 See also Mast ('16) in this connection. 



35 



