PERIODIC REORGANIZATION IN PARAMAECIUM 485 



Popoff ('07) found in the culture of Stylonychia mytilus, which 

 he bred for three and one-half months, that after three periods 

 of depression had occurred the race finally became extinct during 

 a period of "sehr tiefe Depression." Popoff does not make a 

 distinction between these various depressions, except in regard 

 to their intensity. He records the fact that at these times char- 

 acteristic nuclear changes as well as a tendency to conjugation 

 were in e\'idence though both were most pronounced during the 

 very deep depression. Again, in a culture of Paramaecium cau- 

 datum, the data from which he does not present in as much 

 detail, he found essentially similar depressions a;nd nuclear meta- 

 morphoses. He identifies the deepest periods of depression with 

 those described by Maupas as ''degenerescence senile" by Hert- 

 wig as " physiologischer Tod," and by Calkins as "depression 

 periods." 



In a later study Popoff ('09) stated that he was able to produce, 

 by treatment with various chemical reagents, identical variations 

 in the nuclear apparatus of cultures of Stylonychia mytilus and 

 Paramaecium caudatum, which in turn he considered similar 

 to those observed by Kasanzeff in starved Infusoria. In other 

 words, PopofT concluded that the nuclear phenomena in all his 

 depression periods are exactly the same as those induced by 

 starvation, chemical stimuli, etc., and further that they cannot 

 be distinguished from those which occur at the onset of normal 

 conjugation. In text figure 21 (Popoff's fig. 25, pi. 2) is shown 

 an animal with two micronuclei in mitosis from a culture of 

 Paramaecium caudatum which Popoff had treated with ammo- 

 nium. This specimen we would interpret as an early 'reduction' 

 division in the reorganization process under discussion. 



We have found that it is possible to retard or hasten the 

 occurrence of the process by the character of the culture medium ; 

 for example, it may occur a few days earlier in animals not 

 supplied daily with fresh culture fluid than in the regular lines. 

 Consequently we can readily believe that treatment with the 

 reagents employed by Popoff would influence its onset. Popoff 

 figures specimens of Stylonychia mytilus in periods of depression 

 and also after chemical treatment which he interprets as showing 



