C. Do BELL 145 



Stylonychia in water containing CO.j and Paramecium in water 

 containing ammonia. In both he observed increase in the size of 

 the meganucleus, followed by its fragmentation, multiplication of the 

 micronucleus, and loss of power to divide or assimilate food. The 

 nuclear changes are compared with those occurring during conjugation, 

 but the animals treated in this manner never conjugated. Similar 

 effects were not produced by other chemicals (NaCl, MgCL, MgSOj, 

 glucose). Popoff interprets these results as indicating that katabolic 

 products accumulate during a depression period and cause a disorganized 

 condition of the organism which can be corrected by conjugation and 

 its concomitant reorganization (§ 31). 



35. Results similar to those of Popoff (§ 34) have been obtained 

 with Paramecium by Sun (1912), by adding uric acid or calcium 

 phosphates to the culture liquids. 



36. Gregory (1909) has kept a line of Tillina, magna for 548 

 generations'. "Depression periods" were observed, but chemical 

 stimulation had little effect — " rejuvenation took place, but only to 

 a slight degree." The culture finally died, without conjugation 

 occurring. Gregory interprets her results in the same terms as 

 Calkins (§ 28). She denies that the relative size of the meganucleus 

 increases during depression : but the conclusion appears to rest upon 

 the use of a fallacious " coefficient," and it appears from the few measure- 

 ments given that her results do not really contradict Popoff's (| 32). 

 Moody (1912) has obtained closely similar results with Spathiditnn, 

 which she cultivated for 218 generations. Death, however, was prob- 

 ably due to " abnormal conditions of the environment." She also 

 denies that the size of the nucleus increases during depression, but 

 her measurements do not bear this out. She employs the same 

 peculiar " coefficient " as Gregory-. Calkins, it may be added, has 

 succeeded in keeping Blepharism.a for 224 generations, and Actinoholus 

 for 446 generations. Both lines then died. (See Calkins and Gregory, 

 1913.) 



37. The most extensive work on the duration of the asexual period 

 has been done by Woodruff. Woodruff's earliest work (1905) was on 

 the hypotrichous forms Oxytricha, Pleurotricha, and Gastrostyla — the 



' This organism divides into 2 or 4 daughter-individuals inside a temporary cyst. In 

 one place (p. 399) the number of generations is given as 546. 



- The statistics given for Actinoholus (Table 5) are to me absolutely unintelligible. 

 The volume of the cytoplasm is given in every case as less than that of the nucleus (which 

 is inconceivable) ; yet the average ratio of nucleus to cytoplasm is found to be 1 : 20. 



