PERIODIC REORGANIZATION OF P. CAUDATUM 



81 



In other words the present studies on Paramaecium caudatuni 

 show that most if not all the depression periods of Calkins are un- 

 doubtedly rhythms and the ^cycle' is non-existent — it is merely, 

 as stated above, a rhythm at which the organisms are unable to 

 recover autonomously by endomixis owing to the more or less 

 artificial culture methods imposed in daily isolation pedigreed 

 cultivation (text fig. 7, copied from Calkins, '04). 



It may be well, in view of the recent comments by Hertwig 

 ('14) and by Calkins ('15) in their discussion of our paper on 

 endomixis, to state the position of the problem of depression and 



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Text fig. 7 "History of the A Series from start (Feb. 1, 1901) to finish (Dec. 

 19, 1902) by ten-day periods (three periods to each month). The ordinates rep- 

 resent the average daily rate of division. The heavy dotted lines indicate the 

 limits of the several cj^cles, and the lines of the curve carried to the base indicate 

 that the individuals that were not stimulated by change of diet died out. The 

 points at which such lines leave the curve indicate the time of the successfully 

 changed diet." (Calkins, '04, p. 426.) 



the significance of conjugation in Paramaecium in 1907 when 

 Woodruff began his work on Paramaecium. 



The consensus of opinion of biologists, chiefly on the basis of 

 the work of Maupas, Calkins and Hertwig, was that infusoria 

 are able to reproduce by division for only a limited number of 

 generations, after which protoplasmic old age, depression, and 

 physiological death ensue. For this the sole panacea was 

 conjugation. But Woodruff found that by supplying proper 

 environmental conditions it was possible to breed a pedigreed 

 race of Paramaecium aurelia indefinitely (so far, April 1915, 

 more than 5000 generations) without recourse to conjugation. 

 Therefore, he concluded, in direct opposition to Maupas, Calkins 



