STUDIES ON THE LIFE-HISTORY OF PROTOZOA. 



Ill, THE SIX HUNDRED AND TWENTIETH 



GENERATION OF PARAMCECIUM 



I 



CAUDATUM. 1 



GARY N. CALKINS. 



Over 65 years ago, Ehrenberg came to the conclusion that the 

 Protozoa are potentially immortal. Having all of the necessary 

 organs and losing nothing in reproduction, there was no reason 

 at all, he argued, why they can not live indefinitely. Shortly 

 after this, Dujardin published a work in which he stated that 

 Protozoa have periods of activity alternating with periods of rest, 

 and Ehrenberg's view was vigorously contested. 



Among contemporaneous biologists, the matter has been taken 

 up, on the one hand, by Weismann and his followers, on the 

 other by Maupas and those who see in Maupas' work the best 

 weapon with which to combat Weismann. The matter at issue 

 involves an interesting question, viz., will protoplasm having every 

 opportunity to exercise its various activities, and without being 

 specialized through differentiation to the performance of limited 

 functions, continue to live indefinitely, or will it gradually be- 

 come exhausted and die as do the multicellular animals ? Weis- 

 mann, following the line of reasoning pointed out by Ehrenberg, 

 maintains the former point of view, while Maupas, on the other 

 hand, upholds the latter and argues, that, as the race becomes 

 older, the vitality becomes more and more reduced, until finally, 

 the Protozoon, like the Metazoon, dies from old age. Both 

 writers have had to take into consideration the factor of conjuga- 

 tion with the accompanying phenomena which were almost en- 

 tirely unknown to the earlier controversialists. With Weismann, 

 conjugation is merely one of the vital functions of protoplasm, to 

 be considered in the same light as feeding or excreting and not 

 in any way interfering with the theory of immortality. Maupas 



1 A lecture delivered at the Marine Biological Laboratory, Woods Holl, Mass., 

 July 28, 1902. 



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