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THE AMERICAN NATURALIST [Vol. XLIX 



power have a less well developed power of asexual endo- 

 mixis than do lines that are relatively sterile, and this, 

 correlated with their reduced vitality, if conjugation were 

 prevented, would account for the death of all pedigreed 

 races prior to Woodruff's, which, as Woodruff and Erd- 

 mann now show, has a high power of asexual endomixis. 

 We are still justified, I believe, in maintaining the state- 

 ment—modified now by their description of asexual reor- 

 ganization—as quoted by Woodruff and Erdmann: 



Woodruff's Paramecium aurelia is evidently a Paramecium Methuse- 

 lah belonging to a non-conjugating line the life history of which is not 



It is clear that the cycle emphasized by Maupas, Calkins and others 

 is merely a phantom which has continually receded as each successive 

 investigator has approached the problem with improved culture methods 

 until it has vanished with Woodruff's race of (so far) 4,500 generations. 

 What remains then is the rhythm and in the light of the present study, 

 which demonstrates the underlying cytological phenomena of which it 

 is an outward physiological expression, the whole problem takes on a 

 new aspect. The cell automatically reorganizes itself periodically by a 

 process which, in its main features, simulates conjugation — -but without 

 a contribution of nuclear material from another cell. Therefore it is 

 evident (as has been shown by this culture) that the formation of a 



essary for the c.miiniicd life of !ho cell— it has an internal regulating 

 phenomenon which is entirely adequate to keep it indefinitely in a per- 

 fectly normal condition. 12 



Here we are brought up sharply to face the question 

 which every student of pedigreed infusoria since Maupas 

 has tried to solve. Woodruff and Erdmann conclude 

 from their observations that old age and natural death 

 do not occur in Paramecium and that the so-called " cycle' ' 

 is non-existent. I would draw from their observations 

 exactly the opposite conclusions, viz., that the one appar- 

 ent exception among pedigreed races, to the rule of de- 

 pression and natural death in the absence of conjugation 

 or its equivalent, is now removed, and that Woodruff's 

 culture is no more than a long series of cycles. 



