426 LORANDE LOSS WOODRUFF AND RH. ERDMANN 



in a broad sense, recent studies on these organisms have only- 

 served to emphasize that size and simpUcity do not necessarily 

 go hand in hand and that a unicellular or non-cellular animal 

 with all its varied life processes performed within the confines 

 of a protoplasmic unit presents difficulties which differ in kind 

 rather than in degree from those encountered in the metazoa. 

 No better instance of the truth of this could be presented than 

 that afforded by studies on the life history of the Infusoria. 

 Dujardin's ideas of simplicity — brought forward to combat Ehren- 

 berg's mistaken interpretations of the complexities which he 

 observed — gradually were displaced by the revelations of Bal- 

 biani, Biitschli, Engelmann, Maupas, Hertwig and others on the 

 complicated phenomena of conjugation, while the results of more 

 recent work on conjugation from the standpoint of dynamics 

 and heredity have only served to emphasize the intricacies of 

 the infusorian life processes. The present study fully describes 

 still another complex nuclear phenomenon' which we have dis- 

 covered in the life of Paramaecium aurelia and which we believe 

 affords the key to certain apparent contradictions in recent 

 results on the life history of the Infusoria. 



The problems of protoplasmic senescence and the significance 

 of fertilization have afforded the stimulus for a long series of 

 investigations on the life history of Infusoria since, more than 

 three-quarters of a century ago, the leading students of micro- 

 scopic organisms, Ehrenberg and Dujardin, theorized on the 

 potential immortality of these forms. It remained, however, 

 for Blitschli (76) and Engelmann ('76) to attack the problem 

 experimentally, in the light of zoological advance in the inter- 

 vening years, and to reach the conclusion that continued repro- 

 duction by division results in degeneration and death; while the 

 classic studies by Maupas ('89) on the life history of a number 

 of different species of Infusoria afforded such a wealth of evi- 

 dence pointing in the same direction that conjugation as a sine 



1 We have already given brief outlines of this process in the Proc. of the Society 

 for Exper. Biol, and Med., vol. 11, no. 3, February 18, 1914, and in Biol. Cent., 

 . Bd. 34, 1914. In the latter several errors are present owing to the war prevent- 

 ing a revision of proof. 



