REPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 227 



in April, so that ''all four quadrants are now represented in the 

 conjugating lines." Inasmuch, then, as all the ^quadrants' are 

 now shown by these later results to possess the power of con- 

 jugation, the results of the experiments do not seem to be such 

 as to prove that there are conjugating and non-conjugating 

 races present in these cultures. The explanation as to why some 

 of the 'quadrants' conjugate more freely than others may lie in 

 some external condition or conditions of the environment rather 

 than in any inherent difference in the animals of the various 

 'quadrants/ since, as noted above, my work with Stylonychia 

 pustulata has shown that a 'conjugating race' and a 'non-conju- 

 gating race,' using Calkins' terms, may be obtained from the de- 

 scendants of a single individual not an ex-conjugant by the sub- 

 jection of the different lines to various culture conditions. 



In the experiments recorded in the present paper it has 

 been shown that Oxytricha fallax under certain culture condi- 

 tions, which at the beginning of the work appeared to be entirely 

 suitable, lived about three and one-half months, but that under 

 other culture conditions they lived nearly eight months, or more 

 than twice. as long. In Pleurotricha lanceolata, also, the ability 

 of different culture conditions to vary the life history of the 

 organism hds been clearly shown in that one of the cultures 

 lived 259 days, another lived 478 days, and another gives every 

 promise, after over 22 months of existence, of having culture 

 conditions which are entirely suitable and in which it can live 

 indefinitely without conjugation or artificial stimulation.- 



The graphs showing the division rate of all the daily isolation 

 cultures, of both the organisms studied, exhibit what may be 



^ I cannot agree with the position of Calkins and Gregory ('13) which appears 

 to be essentially that in order to 'prove' the 'immortality' of the Protozoa they 

 must be bred through eternity. The generally accepted work of Woodruff with 

 a race of Paramaecium aurelia has established beyond the question of a doubt, 

 I believe, that in this form at least an indefinite and unlimited multiplication 

 without conjugation or artificial stimulation may be had, provided suitable cul- 

 ture conditions are supplied. The experiments in these studies show that the 

 same holds true for at least one of the hypotrichous Infusoria and also that the 

 so-called life cycle may be greatly and variously modified, depending upon the 

 conditions in which the animals are bred. 



