VITALITY 477 



from those used for the series that showed decKne and death, he 

 conchides that somehow, the conditions were more suitable, and 

 that when suitable the ciliate has the ability or potential for an 

 indefinitely continued existence without the necessity of conjugation 

 (fertilization) or of an equivalent process. 



Chatton (1921) shares this scepticism: "One may even conclude" 

 he says, "that the more the facts accumulate, especially those of 

 an experimental nature, the more nebulous does this conception 

 of a life cycle (in ciliates) become" (loc. cit. p. 128). The "facts" 

 thus mentioned include the exceptional results with experimental 

 culture methods by Woodrutf as above, by Baitsell, Dawson, 

 Enriques, Mast and others, these being the most prominent, in 

 connection with the Infusoria. As stated above Baitsell (1914) 

 using Oxytricha falla.v and Pleurofricha lanceolata in isolation cul- 

 tures, obtained results exactly similar to those obtained with 

 Uroleptvs. For each series the cycle began with high initial vitality 

 which slowly decreased with age until death resulted (F'ig. 199). 

 Other series, however, were cidtivated in test-tubes and in some 

 cases these continued to live longer than did the individuals of the 

 isolation series. At the time of writing his paper one of these cul- 

 tures was still alive (Pleurotricha lanceolata) six months after the 

 isolation cultures had died. Other mass cultures, although out- 

 living the isolation cultures died (Oxytricha fallax). From these 

 results which are not altogether convincing nor consistent, Baitsell 

 concluded that these animals can be bred indefinitely without 

 conjugation or artificial stimulation. The death of all individuals 

 in other mass cultures was attributed to the "cumulative effects 

 of an environment not entirely adapted to the organism." Here 

 again we meet with the idea that if a race dies as it does in the great 

 majority of cases, it is evidence that external conditions are unsuit- 

 able. The one race of Baitsell's that continued to live in test-tube 

 mass cultures is obviously an exceptional case and requires explana- 

 tion. In such mass cultures many things may happen which do not 

 happen in isolation cultures and are easily overlooked. The 

 endurance factor of vitality may preponderate over the intensity 

 factor (in some cases of Uroleptus mohilis single individuals lived 

 without division for ninety days). Conjugations may occur and 

 be overlooked where hundreds of individuals are examined in a 

 test-tube, even though such examinations may be made daily and 

 thoroughly. One single ex-conjugant w^ould be sufficient to upset 

 the conclusions drawn from this experiment. 



In a similar manner Dawson (1919) found that an amicronucleate 

 race of Oxytricha hymenostoma presents a typical cyclical curve 

 of vitality and death follows a gradually decreasing vitality, if the 

 organisms are cultivated in isolation cultures. If maintained in 

 mass cultures they were found to li^'e for a considerable period 



