EFFECTS OF REORGANIZATION ON VITALITY 



565 



in the Table, p. 560 by an asterisk. The vitahty of the first sixty 

 days of a cyst series is compared with that of the parent series for 

 the sixty days following encystment and the results are practically 

 the same as with ex-conjiigants. In some cases the cysts are kept 

 dried for a period of weeks or months but this has no effect upon 

 the vitality of the organism when it emerges. In all cases the 

 evidence of rejuvenescence is the same as for ex-con jugants from 

 young series. 



The general results of these experiments with Uroleptus mobilis 

 leave little groand for reasonable doubt of the rejuvenating effect 

 of conjugation. The view of Woodruff and Spencer (1924) that 

 loss of vitality and death here are due to conditions of the milieu 

 seems rather far-fetched when we consider that series after series 

 with the similar sequence of renewed, waning, and exhausted 



Fig. 233. — Kanjamceba falcata. (After Kofoid and Swezy.) 



vitality pass by in ai)parently endless succession, and all in the 

 same milieu so far as it is possible to make it the same, from the 

 beginning of the experiments eight years ago to the present. • It is 

 quite a different question whether or not conditions of the medium 

 can be so altered as to bring about the same results as conjugation. 

 The explanation must be looked for in the protoplasmic happenings 

 at the period of conjugation or of endomixis (see Chapter XI). 

 In both cases these result in a rearrangement of the chromatin and 

 cytoplasm which according to Erdmann (1921) gives rise to new 

 sets of autocatalyzers and new cytoplasmic matrices for their 

 activation. 



Nothing is known about the effect of encystment on vitality in 

 the Sarcodina or Mastigophora. There is no a yriori reason to 

 doubt that as in ciliates reorganization is accomplished during 



