EFFECTS OF REORGANIZATION ON VITALITY oot 



directly induces not only an immediate acceleration of reproduction 

 but also an acceleration which persists at least as long as the life 

 of the parental cultures. These results are in opposition to all 

 results which indicate that conjugation is devoid of a profound 

 physiological stimulation of the metabolic activities of the cell 

 expressed in reproduction" (loc. cit., p. 189). Thus in Spathidium 

 spathula not only are the division-rates of ex-conjugants higher 

 than those of the parental strains but the ex-conjugants actually 

 outlive the parent ])rot()])Iasm, hence the authors further conclude: 

 "Conjugation typically has a high survival value in the life of the 

 organism" (p. 196). 



It is significant that Woodruff and Spencer studiously avoid use 

 of the term "rejuvenescence" in their work. They speak of an 

 increased division-rate of ex-conjugants and of the "survival value" 

 of conjugation but not of renewal of vitality. As these are the two 

 essential factors which characterize the phenomena of rejuvenes- 

 cence we are justified in including Woodruff among the proponents 

 of rejuvenescence. The two factors were discussed in an earlier 

 analysis of rejuvenescence (Calkins, 1920) in which it was pointed 

 out that the division-rate expresses the "intensity" of vitality and 

 the length of life in division days the "endurance;" the latter is 

 evidently the same as Woodruft' and Spencer's "survival value." 



The experimental work on Spathidium spathnia was a confirma- 

 tion of the work on Uroleptns mobilis which was begun in 1917, 

 and is still under way. A single ex-conjugant was the progenitor 

 of all the material that has formed the subject of the investigation. 

 The method employed throughout was the usual isolation culture 

 method (see p. 4(39). In the following account of the experiments 

 the term "series" always means an ex-conjugant with the progeny 

 formed from it by division; the progeny being represented by five 

 pure lines which are continued by isolation cultures until vitality 

 is exhausted and death ensues. Conjugation tests at regular 

 intervals provide material for filial series.^ Up to January 1, 1925, 

 125 different series had been studied; 116 of them had followed the 

 usual history and had died out and 9 series were under culture. 

 The last of these 9 series represents the F 29 generation of successive 

 conjugations since the original ex-conjugant was isolated. Abundant 

 statistical data have accumulated during these seven years and 

 these furnish valuable evidence in favor of the theory of rejuvenes- 

 cence. The bearing of these data on the following topics may be 

 briefly summarized : (1) Renewal of vitality as a result of conjuga- 

 tion; (2) intensity of vitality and extent of renewal; (3) eft'ect of 

 parents' age and vitality upon vitality of offspring; (4) evidences 



' In the earlier publications on Uroleptus these series were designated by letters 

 as Series A, Series C, etc., but with the exhaustion of the alphabet the letters have 

 been replaced by serial numbers. 



