578 BIOLOGY OF THE PROTOZOA 



We have here a clear case of Mendehan segregation and a par- 

 celing-oiit of the germinal make-up in a definite Mendelian ratio 

 which Pascher confirmed by direct observations in 5 different 

 cases and by mass cultures in 8 others. The parental characters 

 are sifted out and recombined to give organisms of a type different 

 from either parent. In a single operation, and evidently through 

 meiosis and fertilization, results of a similar nature to those obtained 

 by Jennings after prolonged selection, were obtained. 



Reference has already been made to the complete and elaborate 

 studies of Jennings (1913) on inheritance as it applies to reju- 

 venescence (supra p. 556) and we refer here only to his results in 

 regard to bi-parental inheritance (see also Jennings and Lashley 

 1913). No exception can be taken to the general conclusion that 

 "Conjugation results in bi-parental inheritance" (Jennings and 

 Lashley, p. 451). There is reason, however, for not accepting the 

 experimental evidence that is adduced in support and proof of 

 the conclusion. By experiment, observations, and use of bio- 

 metric methods, Jennings studied elaborate data of conjugants, 

 "split" conjugants, ex-conjugants and non-con jugants of Para- 

 mecium caudahnn and Paramecium aiireUa in respect to size, 

 division-rate, abnormalities and mortality. He found that mortality 

 is much higher in ex-conjugants than in non-con jugants or in split- 

 con jvigants; that the division-rate of ex-conjugants is uniformly 

 less than that of non-con jugants or split conjugants; that abnor- 

 malities are more frequent among ex-conjugants than among non- 

 conjugants or split-conjugants and that variations in respect to 

 these "heritable" characters are greatest among the ex-conjugants. 

 As to size there is no evidence at all : conjugationg individuals were 

 shown by biometric methods to be smaller than non-conjugants 

 of the same race (this is likewise true of most ciliates) but their 

 progeny were not smaller. The best evidence given for his con- 

 clusions lay in matters of mortality, division-rates, abnormalities 

 and variations of ex-conjugants. Dobell (1914) has pointed out 

 some of the logical difficulties in connection with these studies but 

 a more fundamental objection lies on the technical side. Quoting 

 from Dobell: "But as Jennings himself points out 'conjugation 

 increases the variation mainly toward the lower extremity of the 

 range'— that is, the effect of conjugation is to retard the rate of 

 fission. Is not this merely another aspect of the same condition 

 which is otherwise manifested as 'high mortality' and 'loss of vigor' 

 after conjugation? Jennings' Experiment (i seems to me the key to 

 the matter. 'This experiment as a whole shows the fact that after 

 conjugation the organisms are in a condition such that many may 

 die, while those that have not conjugated live; and the further fact 

 that the rate of reproduction is made slower by conjugation, remain- 

 ing in this condition for about two months' after which it has 



