LEE BARKER WALTON 113 



permit a clear conclusian one way or the other. In the 

 second case, however, if the value of the coefficient of 

 variation is computed for the length of the tibia — which, 

 strange to say, was not done in the original investigation 

 — and thus allowance made for the greater length of tibia 

 in the cross-bred forms the average variability of the 

 three inbred groups is 68 per cent greater than that of the 

 cross-bred group. Consequently, the results decidedly 

 support the facts in the present paper. 



The remaining papers are those of Jennings ('11 and 

 *13) in a study of 'Paramechnn. In the first paper the 

 breeding experiments are summarized as follows: 



The progeny of conjugants are more variable, in size and in certain 

 other respects, than the progeny of the equivalent non-conjugants. 

 Thus conjugation increases variation. 



It seems difficult to account for this conclusion if one 

 subjects the data to a critical review. So far as a "pure 

 race" is concerned the non-conjugants and their progeny 

 were decidedly more variable than the conjugants and 

 their progeny, although the small number utilized March 

 31 for the statistical work (42 and 34) is not sufficient 

 to justify a conclusion in either direction. Even in a 

 "wild culture" the evidence is too conflicting to justify a 

 definite expression of opinion. Of the seven comparisons 

 here made among the progeny, five showed an excess 

 variability for the conjugants, but in only one case did 

 the difference exceed three times the probable error, while 

 two cases showed an excess variability for the non-con- 

 jugants, the difference in one case exceeding twice the 

 probable error. Data from numbers so small (22-95) 

 can scarcely be considered reliable. The comparison of 

 the variability of "all pairs" and "all unpairs" on June 22 

 and June 23 denotes an excess variability for those com- 

 pleting conjugation at the beginning of the experiment. 



In the second paper Jennings concluded (p. 363) that 

 conjugation increased the variation in the rate of repro- 

 duction. The variation was increased, but the explana- 

 tion of such increase seems comparatively simple when 

 it is noted that among the conjugants there were many 

 with a low rate of fission with death occurring. As com- 



