PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE 125 



inbred forms exhibit a variability relatively 68 per cent. 

 greater than the cross bred forms. 



Jennings (1911) in summarizing breeding experiments 

 with Paramecium concluded that "The progeny of conju- 

 gants are more variable in size and in certain other respects 

 than the progeny of the equivalent non-con jugants," and 

 farther, "Thus conjugation increases variation." Continu- 

 ing the investigations, he subsequently stated (1913) that 

 conjugation increased the variation in the rate of reproduc- 

 tion. While the careful methods used by Jennings have 

 brought to light many interesting and valuable facts, it is 

 evident from a critical consideration of the data that they 

 by no means allow such conclusions. 



So far as size is concerned in a Pure Race, non-con ju- 

 gants and their progeny were more variable than con ju- 

 gants and their progeny as noted in table No. 28. In a Wild 

 Race the progeny of the con jugants were slightly more 

 variable than the progeny of the non-con jugants as illus- 

 trated in table No. 32, although in two of the nine genera- 

 tions tabulated the variability was greater in the case of 

 the non-con jugants. So far as the rate of fission is con- 

 cerned the evidence is unmistakable that the con jugants 

 were more variable. There is, however, a comparatively 

 simple explanation for this when the statement is noted 

 that the number of abnormal individuals as well as the mor- 

 tality was greatest among the progeny of the con jugants. 

 With a considerable number of forms thus having a lower 

 rate of fission, one could expect nothing except a greater 

 variability in the rate of fission. 



Considering the data obtained in the breeding of plant 

 forms where the assumption has long been prevalent that 

 hybridization increases variability, it is found that the 

 variability of the F. generation as compared with the F, 

 generation or a single parental generation may be increased 

 but that the actual variability as a whole is not increased 

 when the united parental types are taken into account. This 

 may be illustrated by utilizing data from an interesting 



