124 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE 



In connection with the difference in the variability of 

 close bred and cross bred zygospores it seems quite evident 

 that the result is brought about by some factor other than 

 the environmental stimuli are assumed to produce fluctua- 

 tion inasmuch as the material was homogenous in every 

 respect with the exception of the manner of reproduc- 

 tion. The question is a difficult one, however, not to be set- 

 tled by a single investigation giving positive results, and 

 because of its importance should receive attention. 



In reference to those who hold to the belief that cross 

 breeding, conjugation, and amphimixis — the three terms 

 differ merely in degree — increase variability, it may be 

 well to inquire concerning some of the evidence instru- 

 mental in formulating the opinion. Without any desire 

 to be critical and at some risk of exceeding the con- 

 troversial bounds which a paper of this nature allows, a few 

 of the more important investigations touching upon the sub- 

 ject will be considered. 



Castle, Carpenter, Clark, Mast, and Barrows (1906) in 

 a series of observations as to the effect of cross breeding 

 and close breeding on the variability and fertility of the 

 small fruit fly, Drosophila ampelophila Loew. stated that 

 "inbreeding did not affect the variability in the numb9r of 

 teeth on the sex-comb of the male, nor the variability in 

 size," basing the opinion on the Coefficient of Variation in 

 the number of spines and the Standard Deviation in the 

 length of the tibia. In the former case the data certainly 

 do not permit a clear conclusion one way or the other, but 

 the value of the character which represents the sum of the 

 teeth of the sex combs of the right and left proximal tarsal 

 segment, where there is undoubtedly correlation, may be 

 open to objection under any consideration. If however, 

 from the data presented in the study the value of the Coeffi- 

 cient of Variation is computed, which strange to say was 

 not done in the original paper, and thus allowance made for 

 the larger mean length of tibia in the cross bred forms, the 



