60i ) 



THE AMERICAN NATURALIST [Vol. XLIX 



age length of the zygospores produced by lateral con- 

 jugation exceeds the mean of the scalariform conjugants 

 by 1.94 microns, while the probable error for the first 

 constant is + .1776 and for the second constant +.1345. 

 The difference is therefore a significant one so far as the 

 present material is concerned. 



It is in the comparison of the standard deviations (<r) 

 and the coefficients of variation (C. V.) that the results of 

 most interest appear, however. The former constant in 

 lateral conjugation has a value of 1.6986 in excess of the 

 same constant in scalariform conjugation, or relatively 

 29 per cent. This is more than thirteen times the prob- 

 able error. In the coefficient of variation, an abstract 

 number permitting comparison with similar constants in 

 other organisms, the results indicate that the variability 

 in lateral conjugation exceeds that occurring in scalari- 

 form conjugation by 2.4271 or relatively 26 per cent., a 

 result corroborated by the distribution of the diameters. 

 The probable errors are sufficiently small in comparison 

 with the differences noted, that they may be considered 

 negligible. 



Skewness is negative in the curve for lateral conjuga- 

 tion, the mean being on the left side of the mode, but its 

 value is less than the probable error. In the curve for 

 scalariform conjugation skewness is positive with a value 



