106 THE SHORTER SCIENTIFIC PAPERS 



distribution of diameters. The more extended as well as 

 the more irregular distribution of lengths of the lateral 

 zygospores when compared with the scalariform zygo- 

 spores is at once suggestive that the group thus close bred, 

 is the more variable one. It is also of some interest to 

 note that the empirical range of variation for the laterally 

 formed zygospores, — with length from 49 m. to 83 m., — 

 is considerably greater than in the scalariform zygospores 

 with lengths from 47 m. to 79 m. While this is not a 

 measure of statistical variability, it undoubtedly has a 

 genetic value. 



The general constants for the variability in the length 

 of the zygospore of the two groups are shown below. It 

 may be noted that the mean (M.) or average length of 

 the zygospores produced by lateral conjugation 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 (o") 

 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 

 slightly more than three times the probable error. There- 



