178 BLASTOaENIC VARIATIONS. 



some of the dark green variety appeared in broods of 

 the typical yellow variety, and in one instance some of 

 the yellow variety in broods of the dark green. These 

 sudden transformations could not have been due to ex- 

 ternal circumstances, as the two forms appeared in the 

 same aquaria, under precisely the same conditions. 

 Weismann attributes them to reversion. 



Evidence telling in the opposite direction to Weis- 

 mann's has recently been obtained by Warren,* and as 

 it is based on exact statistical measurements, one is in- 

 clined at first sight to attach greater weight to it. The 

 observations consisted in measurements of the total 

 length of body to base of spine, and of the length of the 

 protopodite of the second antenna of the right side, in 

 23 female Daphnia magna, and their 96 partheno- 

 genetically produced offspring. As these animals con- 

 tinue to grow throughout life, the second dimension 

 was expressed in terms of the first, before calculating 

 its variability. Its error of mean square, or standard 

 deviation, was found to be 2.22 in the mothers, and 

 2.95 in the offspring. That is to say, the offspring were 

 distinctly more variable than the mothers, and even the 

 offspring of a single mother were found to be on an 

 average more variable than all the mothers put to- 

 gether. As the mothers had in a way been selected, 

 only those which produced offspring being chosen, the 

 daughters would be expected to be somewhat more vari- 

 able, but in any case the variability was considerable. 

 Again, it was found that the coefficient of correlation 

 between mother and offspring was .446, whilst the co- 

 efficient of regression of offspring on mothers was .619. 

 *Proc. Roy. Soc., Ixv. p. 154, 1899. 



