110 REPORT OF THE CONFERENCE ON GENETICS. 
As to the dimensions also we cannot find any greater variability in 
hybrids. But they have always shown a much smaller coefficient of 
excess than the pure lines. The standard deviation or coefficient of 
variability being almost identical, this means clearly that the greatest 
deviations from the mean are relatively more numerous in our pure lines 
than in their hybrids. These fluctuate more in accordance with the 
“normal frequency curve ’’ than their pure parent lines. These also have 
a greater skewness in their curves than the hybrids. 
Resuming these experiments, it may be said that the fluctuations as 
to weight and dimensions in the pure lines were not less than in their 
hybrids ; here was no increased amplitude of variability, offering any better 
material for selection. The contrary was rather the case as expressed 
by the higher “ excesses”’ in the pure lines. These results may also be 
regarded as an answer to the criticism which maintained that my pure 
lines should present diminished fluctuations ! 
It is now my task to observe the progeny of the hybrids through a 
series of generations in the same manner as [ have observed several pure 
lines. To judge from some few breeding experiments in the greenhouse, 
there will be found Mendelian segregations as to dimensions and weights. 
This matter will be observed more closely, and the isolation of the new 
type-combinations shall be carried out. In this manner what may be 
called “ unit-characters ’’ as to length, breadth, indices, weight and so on 
will be elucidated. I hope to find some quantitatively estimated traits 
that not only blend in the first generation of hybrids, but do not 
segregate at all. The exact quantitative study of such hyprids is still to 
be performed. | 
At all events it seems to me now that we have no reason to suppose 
that an augmented fluctuation will be found in the new types which here 
may be formed by segregations and new combinations. Further research 
will, I have every conviction, give greater clearness as to the fundamental 
distinction of true type differences and fluctuations. The way out of 
the confusion in the struggling theories of heredity and evolution is 
by exact biclogical analysis; mathematics may here be a good and 
indispensable servant, but not the commander! “ Treatment ’’—mathe- 
matical, philosophical, and fantastical—may be disputable ; what we want 
—in much higher degree than commonly admitted—are well analysed 
pure and clear elementary premises. 
Continuity of evolution is the most beautiful idea of modern biological 
philosophy ; we all may love this idea and have some hope of its being 
true, but in reality not one indisputable fact as yet proves it. And are 
not the results of modern chemistry speaking loudly of discontinuity as 
a fundamental fact in nature ? 
APPENDIX. 
After writing this paper, I received, by the kindness of Mr. Darbishire, 
his very interesting pamphlet “ On the Differences between Physiological and 
Statistical Laws of Heredity’ (from Memoirs and Proceedings of the Manchester 
Lit. and Phil. Soe., vol. 1. Part III., 1906). The author attacks his problem on 
another ground than that upon which my criticisms as to statistical treatment of 
heredity are based; so far we supplement each other. It will be evident to 
