496 
Charles Edward Walker, On Variations in Ckromosomes. 
might well be in a period of species formation" 1 ). It is difficult to under- 
stand how any difference in the behaviour of a chromo- 
soine eould affect a cliaracter conveyed by it, but that an alteration of 
shape or size might do so seems clear enough. Constant and continual 
variations among chromosomes would also account for the constant and 
continual variations that appear in animals and plants, without neces- 
sitating recourse to the mutation theory and the assumption that varia- 
tions occur only in epidemics at intervals, species only arising during 
these epidemics. 
x ) '‘On the Dimegalous Spenns and Chromosomal Variations of Euchistus, etc.” 
Archiv f. Zellforschung. Bd. V. H. 1. 1910. 
