Kinsey: Gall Wasp Genus Cynips 
19 
species. In one species which constitutes an exception to this 
generalization, mutations are involved, and these will be 
treated in a later section of this paper. 
Finally, the limits of variation of any character prove to 
be strikingly uniform thruout the great populations which we 
propose to call species. Whenever we have taken a reasonably 
large sample from any point over the usually considerable 
range of a species, the biometric data have not proved funda- 
mentally different from data for any other fair sample from 
any other point in the range. The case of Cynips erinacei 
will serve to illustrate our experience. Erinacei is not only 
the most variable Cynips but one of the most variable cynipids 
I have examined. Reference to the descriptions in the sys- 
tematic portion of this study will show that every one of the 
few characters which distinguish these insects from the most 
closely related species vary between limits approached by some 
one or another of the related species. The galls present more 
apparent variation, showing every gradation from smooth, 
naked, spherical, monothalamous structures (fig. 312) to 
densely spiny, ellipsoidal, polythalamous galls (fig. 315) which 
may have as many as eight larval cells. An initial experience 
with these extreme types of galls would lead one to believe 
they represented distinct species, and so they have always 
been classified heretofore. Increased material, however, has 
shown that every extreme and every one of the intermediate 
characters occurs thruout the range of erinacei. 
The range of this species extends about 1,300 miles east and 
west and 450 miles north and south. We have samples of 
erinacei from nearly a hundred localities fairly well dis- 
tributed over this tremendous area of possibly 500,000 square 
miles. In every large sample, erinacei is as variable as we 
have described it, and yet, after all, it is everywhere uniform 
— uniform in its constancy of variation. Even erinacei is, 
then, the sort of population which we would call a species. 
Erinoxei may present an extreme case, but it is not funda- 
mentally different from the thing which one finds everywhere 
in nature. It is moreover, the picture of species to which our 
knowledge of mutation and Mendelian hybridization would 
lead us, and our definition of species must become genetic if 
we take into account the similarities and the differences which 
we find within a species. The essential uniformity of most 
