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Indiana University Studies 
Osborn, it may be added, is in accord with this opinion of the 
minor importance of mutation. Bateson (1922) spoke for 
many of the geneticists when he expressed the same un- 
certainty of the application of the laboratory data to species 
in nature, and recently Anderson (1928) concludes a field and 
genetic study of two species of iris with the statement that 
there is little in his evidence to support the mutation theory 
of the origin of species. 
Now, the problem of species obviously goes back to the 
recognition of the factors which may affect the potentialities 
of genes. I have nothing to contribute on this aspect of the 
subject. It is to an increased knowledge of the physico- 
chemical nature of protoplasm and of the gene, and to such 
experimental work as that of Muller and others on mutations 
affected by the introduction of measurable amounts of energy, 
that we must look for the explanation of the first step in the 
process of evolution. But granting that mutations do on 
occasion occur, we may present a body of new data to show 
that these laboratory mutants are precisely the materials 
which have differentiated many of the species of our genus 
Cynips. 
This evidence becomes available because there are, in the 
family Cynipidae, more than 70 species of gall makers which 
have rudimentary or reduced wings strikingly different from 
the long wings normal among the other seven or eight hun- 
dred described species of the family. The differences between 
these two types of insects are illustrated on several of the 
plates accompanying this paper. Material on all of these 70 
species will be brought together in a later study, but it may 
be said that all of the data support and extend that part which 
is here presented on the genus Cynips. 
The typical wasp of the family Cynipidae has wings which 
are somewhat longer than its body. The wings even approach 
twice the body length (a wing-body ratio approaching 2.00) 
in certain genera of Cynipidae. The normal wings vary be- 
tween the different genera and subgenera, but are remark- 
ably constant among the individuals of each taxonomic group. 
Thus the normal ratio is always about 1.35 in the subgenus 
Atrusca, 1.50 in the subgenera Beshicus and Cynips , and 1.60 
in the subgenus Antron. On the other hand, many Cynipidae 
have wings less than one-fifth the body length (ratios under 
