The Gall Wasp Genus Cynips 
PART I. THE ORIGIN OF SPECIES 
Among the diverse aspects of the so-called species problem, 
there is none that has received more unsatisfactory treatment 
than the study of species. The data of morphology and pa- 
leontology have given us information on the origin of orders 
and classes and phyla, and the geneticists and cytologists have 
contributed a brilliant interpretation of the mechanism which 
accounts for the similarities and, ipso facto, for the differences 
between individuals of successive generations; but compara- 
tive studies of species, first-hand contacts in the field with 
thousands of individuals of hundreds of related species, the 
careful examination of these individuals with modern labora- 
tory facilities, and the correlation of such studies with the 
findings of genetics, cytology, and the other sciences — in 
short, the thoro taxonomic study of species has only occa- 
sionally been accomplished. 
Our present account of the gall wasp genus Cynips is offered 
as an intensive study of 93 species of a phylogenetically natu- 
ral group. It has been possible to translate so much of the 
story because the genus is a highly specialized unit of such 
recent (Oligocene or Miocene) origin that there are no serious 
gaps in the record as we find it today. The galls produced by 
these wasps are direct measures of one of the physiologic 
capacities of the insects, and thus afford an opportunity for 
the study of physiologic as well as morphologic variation 
within the group. The precise restriction of each species to 
particular hosts gives us an opportunity to analyze the rela- 
tion of isolation to the origin of species, and the relatively 
poor means of locomotion of most of the gall wasps accounts 
for considerable geographic variation with its further empha- 
sis on isolation. The existence of 42 sub apterous forms in 
the genus has afforded an unexpected opportunity to show the 
relation of mutation to the origin of species. All of these 
items contribute to the utility of these insects for the study 
of the general problem of evolution. Whether species in the 
genus Cynips present a fair picture of species in general can 
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