448 
[March 
O. S., occurs exclusively in the 9 sex and exclusively on q. tinctoria. 
and emerges from the last of September to the middle of November, 
and many of them not till the following spring, from galls that com¬ 
menced their growth in the preceding May, which are undistinguish- 
able from those which produce C. q. spongifica^ the same kinds of gall 
from the same lot of trees, gathered at the same time, producing spon- 
gifica S 9 June and aciciilata 9 in October and November, and 
nothing whatever but a solitary parasite in the intervening period. 
Suppose, for argument’s sake, that aciculata and spoyigifica are dis¬ 
tinct species. Then we are met immediately by the following difficul¬ 
ties :—l.si'. Is it likely that two distinct species of Cijnips should pro¬ 
duce, on the same species of oak, galls which are undistinguishable ? I 
know of no such case in the whole Class Insecta. 2nd. Is it likely that 
when spongijica., as above shown, is so local that it is only found in 
one station out of fifty near Rock Island, acicidata should select that 
particular station instead of some other one of the remaining 49 ? 
If aciculata is a distinct species, then we are compelled to believe with 
Hartig in the existence of agamous species, i. e. of species that propa¬ 
gate from year to year ad infinitum without sexual intercourse with a 
distinct individual. I cannot believe that any species in the whole 
Animal Kingdom is uniformly agamous, for the simple reason that we 
should then have almost as many races, and finally species, as individ¬ 
uals. Monstrosities and remarkable variations, which with bisexual 
species are mostly eliminated by intercrossing with normal individuals, 
would then by the laws of inheritance be always intensified and exag¬ 
gerated from generation to generation, and what was originally one 
homogeneous species would split up into an almost infinite number of 
distinct and sharply defined types.* 
That it may not be supposed that I approached this subject bias¬ 
sed in favor of the conclusions above announced, it is proper to state 
that my original guess was, that there were two broods of this Gynipis 
every year, the first a spring brood h 9 spongifica^ the 
second an autumnal brood, 9 only, of the type aciculata., generated in 
the ordinary course by the first brood, and in its turn generating by 
'!• Mr. Darwin has avowed a similar belief in the case of hermaphrodite spe¬ 
cies, but for a different reason, viz., that close interbreeding tends to produce 
sterility. {Origin of Species, p. 235, Amer. edition.) 
