MR. A. MUREAY ON MIMETIC ANALOGY. 
115 
it congenial or habitable ; and although it might live long enough 
in it to found a dynasty of mimickers, it would soon die off from 
unsuitable conditions, while its hybrid offspring bred from the 
tropical Danaids might, from the black blood so imparted to them, 
find it sufficiently well suited for them. 
There is yet another phenomenon connected with mimicry, 
which possibly may also be connected with hybridization, viz. 
the occurrence of what Mr. Wallace has called dimorphism in 
insects among the mimicking or mimicked species. We must 
not, however, confound this dimorphism with Darwin's dimor- 
phism in plants. The two are totally different things, and, as it 
seems to me, have no relation or analogy to each other. In 
plants the dimorphism is always confined to the reproductive 
organs, in insects it has apparently nothing to do with them. 
Moreover, it seems to me that all the instances of so-called 
dimorphism in insects that have yet been recorded are nothing 
but examples of variation, perhaps complicated by hybridization. 
M. Eeinhard, of Bautzen, has shown that this is the case with 
regard to Mr. Walsh's conclusions respecting the dimorphism 
of certain gall-flies ; for he had found that the galls of various 
species appear to be so transitional between other forms, that 
they can only be known with certainty when the perfect insect 
appears. It appears to me to be also the case in all those 
instances where the dimorphism is confined to particular districts, 
as in the I^apilio Turnus of North America, where all the females 
are yellow in the ]^ew England States and in JN'ew York, while 
in Illinois, and further south, they are all black, and in the 
intermediate region both black and yellow females occur in 
varying proportions. And the case is not open to any doubt, 
because in the intermediate district both yellow and black in- 
sects have been bred from the same batch of eggs. Now, if the 
case had been that hoth males and females equally varied, and 
that in the south all were black and in the north all yellow, with 
intermediate gradations in the districts between, we scarcely 
suppose that any one would have thought of calling it a case of 
dimorphism. If they did, then all climatal variations (and their 
name is legion) would come under the same category. It is only 
dimorphism, because the change is limited to the female. But is 
this a good ground ? Physiologists are unanimous in holding 
that neither the male nor the female is the species, but both ; and 
if that be the case, in what does a variation in the female and not 
