INTRODUCTION. 
IX 
enemies, should have been acquired by all, instead of being confined to a few only, as is the 
case. The most striking case of all is perhaps that of the females of the Swallow-tailed 
Butterfly, Papilio memnon, assuming the form and colouring of P. coon, another somewhat 
similar Butterfly ; the eminent naturalist who first drew attention to the fact, ascribed it to 
the immunity that the gioup to which the latter belongs, enjoys from the attacks of birds, 
and that in this way the mimicking females escape from persecution. We have often watched 
the Indian representatives of these species, which exhibit the same peculiarity, but have not 
noticed that any of them were specially liable to the attacks of either birds or dragonflies, so 
that we cannot from our own experience substantiate this point ; granting, however, that it 
is so, we have a most astounding fact — out of a single batch of eggs, in one portion the 
transition to another species (supposed to require countless minute gradations and links) com- 
plete in a single birth, in the remaining portion the change not even commenced, and no 
intermediate stage. If this extraordinary phenomenon is to be attributed to an external 
cause, it would be worth while considering whether this results from a fixed law of instinct 
01 fiom volition— if the latter, by whose volition it is performed, by that of the parent or by 
that ot the offspring also why the whole batch do not adopt the remedy, and, lastly, how 
the question is settled as to which shall put on the deceptive livery and which remain victims. 
The facts are marvellous ; but the explanations are more puzzling still. 
As regards the minute variations in colouring and size which separate closely allied species, 
and especially slight differences peculiar to local distribution, we cannot consider that they 
oftei any obstacle to a belief in the common origin of the species so allied, though it has not 
as yet been sufficiently proven for us to insist upon it : neither, on the other hand, is it part 
ot our zoological faith to maintain that all gaps in form were once filled up by a countless 
series of links— though to admit that they may have been so connected opens out a wide field 
or inquiry, of the deepest interest, and gives a renewed zest to the collection of facts hearing 
on the subject. Especially valuable are such researches as those of Mr. A. R. Wallace, 
which reveal to us so much of the really natural history of the animal kingdom, and which 
enable us to compare the results arrived at through the observations of domesticated animals, 
and of those whose conditions of life have been modified by the encroachments of civilization' 
with those of which the conditions have been uninfluenced in any way by man. Though it 
is quite true that man does not produce variability, it is nevertheless certain that by changing 
the conditions of life he calls into play that which was previously dormant ; and the obser- 
i ations of animals in civilized countries only can never carry the same amount of conviction 
in support of an hypothesis as those carried on in a wild country and on animals in a primitive 
state. To the assertion that there is no obvious reason why the principles that have acted so 
efficiently under domestication should not have acted under nature, we reply that there is a 
reason to be deduced from the very obvious fact that the wild Dog, the wild Fowl, the wild 
Duck, the wild Pigeon, the wild Cat, the wild Horse, remain to this day single species, 
while of the domestic varieties claiming descent from them the name is legion a fact 
almost conclusive in showing that these principles do not act where the conditions of life 
are invariable, but that where these have changed, either through man’s influence, climate, 
or any other cause, the capability of variation has from time to time most probably been 
b 
