66 
The Birds of India. 
cock and tlie lien that they have been mistaken for difFetent species. Tlius 
we have in India, living side by side, fonr widely distributed species of dove, 
all having similar habits, and in three of these species the sexes are alike in 
appearance, while, in the fourth, they display considerable differences. 
Wliy this should be so, no neo-Darwinian has attempted to explain. l'"acts 
such as these seem to be left severely alone by Weisniann and his followers. 
So-CAi^LED Mimicry. 
The avifauna of India furnishes zoologists with what some of them, 
at any rate, are pleased to term a most striking case of mimicry. Among 
birds and beasts certain species have their doubles. Now, when two species, 
which are not near blood relations, are alike in appearance, and this like- 
ness appears to be advantageous to one of the two species, this latter is said, 
in biological parlance, to mimic tlie other. vSuch mimicry is, of course, 
unconscious. It is commonly supposeil to have ))een brought about b\' 
natural selection. Now, there is in India, a cuckoo — the Drougo-cuckoo 
(Surniciiliis liigiibris) — which resembles in appearance the common King- 
crow {Dicruius ater.) Further the cuckoo is parasitic on the King-crow. 
Now, this last is, as we have seen, a very pugnacious bird, especially at the 
nesting season. It guards its nursery with great ferocity. I have watclied 
a pair of these little birds attack and drive away a monkev' which tried to 
climb into the tree in which their nest was placed. Indeed, so able a fighter 
is the King-crow that some other birds — notably orioles and doves, which 
also are ver\' pugnacious, frequentlj' build their nests in the same trees as 
the King-crow, in order to share tlie benefit of his prowess. It would be 
almost impossible to deposit eggs in the nest of a bird so pugnacious as the 
King-crow without resorting to guile. But the Drongo-cuckoo is as like 
the King-crow in appearance as one pea is like another. I5oth are small 
glossy black birds with a longish forked tail. Now, zoologists, seeing how 
the cuckoo profits by tliis resemblance, declare that it mimics the King- 
crow, and that this resemblance has been brought about by natural selection. 
The theory sounds very i)lausible, but close inspection reveals its weak 
points. The King-crow is no fool, so that in order that the cuckoo nia}' 
delude him into the belief that it is a fellow king-crow the likeness 
must be fairly close, lint the average cuckoo is not in the least like the 
King-crow in appearance, so that no small variation in the direction of King- 
crow appearance would be of any use to it. Hence this remarkable resem- 
blance must in the first place have arisen fortuitously, or rather, causes 
similar to those which effected the nigritude of the King-ciow must liave 
made the ancestral l)rongc)-cuckoo black. But we are as j et more or less in 
tlie liark as to what has caused the King-crow to be black, so that we are not 
ill a })osition to say how it was that this species of cuckoo came to resemble 
the drongo in appearance. 
In attempting to account for any characteristic of an organism by 
