A MELODIOUS DRONGO 131 



uncommon in India. As we have seen, its distribution 

 is wide, so that it seems able to adapt itself to various 

 kinds of climate. Nevertheless, it is common nowhere 

 in India. What is the cause that keeps down its 

 numbers ? NaturaHsts are wont to talk airily about 

 natural selection causing a species to be numerous or 

 the reverse, but imless they can show precisely how 

 natural selection acts they explain nothing. Those 

 who write books on natural history convey the im- 

 pression that it is the birds and beasts of prey that keep 

 down the numbers of the smaller fry. As a matter of 

 fact, predaceous creatures seem to exercise but little 

 influence on the numbers of their quarry. There are 

 hidden causes at work of which we know almost noth- 

 ing. Damp and small parasites are probably far more 

 powerful checks on multiplication than predaceous 

 creatures. It would seem that there is something in 

 the constitution of the white-bellied drongo which 

 enables it to outnumber the king crows proper in 

 Ceylon, but which prevents it from becoming abundant 

 in the peninsula of India. What this something is we 

 have yet to discover. We really know very little of the 

 nature of that mysterious force with which naturalists 

 love to conjure, and which Darsvin named Natural 

 Selection. We write it with a capital N and a capital S, 

 and then imagine that w^e have explained everything. 



" Twinkle, twinkle, little star, 

 Now we all know what you are." 



