Checks on Increase 



moonlight these creatures were really not at all 

 conspicuous, indeed that they were obliteratively 

 coloured. In other words, a totally wrong ex- 

 planation of their colouring would be given and 

 accepted. It is our belief that many of the 

 explanations put forward and accepted of the 

 colouration of existing species are wide of the mark. 



As all bee-keepers are aware, the disease 

 known as foul-brood works more havoc among 

 their bees than all the insectivorous creatures 

 put together. 



Similarly throat disease among wood-pigeons 

 does more towards keeping their numbers down 

 than all the efforts of predacious birds. 



A check on multiplication not mentioned by 

 Darwin is that which is sometimes imposed by 

 the individuals of the species on one another. 

 Thus, in some animals, as, for example, the 

 hyaena, the male occasionally devours his own 

 young ones. 



A check of a similar nature results from the 

 habit which the Indian House Crow (Corvus 

 splendens) has of interrupting the pairing opera- 

 tions of its neighbours. 



We are now in a position to sum up briefly 

 the more important requisites for success in the 

 struggle for existence. 



These are not so much specialised structure as 

 courage, a good constitution, mental capacity and 

 prolificacy. 



z 353 



