60 CONTROLLED NATURAL SELECTION 



usually form specific characters and acquired 

 characters do not, it follows that the char- 

 acters to do with protection from enemies are 

 likely to be very important ones. 



Much criticism has been levelled against natural selec- 

 tion from a mathematical point of view, and especially as 

 regards the swamping effects of chance. If chance kills 

 off 950 of a 1000 individuals, then natural selection has 

 50 instead of 1000 to work with. However, the effect 

 must be the same, except that longer time will be re- 

 quired for the origin of favourable variations. When, 

 however, after perhaps many generations the favourable 

 variation does arise and escape the hands of chance, then 

 it will be one amongst 50 instead of one in 1000, and 

 therefore less likely to be swamped. 



False examples of chance are often cited. The stepping 

 of a horse on an ant's nest is a typical one. The action 

 of the horse may be the result of chance. But what can 

 be said about the position of the nest ? The mother ant 

 in the past chose this particular spot for her nest. Other 

 mothers chose in some cases no doubt places where horses 

 are not likely to walk. Will not such mothers therefore 

 be thus selected to carry on the race? 



In conclusion it may be said that, although 

 the subject has been approached from several 

 standpoints, reasoning has led in each case to 

 the same two conclusions : 



1. Specific environments are more impor- 

 tant than common environments as selecting 

 agents. 



2. Species' enemies are very important 



