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THE ZOOLOGIST. 



of good breeding, and makes the most " of every creature's 

 best." 



As an illustration of this law of Natural Selection, suppose, 

 says Darwin, that all the rabbits of a country were to perish, so 

 that the dogs and foxes required to subsist solely on hares. It 

 is evident that the longest limbed, most agile, and swiftest of 

 these predatory animals would be most successful in gaining 

 food in times of soarcity, and would rear most young, which 

 would tend to inherit such advantages ; while the less agile 

 would perish. And so with any animal which depended on its 

 speed, strength, weapons of offence and defence, either in regard 

 to obtaining food, or superiority in combat between males. 



[Another theory subsequently broached by Darwin and elabo- 

 rated at considerable length is that many of the variations are 

 due to the selective power of the animals themselves. Thus 

 female birds (which are generally clad in sober colours) choose 

 for mates the finest and most perfectly coloured males. The 

 strongest and most courageous males amongst deer and other 

 animals drive off their weaker brethren and select their partners. 

 Thus it is, he states, that special developments, such as horny 

 or warty appendages, the perfume of the Musk-deer, tufts, 

 beards and moustaches of men and the apes, are to be 

 accounted for. 



Mr. Wallace,* again, objects to Darwin's views on this head, 

 and holds that the colours of animals are not due to such 

 selection, which the more potent influence of Natural Selection 

 would neutralize. Mr. Wallace also holds that the latter will 

 not account for the condition of man.] 



Every organic being is striving to increase to its utmost, but 

 there are various checks which tend to keep each within due 

 limits, such as the supply of food, the climate, and seasons of 

 extreme cold or drought. In the years 1826 to 1828 this was 

 well shown in La Plata, where from great drought most of the 

 cattle died, and the country everywhere swarmed with mice. 

 The latter disappeared on the advent of moist weather. Again, 

 where there is abundance of food and no great check some 

 animals increase extraordinarily — for example, the Passenger 

 Pigeon and the Fulmar Petrel — yet the latter lays only one egg. 



* 1 Tropical Nature,' p. 211, &c, 1878. 



