314 GENERAL BIOLOGY 



form of natural transmutation, we may ask what 

 explanation has science to offer of the method of 

 their appearance ? Speaking generally, two different 

 answers have been offered to this question : That of 

 Lamarck, and that of Darwin. 1 



Darwinism. The Darwinian theory of the origin 

 of species rests upon three generalizations. First, 

 in every species of animal and plant, even the very 

 sloweljtrbreeding one, there is produced an enor- 



! mously greater number of individuals than can 

 possibly find food or foothold. Some of these, of 

 course, survive as the persistent species, the rest 

 perish. 2 This is the famous " struggle for existence," 

 from which few, if any, individuals are exempt. 



i Secondly, the fact of variation, which has already 



/ been discussed, calls to mind that in this horde of 



/ individuals every possible sort of variation will be 



found. Some of these will be favorable to survival, 



others a handicap; obviously, when competition is 



so fierce, the chances are strong that the individuals 



which possess the unfavorable variations should go 



down before those endowed with the favorable ones. 



For example, a slight difference in the speed of an 



1 Some would add also De Vries' theory of Mutation, mentioned in 

 a previous chapter. 



2 An ordinary mosquito hatching from the egg reaches maturity and 

 lays her own eggs ten days afterward. A single female lays about four 

 hundred eggs, half of which become females. If a single female should 

 hatch on April first and lay her quota of eggs ten days later, on July 1, 

 ninety days later, if all lived the progeny would number 102,914,592,- 

 864,480,008,004,001 mosquitoes ! 



