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 

 slowest breeding 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. 

 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 ! 



