iS2 THE MAIN CURRENTS OF ZOOLOGY 



best, that is the ideally perfect, but in the survival of 

 the fittest. A similar instance is found in the sup- 

 pression of certain sets of organs in internal parasites. 

 The organs of digestion, not being necessary under 

 their condition of life, are suppressed, but the repro- 

 ductive organs, upon which continuance of the race 

 depends, are greatly increased. These illustrations 

 will assist in giving an idea of what Darwin meant by 

 natural selection. 



One other point should be emphasized. Darwin, 

 who was one of the most candid, sincere and straight- 

 forward of men, did not claim that natural selection 

 was the only natural agency but merely the chief one 

 in bringing about evolution. 



Darwin's theory met with a very different recep- 

 tion from Lamarck's. It received immediate atten- 

 tion. It was vigorously attacked and defended and 

 was ultimately accepted. The contrast was so 

 great that naturally the inquiry arises Why? It 

 was promulgated more than fifty years after La- 

 marck's announcement and, in the meantime, the 

 way had been prepared by the publication of Lyell's 

 Principles of Geology (1830), by Chambers' Vestiges 

 of Creation (1844), by Herbert Spencer's writings 

 regarding the reasonableness of the hypothesis of 



