154 THE MAIN CURRENTS OF ZOOLOGY 



arrived independently at the idea of struggle in 

 nature, with the survival of the fittest through 

 natural selection. He communicated these ideas to 

 Mr. Darwin in 1858, and, with high-minded gen- 

 erosity, Darwin was disposed to allow the credit to 

 go to Mr. Wallace, withholding his own publication 

 upon which he had been working for so many years. 

 He was pursuaded to leave the matter in the hands 

 of two of his friends, Sir Charles Lyell and Joseph 

 Hooker, who arranged for the publication simulta- 

 neously, of manuscript sketches of Darwin, made in 

 1839, 1844 and 1857, and the essay of Wallace pre- 

 pared in 1858. Although Darwin was so punctilious 

 about having his friend, Wallace, receive a share of 

 the credit, Wallace himself has insisted, and the 

 world has recognized, that the credit for the natural 

 selection theory belongs essentially to Darwin. 



Weisrnann. The theory of Weismann is more 

 complex and is difficult to state with brevity and 

 lucidity. It will dispel a wide-spread confusion 

 regarding his theory to say, at once, that he is a 

 Darwinian the recognized leader of the Neo- 

 Darwinians. He carried the idea of natural selection 

 further than Darwin did, extending it to the tissues 

 and even to the minute vital elements of the cell. It 



