EVOLUTION 201 



Biologists of all countries and thinking men of all walks in life 

 were drawn into the controversy. Living nature was searched 

 everywhere for evidence bearing on evolution. Habits and 

 instincts, coloration and mimicry of animals, living and fossil 

 forms were studied minutely in the search for proof, and little 

 by little, with the accumulation of facts the opponents of evolu- 

 tion were won over until finally the conception of evolution 

 was universally accepted as the explanation of the origin of 

 modern types of living things. 



In the meantime, however, another controversy arose, this 

 time among biologists themselves who, having accepted what 

 has taken place through evolution, did not agree as to how it 

 has taken place nor in regard to the factors involved. Darwin 

 believed that natural selection by which those organisms best 

 adapted to survive in the struggle for existence, would continue 

 to live and breed, was the chief means of the origin of diverse 

 types, although not the only means. Some biologists, following 

 Darwin believed that his process of natural selection is itself 

 the source of variations and the means of perpetuating them 

 after adaptations had arisen, useful adaptations being selected 

 and conserved, useless adaptations being a hindrance would 

 lead to extinction. Still other biologists could see little basis 

 for the origin of variations on Darwin's theory of natural selec- 

 tion and turned back to the view advocated by Lamarck in 1815 

 to the effect that animals may become changed or adapted to 

 conditions of their environment during their individual lifetime 

 and then transmit such acquired changes or adaptations to 

 their offspring. These Neo-Lamarckians thus believed in the 

 inheritance of acquired characteristics, which Darwin himself 

 believed might play some slight role in the origin of species. 



One effect, in large part of this controversy among biologists 

 was to introduce a new method of research in biological science, 

 and experimental biology grew up. At first animals were 

 mutilated in various ways to see if such mutilations would have 

 any effect upon the offspring. The failure of such experiments 

 was no check upon the use of the experimental method which in 

 the different fields of experimental zoology, botany, embryology 



