THE EVIDENCE FOR ORGANIC EVOLUTION 497 



ural Selection," or the " Survival of the Fittest," which he regarded 

 as an adequate cause for evolution. When a biologist speaks of 

 " Darwinism " he may, therefore, refer either to the general fact 

 of evolution, or to Darwin's theory of the cause of evolution, 

 Natural Selection. While this theory seemed adequate to most 

 biologists during the decades immediately following 1859, it gradu- 

 ally came to be regarded as a less satisfactory explanation. Many 

 criticized the theory of Natural Selection, although their convic- 

 tions regarding the truth of evolution as the historic fact were 

 progressively strengthened. 



A great deal of discussion thus arose regarding '' Darwinism," 

 that is. Natural Selection, which was held to be inadequate as 

 a cause of evolution by many competent scientific men who had 

 no intention of questioning the fact of evolution. Hearing the 

 rumblings of this controversy, many who were not scientists 

 supposed that evolution as a historic fact was being rejected, since 

 in their minds evolution and Darwinism were equivalent terms. 

 The now famous address of Professor William Bateson at the 

 Toronto meeting of the American Association for the Advance- 

 ment of Science, in 1921, is a recent illustration of this misconcep- 

 tion. Although he asserted that " our faith in evolution is 

 unshaken " — meaning by " faith," of course, a reasonable belief 

 resting upon evidence, his remarks were misconstrued as a criti- 

 cism of the general fact of evolution. What he vsaid was only that 

 we do not yet know the causes of evolution. A similar position is 

 taken by many biologists, who, nevertheless, do not regard these 

 causes as past finding out. As knowledge advances, it is hoped 

 that they may be discovered. With these preliminary explana- 

 tions, we may proceed to a discussion of the evidence for organic 

 evolution, its course, and its causation. 



The Evidence for Organic Evolution 



Outline of the Evidence. — The evidence which has led biolo- 

 gists to conclude that the innumerable species of animals and 

 plants now hving and all the species which hved in the past have 

 arisen by an evolutionary process may now be presented. In so 

 doing we shall be considering what has been called the fact of evo- 

 lution, and the course which evolution has taken in particular 

 instances. It has been explained that the fact and course of 



