266 BIOLOGY: GENERAL AND MEDICAL 



As Mr. Darwin says in the last chapter of the " Origin 

 of Species": "This whole volume is one long argument." 

 It is, therefore, difficult to give it the force it should 

 convey either through a series of excerpts, such as has 

 been here presented, or by any brief synopsis of its 

 contents. To read the book is to become impressed by 

 the worth of the argument as well as by the great array 

 of carefully chosen facts that have been collected in 

 its support. Its appearance was followed by an enthu- 

 siastic reception, and the theory of natural selection 

 is still the source of much careful examination and 

 experimentation. 



In conclusion Mr. Darwin makes the following state- 

 ment: "I am convinced that natural selection has been 

 the main but not the exclusive means of modification." 



In one of the excerpts given above this language is 

 used: " But if variations useful to any organic being 

 ever do occur, assuredly individuals thus characterized 

 will have the best chance of being preserved in the 

 struggle of life; and from the strong principle of in- 

 heritance these will tend to produce offspring similarly 

 characterized." 



If the readers of Darwin had followed his text as care- 

 fully as they should, some of the errors regarding his 

 opinions might have been escaped. It is quite clear 

 that he believed natural selection to be "the main, but 

 not the exclusive means of modification/' and it is equally 

 evident that the general statement that his theory 

 hinges upon the "transmission of acquired characters" 

 is doubtfully correct. The theory really treats of the 

 preservation of useful, and the elimination of useless 

 characters and the characters themselves appear or dis- 

 appear spontaneously i.e., as the result of the natural 

 tendency of living things to vary. 



The first effect of Darwin's work was to carry the 

 world of science by storm, but at the same time to arouse 

 intense hostility on the part of the theologians who 

 found the theory of descent, which, as has been shown, 



