508 THE GENERAL PRINCIPLES OF ZOOLOGY 





added interest to the writings of Herbert Spencer (1820-1903), 

 who was one of the few outspoken evolutionists of that period. 



Thus by the middle of the century a vast amount of accurate 

 knowledge in zoology had been accumulated ; theories had been 

 proposed to account for the resemblances and differences of ani- 

 mals ; and while some naturalists and philosophers held to the 

 theory of evolution, the general belief was in the theory of special 

 creation ; in fact, a scientist was apt to be considered not quite 

 sound in judgment by his colleagues, if he proclaimed himself an 

 out-and-out evolutionist. It was into such influences as these 

 that Charles Darwin ( 1809- 1882) came. A short course of study 

 at the universities of Edinburgh and Cambridge was followed 

 by the most important event in his early life, the voyage of 

 H.M.S. Beagle (1831-1836), on which he sailed as naturalist, cir- 

 cumnavigating the globe. During this time he was still a special 

 creationist, but the broad knowledge of natural history gained 

 from visiting so many new countries clearly raised doubts in his 

 mind as to the correctness of the older theory, and we find him 

 on his return in 1837 undertaking a systematic study of variation ; 

 to use his own words : " I worked on true Baconian principles. 

 and without any theory collected facts on a wholesale scale, mure 

 especially with respect to domesticated products, by printed in- 

 quiries, by conversation with skillful breeders and gardeners, 

 and by extensive reading." The idea of natural selection first 

 occurred to him in the following year, but he did not write out his 

 theory until 1844, and even then did not publish it ; for he received 

 no encouragement to do so from scientific friends with whom he 

 discussed his views. Me continued the same line of study, and 

 in 1858 received from his friend Wallace ( [822 > a recently com- 

 pleted manuscript, in which theories almost precisely like his own 

 were expressed. Then through the influence of friends Darwin 

 was induced to publish an abstract of his manuscript of 1844. in 

 the same periodical with the manuscript of Wallace. In the 

 following vear, 1859, the "Origin of Species" was published, and in 

 the course of the succeeding twenty years converted the entire 

 scientific world to the theory of evolution. In 1858 both Darwin 

 and Wallace believed that natural selection was the only fa 

 in the evolution of species ; later in life Darwin came to believe 

 that while it was the prime factor, yet use and disuse were also 



