XIV 



SPENCER'S CONTRIBUTIONS TO BIOLOGY 



SEVEN years before the publication of the Origin 

 of Species, Spencer published two biological essays, 

 in one of which, The Development Hypothesis, he 

 supported the theory of organic evolution, and in 

 the other, The Law of Population, expressed his dis- 

 covery of the missing half of the truth announced 

 by Malthus in 1798. The Principles of Biology, 

 the second instalment of the synthetic philosophy, 

 appeared in the years 1864-1867. In this chapter 

 I desire to note those particular views of Spencer, 

 the philosophic biologist, which are accepted as 

 part of biological theory to-day. His Law of 

 Population, however, is so important from a higher 

 than the purely biological point of view that it 

 will not be discussed here. 1 



The Principles of Biology is a very long, very 

 solid, and very expensive work, and we may guess 

 that the publishers, who have now begun to issue 

 the volumes of the synthetic philosophy in cheaper 

 form, will defer these volumes to the last. Never- 



1 See chapter, "The Grounds of Rational Optimism." 

 J 54 



