90 CHARLES DARWIN. 



those more general laws by which it was possible to 

 understand the development of the whole animal and 

 vegetable worlds. 



There is a tremendous contrast between these two 

 discoverers, in the speed with which they respectively 

 developed their ideas on the subject into a shape 

 which satisfied them as suitable for publication. 

 Wallace, after the inspiration which followed his 

 reflections upon Malthus, had " thought oui almost 

 the whole of the theory " in two hours, and in three 

 evenings had completed his essay. Darwin, receiving 

 the same inspiration from the same source, in October 

 1838, wrote a brief account of it after four years' 

 reflection and work, and finished a longer account two 

 years later, but was not prepared to give anything to 

 the public until he was compelled to do so fourteen 

 years later in 1858. All this delay was of the greatest 

 advantage when a full exposition of the theory finally 

 came before the world in the " Origin of Species " ; for 

 all difficulties had been fully considered and answered 

 beforehand, while the wealth of new facts by which it 

 was supported compelled a respectful hearing for the 

 theory itself. 



Wallace, like Darwin, was convinced of evolution 

 before he discovered any principle which supplied a 

 motive cause for the process. This conviction is 

 expressed very clearly in his interesting essay already 

 alluded to " On the Law which has regulated the 

 Introduction of New Species " (Ann. and Mag., Nat. 

 Hist., 1855, p. 184; reprinted without alteration in his 



