MAN AND LOWER ANIMALS 63 



tinued his work in that direction, investigating cranial 

 development in the chick. This subsequently led on to 

 particularly valuable and epoch-making work on the 

 classification of birds. 



Examinations and continued assistance given to Spencer 

 in the matter of proof-sheets helped to swell the enormous 

 amount of work done during the year. 



1862. 



In January, 1862, two lectures were given in Edinburgh, 

 " On the Relation of Man to the Lower Animals " (Coll. 

 Essays, vii, p. 77). — After a preliminary sketch of de- 

 velopment, the physical structure of man is compared 

 with that of the apes, and the conclusion reached that 

 there is no greater structural barrier between the two 

 than between the higher apes and ordinary monkeys. 

 Darwinism is then advanced as the only hypothesis as to 

 the origin of species " which has any scientific existence." 

 No attempt is made to slur over the provisional nature of 

 that hypothesis, the weak points in which are fully set 

 forth ; and after denial of mere partizanship Huxley 

 gives in brief the reasons which induced him provisionally 

 to accept the hypothesis : — 



" . . . . the last position in which I wish to find myself is 

 that of an advocate for Mr. Darwin's, or any other views ; if 

 by an advocate is meant one whose business it is to smooth over 

 real difficulties and to persuade where he cannot convince. 



" I adopt Mr. Darwin's hypothesis, therefore, subject to the 

 production of proof that physiological species may be produced 

 by selective breeding ; just as a physical philosopher may accept 

 the undulatory theory of light subject to the proof of the 

 existence of the hypothetical ether ; or as the chemist adopts 

 the atomic theory, subject to the proof of the existence of 

 atoms ; and for exactly the same reasons, namely, that it has an 



