316 LIFE AT DOWN. JET AT. 33-45. 



ments of facts in natural science, as if they were not only 

 correct, but exhaustive ; as if they might be dealt with de- 

 ductively, in the same way as propositions in Euclid may be 

 dealt with. In reality, every such statement, however true it 

 may be, is true only relatively to the means of observation 

 and the point of view of those who have enunciated it. So 

 far it may be depended upon. But whether it will bear every 

 speculative conclusion that may be logically deduced from it, 

 is quite another question. 



" Your father was building a vast superstructure upon the 

 foundations furnished by the recognised facts of geological 

 and biological science. In Physical Geography, in Geology 

 proper, in Geographical Distribution, and in Palaeontology, 

 he had acquired an extensive practical training during the 

 voyage of the Beagle. He knew of his own knowledge the 

 way in which the raw materials of these branches of science 

 are acquired, and was therefore a most competent judge of 

 the speculative strain they would bear. That which he 

 needed, after his return to England, was a corresponding 

 acquaintance with Anatomy and Development, and their rela- 

 tion to Taxonomy— and he acquired this by his Cirripede 

 work. 



" Thus, in my apprehension, the value of the Cirripede 

 monograph lies not merely in the fact that it is a very admi- 

 rable piece of work, and constituted a great addition to posi- 

 tive knowledge, but still more in the circumstance that it was 

 a piece of critical self-discipline, the effect of which mani- 

 fested itself in everything your father wrote afterwards, and 

 saved him from endless errors of detail. 



" So far from such work being a loss of time, I believe 

 it would have been well worth his while, had it been practi- 

 cable, to have supplemented it by a special study of em- 

 bryology and physiology. His hands would have been greatly 

 strengthened thereby when he came to write out sundry 

 chapters of the ' Origin of Species.' But of course in those 

 days it was almost impossible for him to find facilities for such 

 work." 



