302 LITE OF PROFESSOR HUXLEY CHAP. XII 



appreciate, namely, the impossibility of man's fisheries 

 affecting the numbers of the herring to any appreci- 

 able extent, a year's catch not amounting to the estim- 

 ated number of a single shoal ; while the flatfish and 

 cod fisheries remove many of the most destructive 

 enemies of the herring. Those who had not studied 

 the question in this light would say that " it stands 

 to reason " that vast fisheries must tend to exterminate 

 the fish ; apropos of which, he made his well-known 

 remark, that in questions of biology "if any one tells 

 me ' it stands to reason ' that such and such things 

 must happen, I generally find reason to doubt the 

 safety of his standing." 



This year, also, he began the investigations which 

 completed former inquiries into the subject, and 

 finally elucidated the nature of the salmon disease. 

 The last link in the chain of evidence which proved 

 its identity with a fungoid disease of flies, was not 

 reached until March 1883 ; and on July 3 following 

 he delivered a full account of the disease, its nature 

 and origin, in an address at the Fisheries Exhibition 

 in London. 



In 1881, then, at the end of December, he went to 

 North Wales to study on the fresh fish the nature of 

 the epidemic of salmon disease which had broken 

 out in the Conway, in spite of being in such bad 

 health that he was persuaded to let his younger son 

 come and look after him. But this was only a 

 passing premonition of the breakdown which was 

 to come upon him three years after. 



