SALMON FLIES 

 some ridicule, on account of so heretical a doctrine. It is with some 

 satisfaction, therefore, that I have received, while these pages are going 

 through the press, corroboration of my waterside observations from the 

 results of physiological research. Professor C. Hess, of Wttrzburg, has 

 communicated to ♦• Medicinische Klinik" (November 15, 1912) the result 

 of a long series of experiments which he has devoted to testing the colour 

 sense in different classes and orders of animals. This is no place to follow 

 his process of experiment in detail; briefly, the conclusion to which he 

 has come is (1) that mammals perceive light and colour in the same 

 degree as man does ; that part of the spectrum whereof the normal human 

 eye is sensitive being visible to beasts. (2) Birds in general and reptiles 

 he has found only sensitive to the colours towards the red end of the 

 spectrum; blue and violet they cannot distinguish. (3) Fishes, according 

 to Professor Hess, are quite insensible to difference of colour, perceiving 

 objects "in exactly the same manner as a totally colour-blind man"; 

 that is, variety of colour affect their optic nerves as diflferent values of 

 light intensity. Professor Hess, therefore, has arrived by a different and 

 surer road at the first of the alternative hypotheses which I, greatly daring, 

 ventured to submit to anglers, viz., that fish are either colour-blind, or, 

 possessing the colour-sense, are indifferent to it as a guide in feeding.* 



Though I adhere to my incredulity about the importance of any par- 

 ticular variety of fly to be presented to the notice of a salmon, I have by 

 no means overlooked the result of Dr Francis Ward's ingenious and in- 

 teresting observations from his subaqueous chamber as described in the 

 " Field " of May 4, 1912. His paper is illustrated with a number of photo- 

 graphs showing different salmon-flies from the salmon's point of view 

 — or nearly so, and he discusses learnedly the phenomena of refraction, 

 reflection and other agencies affecting subaqueous objects. Really, if 

 a man were to carry all these points in his head when he went a-fishing, 

 he never would get to work at all. Luckily for us all, Dr Ward has asked 

 a bed-rock question, and answered it in a way that enables us to dismiss 

 the result of his experiment as irrelevant to success, though not to science. 

 "What," asks Dr Ward, "is the appearance of a salmon-fly while 

 it is being fished ? " The answer he makes is founded upon what he saw 

 when Mr Sheringham worked a series of salmon-flies over him who was 

 ensconced in his subaqueous chamber with plate-glass sides, and that 

 answer is — " Never the same for two seconds." 



* A summary of Professor Hess's experiments and conclusions was given in The Field for February 12, 1913. 



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