62 OBSEBVATIONS ON ACCLIMATISATION OF THE TRUE SALMON. 



by Mr. George Murray, of the British Museuro, at the request 

 of Professor Huxley, with the view of ascertaining what 

 influence lime in the water had in the development 

 of the disease. The results obtained were, however, to a 

 great extent of a negative character only, furnishing at the 

 most, as remarked by Mr, Murray, " starting points for fresh 

 experiments " (Annual Report of the Inspector of Fisheries 

 England and Wales, for the year 1883). To my mind, from 

 a perusal of the report quoted, the lime used in these 

 experiments was probably deficient in strength or in caustic 

 properties, or possibly, the fungus experimented with had 

 been cultivated to such an extent as to have, so to say, lost 

 its virus, or in other words its capacity for propagation. 



The actual role played by caustic lime, acids, or other 

 chemical compounds in the development of the fungus disease 

 on the epidermis of a fish appears to me to be purely 

 mechanical, and in fact identical with that exerted by hard, 

 •water on a delicate human stin. It causes it to become, as 

 it were, chafed or chapped in the fishes skin, probably 

 imperceptibly to the human vision, though at the same tiifie 

 in the form of minute raw surfaces sufiiciently large for the 

 lodgment and further development of the microscopic spores 

 of the parasitic Saprolegnia. Unless in fact there is a crack 

 or abrasion of the cuticular surface, be it however small, the 

 fungus spores may swarm in the neighbourhood without 

 exerting any ill effect whatever upon the fish. In demon- 

 stration of this proposition I may mention that at the 

 Eisheries Establishment, Battery Point, I have up to a recent 

 date kept several varieties of indigenous fish, including 

 native trout, Galaxias truttaceus, blackfish, Gadopsis 

 vnarmorahis, and the little native perch, Microperca Tasmania, 

 in tanks in which the fungus has for many months 

 past develoj)ed luxuriantly on any small fragments of 

 mussel or other animal substances used as food and 

 left for a few days at the bottom of the water 

 (Specimens exhibited"). ISTotwith standing its presence in 

 such abundance the fish have enjoyed a vigorous state of 

 health, their soimd and healthy skins, according to my 

 interpretation, affording no foothold for the attachment of 

 the parasitic fungus. Now it so happened that in recently 

 moving the boxes, slates, and other apparatus from certain 

 of the breeding troughs one of the little trout got bruised 

 upon the head, with the consequence that the fungus has 

 immediately seized upon it and its development, if not arrested, 

 will without doubt prove fatal to the fish. This specimen 

 I exhibit on this occasion and propose, should it live long 

 enotigh, to attempt its cure with a salt-water bath. ISTo more 

 fitting illustration could, I think, be given of the phenomena 



