30 THE PRACTICAL FISHERMAN. 



gills of the carp (old fish especially), cannot be surpassed as an example 

 for description. To the naked eye this minute organism appears as a 

 tiny bunch or tuft of colourless filament ; and, although I have seen it in 

 comparatively large quantities on the cilia of the gill, seems not to produce 

 any marked effect on the " host " or fish. Under the microscope, how- 

 ever, it appears to be long tubes devoid of any partitions, extending in all 

 directions. By the use of high powers a circulating juice or protoplasm 

 may be seen occasionally flowing, to all appearances, in contradictory 

 and opposite directions. After about thirty-six hours this juice or 

 protoplasm seems to collect and dilate the end of the tube, and the 

 granules, of which it was composed, after being isolated from the lower 

 part of the tube in question by a rapidly-formed partition, gradually 

 assume a larger form of sexagonal shape. Eventually, by a rupture of 

 the parent cell, they are set free, and assume an oval appearance. They 

 possess a pair of wheel-like motions, and, as if living, set about seeking 

 new forms for attachment. If in a short time no appropriate "host" 

 be found, the movement ceases. They exist a considerable time in water 

 without deterioration if no suitable nidas be met with. 



Although, as I have above indicated, no prejudicial result to the 

 health of the fish seems to ensue on the growth of this parasite, yet a 

 kindred growth on the gills of young trout annually proves fatal to an 

 anormous per centage. It is well known among pisciculturists that a sort 

 of epidemic which has been colloquially termed the " gill fever " is greatly 

 to be dreaded, and always attacks the alevins of trout more or less 

 immediately after hatching by the artificial process. The first symptoms 

 are only to be perceived by the microscope. The gill cover must be 

 lifted, and very minute granule-like tubes may be seen, occupying 

 probably but a small space on the fronds of the gill, and interlacing each 

 other closely. In a few days the growth increases, and either forces open 

 the gill cover or completely penetrates it. I am inclined to class this 

 curious growth with the myxogastric fungi of De Bary, on account of 

 the similarity to some of these forms in the spread of the mycelium of the 

 organism. 



As to the origin of the disease I can offer no conjecture. Two opinions 

 are held by scientists on the relation of fungi to disease ; " some main- 

 taining," says Dr. Carpenter, " that the presence of fungi is the essential 

 condition of the disease, which originates in the introduction of the vege- 

 table germs ; others considering their presence to be secondary to some 

 morbid alteration of the parts wherein the fungi appear, which alteration 

 favours their development." In the case before us there is very little to 

 choose between these opinions, from the difficulty of determining whether 

 the origin of the outbreak is a vegetable germ, throwing off sporules, or, 



