18 PROCEEDINGS OF SOCIETIES. 



I had them in every stage — gold, silver coloured, and white, and also dull brown. 

 On the 28th of January, 1856, 1 first noticed that two of tliese fish each had an ex- 

 tremely beautiful white tuft, resembling somewhat the api>earance of common 

 mould, upon their side. The extent of this patch of vegetation was not more than 

 the size of a spangle. The fish were swimming about briskly, and appeared in 

 perfect health ; and I am certain there could not have been any extent of this plant 

 — at least sufficient to be visible to the eye — present upon them twenty-four hours 

 previously. I instantly isolated the two attacked for observation, washed out the 

 jar, and placed the other fish in it. They were still to all appearance healthy 

 to the most minute scrutiny. In the course of twelve hours more the plant had 

 rapidly extended in the two fish, occupying fully twice as much of the surface as 

 it did in the morning, and next morning (24 hours) it had spread over more 

 than half the body, reaching from the nose to the ventral aperture. One was com- 

 pletely dead at ten a.m., and the other died early next day (30th January). As the 

 plant extended over their bodies they appeared to be stiff, and swam as if moving 

 with difficulty, seeking the top of the water ; they afterwards seemed unable even 

 to do this, sank to tlie bottom, and lay there sluggishly on their sides or in their 

 usual positions. Previous to this one of them appeared for a time to become top- 

 heavy, his head sinking down so far as to threaten to turn him completely round 

 on his back, and he made great and evidently painful efforts to regain his usual 

 level position. After death the plant still continued to grow over their bodies, 

 developing on the snout and over the mouth, and on the fins and tail. After a 

 few days the plant manifested itself amongst others of the fish in rapid succes- 

 sion, upwards of half of them dying within twenty days from its first appearance 

 amongst them (the minnow escaping Its ravages'). Those that last died presented 

 visibly merely the appearance of white films extending over their bodies and dang- 

 ling from their fins and tail, and did not develop during life the full- 

 grown plant with its tubuli, although in some it became sufficiently evi- 

 dent after death, and reached its perfect state and formed its zoospores. On 

 most of those attacked at this time I noticed red bruise-like marks behind 

 the gills, and especially upon the lower jaw, and in some also on the 

 upper ; similar appearances occurred around the ventral aperture, and in two or 

 three upon the sides ; but these first attacked did not present such appearances, nor 

 did those which died more recently. When attacked, my attention would usually be 

 attracted to them by their rising to the top of the water and swimming in a peculiar 

 uneasy manner, as if stiff or pained as they attempted to move, afterwards they 

 became more and more languid and sank to the bottom, breathing at longer intervals 

 than in health and irregularly, and dying usually as if suffocated, with their gill 

 covers widely distended and the gills visible. 1 may here state that I examined these 

 fish most carefully after death, their gills especially ; the most external of the bran- 

 chiae were in parts loaded with masses of germinating spores of the plant, which 

 evidently had the effect of destroying their structure and disintegrating them, strip- 

 ping off the fine lobed capillary processes from the denser cartilaginous structure, 

 and finally loosening the cartilages and necrosing them. The developed plant con- 

 sisted of very fine fibres, forming dense interlacing masses, which somewhat resem- 

 bled the fine nap on velvet. The fibres were of rather tough consistence. Those I 

 at first obtained were straight and unbranched, afterwards I found a branched con- 

 dition equally common. The tubuli contained an amorphous mucilaginous fluid, 

 with masses of globules, aggregated in very unequal amount in vaiious parts — the 

 larger were evidently oil spots, and almost filled the diameter of the smaller tubes ; 

 others were more minute, and multitudes were so small as merely to present the 

 appearance of the finest dots — these distinctly exhibited "Brown's movements" — 

 and in some instances I had fine views of the more perfect circulation, termed " cy- 

 closis." The tubuli rarely had partitions ; they ended when sterile in blunt tops, 

 gradually tapering upwards, and in oval capsules when fertile. I could trace all the 

 stages of the formation of these capsules. First the granular matter developing more 

 densely at the upper part of the tube than elsewhere, so as to give it a distinct 

 brownish colour, the top then becoming dilated into an ovoid form, and the granular 

 matter still thickening and becoming separated from the ordinary contents of the 

 tube, and the septa rapidly forming by the inflexion of the utricle. Afterwards, 



