156 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



arranged to test the possibility of protecting the more susceptible kinds by the 

 nicest aquarium management. October 1 an expert botanist and bacteriologist, 

 already mentioned, Mr. G. P. Clinton, of the University of Illinois, thoroughly disin- 

 fected, with a strong carbolic acid solution, an aquarium tank completely isolated with 

 respect to water supply and overflow. In this tank was placed a collection of small- 

 mouthed black bass which had been brought to the aquarium especially for this 

 experiment. They had been taken in the seine, lauded with the utmost care, borne in 

 the hands to avoid surface injury, transported in an abundance of water, and were 

 when put in the tank in perfect condition in every way. They received the best of 

 care and treatment, but within two weeks the Saprolegnia appeared upon them, and 

 before another week the whole lot was practically gone with fungous disease. It 

 should be said that the aquarium filter was working badly at the time, and that more 

 than the usual number of spores doubtless entered this tank. 



As the most general result of our season's work and observations with respect to 

 the relative susceptibility of the various species of fishes handled by us during the 

 summer, it appeared that native vigor of constitution .and adaptation to a life of 

 confinement were the most important elements of a capacity to resist fungous attack. 

 The spores sprout abundantly in the surface slime of fishes of every description, but 

 their filaments seem to penetrate the skin of certain species only, and of many of these 

 only under special conditions. The most susceptible fishes on the whole were the 

 active game fishes, whose imprisonment in our small aquarium tanks seemed to work 

 too great a change in their habit of life to keep them in perfect health. Among these 

 it was not an uncommon thing for a considerable group to remain in a tank by them- 

 selves for a long time without the appearance of any fungous disease, but later to go 

 almost all at once, as if they had finally succumbed through a gradual weakening of 

 their vitality under their prison life. Ou the other hand, many kinds susceptible at 

 first, and even seriously attacked, would rally presently, after they had become accus- 

 tomed to confinement, and especially after they had began to feed. 



Among the most susceptible fishes were the large-mouthed black bass, crappies 

 (both species, but especially the paler), the white bass, the yellow bass, the pike-perch, 

 the yellow perch, and the tooth herring. The sand pike or so-called jack salmon 

 was scarcely less liable to the disease, and the warmouth suufish was also frequently 

 attacked with fatal effect, The lake trout and grayling were occasionally killed by 

 this fungus; the common pike became liable to it if left long in confinement; and the 

 common species of redhorse, and the stone-roller, though lasting frequently for weeks, 

 would eventually drop off one by one. The common sucker and the buffalo were 

 rarely infested after they had begun to eat. The forked-tail cat, the mud cat, the 

 common bullheads, and the marbled cat, rarely suffered at all; on the other hand, 

 the yellow catfish (Ameiurus natalis) was often severely attacked. The sheepshead 

 or white perch appeared usually somewhat delicate; but three specimens, among 

 the earliest of our fishes to arrive, lived the whole season through. The spoonbill 

 [Polyodon) — never before kept in an aquarium for any length of time — lived with us 

 for months with an occasional appearance of saprolegniaceous fungus on bruised 

 surfaces, especially at the tip of the snout, but perished, if at all, from lack of its native 

 food, which is of a character not to be supplied to it in our tanks. Rock bass, trout, 

 bream, and the suufish species generally, except those already mentioned, were not 



