"Although I searched with diligence and care in the neighboring streams and waters around the Yellowstone Lake, I was unable to find any other species of fish except the salmon-trout; their numbers are almost inconceivable; average weight, one pound and a half; color, a light-grey above, passing into a light-yellow below; the fins, all except the dorsal and caudal, vary from a bright-yellow to a brilliant orange, they being a dark-grey and heavily spotted. A curious fact, and one well worthy of the closest attention of an aspiring icthyologist, is connected with these fish, namely, that among their intestines, and even interlaced in their solid flesh, are found intestinal worms, varying in size, length, and thickness, the largest measuring about six inches in length. On cutting one of these trout open, the first thing that attracts your attention is small oleaginous-looking spots clinging to the intestines, which, on being pressed between the fingers, break and change into one of these worms, small, it is true, but nevertheless perfect in its formation. From five or six up to forty or fifty will be found in a trout, varying, as I said before, in size, the larger ones being found in the solid flesh, through which they work their way, and which, in a very short while, becomes almost putrid. Their number can generally be estimated from the appearance of the fish itself; if many, the trout is extremely poor in flesh, the color changes from the healthy grey to a dull pale, it swims lazily near the top of the water, losing all its shyness and fear of man; it becomes almost savage in its appetite, biting voraciously at anything thrown in the water, and its flesh becomes soft and yielding. If, on the other hand, there are few or none, the flesh of the fish is plump and solid, and he is quick and sprightly in all his motions. I noticed that it was almost invariably the case when a trout had several scars on the outside of his body that it was free from these worms, and I therefore took it for granted that the worms finally worked their way through the body, and the flesh, on healing up, leaves the scars on the outside; the trout, in a short while, becomes plump and healthy again. The only way that I can account for the appearance of these worms is, that the fish swallows certain bugs or insects, and that the larvæ formed from them gradually develop into the full-grown intestinal worm. But even if this explanation of their appearance was received, does it not seem a little strange that while all the fish above the Upper Falls are more or less affected by them, that below and even between the Upper and Lower Falls such a thing as wormy trout is never heard of? Being unable, with my limited knowledge of icthyology, to arrive at any definite conclusion in regard to their appearance, I submit the above facts to those who are more learned than myself in this most interesting branch of natural history."