Fishes. 8931 
of cartilage, skin and pigment-cells seemed to belong to smelts, but 
most of the vertebra belonged to larger fishes. The other kinds of 
food found in the stomach consisted of fragments of small fresh-water 
Crustacea, with a portion of a shrimp in one or two fishes, and an 
occasional piece of insect cuticle. 
The duodenum is generally supplied in abundance with a less 
cohesive mucts of an orange tinge, and which is continued along the 
intestine. A constant accompaniment of this mucus, in almost all 
fishes, is a number of whitish or yellowish masses, extending far down 
the gut as a fragile knotted cord surrounded by the mucus—in some 
instances nearly to the anus. When a small portion of the white sub- 
stance is put between glasses it is gritty, and is found to consist of a 
vast number of calcareous crystals like those of the triple phosphate. 
They are quite unaffected by ether, but effervesce much and disap- 
pear on the addition of hydrochloric acid. Some of the larger crys- 
tals showed roughness on their surfaces, as if smaller crystals adhered 
or had adhered to form compound masses; others had a somewhat 
radiate arrangement of the constituent crystals. They occurred in all 
portions of the intestine from the pylorus downwards, but not in the 
pyloric czca, and appeared in the fasting as well as in the full-fed fish. 
The mucus which more immediately surrounded them had a fibro- 
granular aspect. The exact origin of these crystals is an interesting 
question. So constantly were they present in all conditions as regards 
food, that they could not have been much influenced by the varying 
state of the latter. The intestinal surface being an eliminating as 
well as a secreting surface, we may conclude that these crystals had 
their origin in fluids produced by the mucus membrane. The skele- 
ton of this fish being of small specific gravity and deficient in earthy 
matter, it may be that the excessive elimination of salts keeps down 
the specific gravity; or again, the circulating fluid by this means may 
so adapt the bones to the varying density of the salt and fresh water 
that their specific gravity is in accordance with the medium. At any 
rate, and whatever be the explanation, the presence of these crystals 
is an interesting physiological fact. In a greater number of instances 
than in the case of the stomach, bones, leuses, and other dense textures 
occurred in the intestines ; for they were present in several instances 
where no trace occurred in the former, and vertebre could readily be 
detected as far down as the anus. In addition to those in which the 
débris of ascertained food in the stomach was found in the intestines, . 
I met with crustacean hairs in several instances, Diatomacee, sand- 
particles, fragments of an insect, masses of solid fat, and portions of 
