n, but for our purposes the sunfish will serve as well as any. The names and location of the principal organs are shown in the accompanying figure, from Kell

shown in the sequence of dissection, leaving a

es through the abdominal cavity extending from the mouth through the pharynx and ending at the anus or vent. The stomach has the form of a blind sac, and at its termination are a number of tubular sacs, the pyloric c?ca, which secrete a digestive fluid. Beyond the pylorus ext

thin-walled reservoir, the sinus venosus, into which blood enters through the jugular vein from the head and through th

green Sunfish, Apomotis cyanellu

h lies at the base of the ventral aorta, which carries it on to the gills. After passing through the fine gill-filaments, it is returned

ir secretions through the ureter to a small urinary bladder, and thence into the urogenital sinus, a s

he spring they fill much of the body cavity and the many little eggs can be plainly seen. When mature they are discharged through the o

ever, much smaller in size and paler in color, while the minute spermatozoa appear milky rather than g

ffian duct in the male, in addition to its function as an excretory duct, serves also as a passage for the sperm, the testes having a direct connection with the kidneys. In these forms there is a pair of Müllerian ducts which serve as oviducts in the females; they extend the length of the body cavity, and at their anterior end have an opening which receives t

ans thus shown in dissection

on niger Johnson, containing a fis

ious kinds of food material. Some fishes feed exclusively on plants, some on plants and animals alike, some exclusively on animals, some on the mud in which minute plants and animals occur. The majority of fishes feed on other fishes, and without much

ardiform, like the teeth of a wool-card. Granular teeth are small, blunt, and sand-like. Canine teeth are those projecting above the level of the others, usually sharp, curved, and in some species barbed. Sometimes the canine

rot-fish, Sparisoma au

with movable teeth or teeth with serrated edges are herbivorous, while strong incisors may indicate the choice of snails and crabs as food. Two or more of these different types may be found in the same fish. The knife-like teeth of the sharks are progressively shed, new ones being constantly formed on the inner margins of the jaw, so that the teeth are marching to be lost over the edge of the jaw as soon as each has fulfilled its function. In general the more distinctly a species is a fish-eater, the sharper are the teeth. Usually fishes show little discrimination in their choice of food; often they dev

y, dentary, and pharyngeal bones. In the higher forms, the vomer, palatines, and gill-rakers are rarely wi

is always bony or gristly and immovable. Sometimes taste-buds are develop

r teeth), Archosargus probatocep

into the stomach. The intestinal tract is in general divided into four portions-?sophagus, stomach, small and large intestines. But these divisions of

loric) close together at the anterior end. In the various kinds of mullets (Mugil) and in the hickory shad (Dorosoma), fishes which feed on minute vegetation mixed with mud, the stomach becomes enlarged to a muscular gizzard, like that of a fowl. Attached near the pylorus and pouring their secretions into t

leading into the duodenum and often coalescent with the bile duct from the liver. The liver in the lancelet is a long diverticulum of the intestine. In the true fishes it becomes a lar

is found attached to the stomach in all

orsal side, as in the higher vertebrates, is called the mesentery. In many species the peritoneum is jet black, while in rela

pnoans, crossopterygians, and ganoids. This valve greatly increases the surface of the intestine, doing away with the necessity for length. In the bowfin (Amia) and the garpike (Lepisosteus) the valve is reduced to a rudiment of three or four convolutions

nesque). Family Cyprinid?. Showing nuptial tuber

very long and much convoluted, while in those which feed on other fishes it is always relatively short. In the stone-roller, a fresh-water minnow (Campostoma) found in the Mississippi Valley, th