Fishes . black, while inrelated forms it may be pale in color. It is more likely to beblack in fishes from deep water and in fishes which feed onplants. The Spiral Valve.—In the sharks or skates the rectum orlarge intestine is peculiarly modified, being provided with a spiralvalve, with sometimes as many as forty gyrations. A spiralvalve is also present in the more ancient types of the true fishesas dipnoans, crossopterygians, and ganoids. This valve greatlyincreases the surface of the intestine, doing away with the neces-sity for length. In the bow^n (Aniia) and the garpike (Lepi- The Dissect
Fishes . black, while inrelated forms it may be pale in color. It is more likely to beblack in fishes from deep water and in fishes which feed onplants. The Spiral Valve.—In the sharks or skates the rectum orlarge intestine is peculiarly modified, being provided with a spiralvalve, with sometimes as many as forty gyrations. A spiralvalve is also present in the more ancient types of the true fishesas dipnoans, crossopterygians, and ganoids. This valve greatlyincreases the surface of the intestine, doing away with the neces-sity for length. In the bow^n (Aniia) and the garpike (Lepi- The Dissection of the Fish sos,) the valve is reduced to a rudiment of three or four eon^volutions near the end of the uuestme. In *e s^«* ^^* the intest,ne opens into a *aea -^^ ^^^^ o^eTr iTeS: t t:U hshes and the . n»;^°t; all hshes, as in the • vertebrates the length of the ahmentary canal ,s coordinated ».thSeTood of the fish. In those winch feed upon plants the mtes-. # ^ TT,. 20 S,one-n,ll,. > ,..s,o,m, ,n, (). Family Cwpnmd^. ^ ShTSg mial tube;cles and intestines coiled about the ar-bladder. is very long and much convoluted while ^^ those jhichfeed on other fishes it is always relatively short. In thestone roller, a fresh-water minnow ) found m theSsissippi Valley, the excessively long -t-tmes ^^^^^^^^^^^veeetable matter are wound spool-fashion about the arge airbladder Tn all other fishes the air-bladder lies on the dorsalside of the intestinal canal.
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectfishes
