CHORDA I A 



Teleostei is found in the absence of a spiral valve in the in- 

 testine in the latter group; there is one exception to this rule. 

 There are generally numerous pyloric caeca. A swimming 

 bladder (Figs. 294 and 295) is usually present, and may or may 

 not communicate by a duct with the alimentary canal. The 

 sexes are separate with one exception, but occasionally in other 

 species hermaphroditic individuals may be found ; they are, of 

 course, abnormal. In the female, the eggs in some cases pass 

 into the body-cavity, and thence out through abdominal pores ; 

 in others they pass from the body-cavity into two tubes, the ovi- 

 ducts, which open posterior to the anus ; and in still others the 

 oviducts are directly continuous with the ovary, so that the ova 

 do not enter the body-cavity at all. 



Some Teleostei are viviparous, but the majority are oviparous, 

 and the ova are generally deposited in the water, where they are 

 fertilized. In some species they sink to the bottom, in others 

 they float at the surface, others develop under the most various 

 conditions: some fishes build nests; some attach their eggs to 

 the under surface of rocks and stand guard over them ; in some 

 the ova pass into special brood pouches on the ventral side of 

 the body of the male; others develop in the mouth cavity of the 

 male ; and in one species the ova sink into the soft skin on the 

 ventral side of the female and remain there until developed. 

 Fishes generally produce an enormous number of eggs, but only 

 a relatively small percentage reach maturity, for both the ova 

 and the young fishes are the favorite food, not only of many 

 fishes, but of many other aquatic animals. 



Many fishes may be readily raised artificially, and this is done 

 to a large extent in the government fish commission stations in 

 various parts of our country. The ova are obtained from the 

 ripe female by compressing the abdomen between the thumb 

 and first finger and sliding the fingers from the anterior toward 

 the posterior end. The eggs are allowed to fall into a vessel ot 

 water, and are then mixed with the semen, or milt as it is called, 

 obtained in the same way from the male fish. The fertilized 

 gs develop rapidly in shallow trays in running water, and 

 when the young fry are sufficiently large they are transferred 

 to the open water. 



The Teleostei are very widely distributed, living in ponds, 



