The Dissection of the Fish 



29 



not be homologous with abdominal pores. In most other bony 

 fishes the testes and ovaries are continued directly into ducts 

 which open to the outside. 



Organs of Nutrition. The organs thus shown in dissection 

 we may now examine in detail. 



The mouth of the fish is the organ or series of structures first 

 concerned in nutrition. The teeth are outgrowths from the 



FIG. 17. Black Swallower, Chiasmodon niger Johnson, containing a fish larger 

 than itself. Le Have Bank. 



skin, primarily as modified papillae, aiding the mouth in its various 

 functions of seizing, holding, cutting, or crushing the various 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 regard 

 to species or condition. With the carnivorous fishes, to feed repre- 

 sents the chief activity of the organism. In proportion to the 

 voracity of the fish is usually the size of the mouth, the sharp- 

 ness of the teeth, and the length of the lower jaw. 



The most usual type of teeth among fishes is that of villiform 

 bands. Villiform teeth are short, slender, even, close-set, making 

 a rough velvety surface. When the teeth are larger and more 

 widely separated, they are called cardiform, like the teeth of a 

 wool-card. Granular teeth are small, blunt, and sand-like. Ca- 

 nine teeth are those projecting above the level of the others, 

 usually sharp, curved, and in some species barbed. Sometimes 



