THE FISH. 77 



gullet into the stomach, to determine its shape and 

 extent. When the stomach ends blindly behind, the 

 intestine arising from its front end, the stomach is 

 said to be caecal. Compare the stomachs of, the 

 perch and sucker. Observe a branch of the pneumo- 

 gastric nerve distributed over this side of the stomach. 



3. Find a large tube arising from one side of the stomach, 

 the intestine. In many fishes there are at or near 

 this point several worm-like branches, often matted 

 together by fat. Rest the fish on its back, and turn 

 the liver to the left, to examine these. Clear away 

 this fat, separate these tubes and count them. They 

 are pyloric caeca. With scissors make a small hole 

 in the end of one caecum ; insert the point of a blow- 

 pipe and inflate it. 



4. Just beyond the caeca, on the posterior surface of the 

 liver, is a thin-walled sac, of a greenish or yellowish 

 color, the bile-sac. When empty, it has a worm-like 

 appearance. Snip it open with the scissors, or prick 

 it with a dissecting needle to see the bile. 



5. Trace the intestine to the anus, observing that it is 

 held in place by a thin, transparent membrane, the 

 mesentery; observe the blood-vessels in it; tear this 

 away in following the intestine; find a small, deep red 

 body near the intestine, the spleen. Compare the 

 length of the intestine in the perch or bass with that 

 of a sucker. The sucker eats vegetable matter, and 

 may be called herbivorous ; while the perch and bass 

 feed chiefly on other fishes, and are carnivorous. 



6. In the hinder part of the body-cavity are the repro- 

 ductive organs; the yellow ovary (varying greatly 

 in size, according to the season) in the female, the 



