138 GENERAL BIOLOGY 



leads to the mouth, and extending posteriorly to the anus 

 is the intestine. What is the shape and size of the stomach? 

 Are there pyloric coeca present? (These are small finger- 

 shaped filaments, not present in all fish.) Note the mesen- 

 tery which supports the stomach and intestine. 



3. Spleen. Observe its shape, color and position in the 

 mesentery. 



4. Reproductive Organs. The size of these organs will 

 depend upon the season, i. e., whether it be before or after 

 the breeding period. At this season they are large and may 

 fill up most of the body cavity. The testes are usually 

 whitish organs occupying a position similar to that in the 

 frog. The ovaries may vary in color and are often bright 

 yellow or orange. Determine the openings of these organs 

 in the posterior part of the body cavity. 



5. Kidney. Along the dorsal wall of the body cavity is 

 the large air bladder and just above are the tw r o kidneys. 

 The kidneys open into the urinary bladder in the posterior 

 part of the body, and this opens to the outside just back 

 of the anus. 



6. Heart. The heart is in the extreme anterior part of 

 the body. Is it in the same cavity as the other organs? 

 What is the shape, and of how many chambers is it com- 

 posed? If it is desired to trace the bloodvessels they should 

 be injected as in the frog. 



Make a drawing in side view to show the internal organs. 



7. Nervous System. This system in the fish has much 

 in common with that of the frog. The brain and cord can 

 be more easily dissected in a specimen preserved in formalin. 



8. Brain. Dissect off the skin and muscle and finally 

 the bony skull thus exposing the brain, and note: (a) the 

 cerebral hemispheres; (6) olfactory lobes; (<?) optic lobes; 

 (<f) thalamencephalon, between (a) and (c), upon which 



