THE FISH 155 



Draw reproductive organs of the specimen that you have 

 (XI). 



(6) If the fish is studied during the spawning season, 

 the entire body cavity of the female will be filled with eggs. 

 The ovaries will then have to be removed before studying 

 the alimentary canal. In this case the reproductive organs 

 should be studied first. 



(7) Back of these and above, is the urinary bladder; 

 a sir.all, pink sac. In the upper part of the body cavity is 

 the air bladder. Make a diagrammatic drawing of the organs 

 above noted, showing position. Look closely to see if there 

 is any connection between the air bladder and the stomach. 

 The air bladder is supposed to have originated from a fold 

 in the stomach or some part of the alimentary canal. 

 Scrape away the peritoneum and note the thin wall of the 

 air bladder. Do you see blood vessels in it? Remove the 

 air bladder. Of what use is it? 



(8) Above the air bladder find the dark red kidneys. 

 Trace one of the kidneys to its termination in the urinary 

 bladder. Remove all the organs studied, except kidneys. 

 Draw. 



(9) Return to the partition between the body cavities. 

 Notice again the gathering of the blood in the hepatic veins. 

 Cut carefully through it to see the heart. Remove the peri- 

 cardial membrane out to the sides. The red angular portion 

 of the heart lying hindermost is the ventricle; the darker, 

 more irregular portion lying (when in natural position) 

 above the ventricle, is the auricle. The larger blood cavity 

 back of the auricle, is the venous sinus, and the light colored 

 body in front of the ventricle is the arterial bidb. This nar- 

 rows forward into an artery which branches, one branch 



