78 PRACTICAL ZOOLOGY. 



two white testes in the male. In some fishes the 

 ovary is single, in others it is double. If double, 

 the two ovaries unite in one tube, which discharges 

 the eggs — the egg-tube, or oviduct. Trace the ovi- 

 duct ; has it a separate outlet ? Sometimes the eggs 

 in the ovary can be discerned. 



7. Back of the oviduct or hinder part of the testes is a 

 small pink sac, the urinary bladder. Look for its 

 external opening back of the anus. 



8. In the upper part of the body -cavity is the air- 

 bladder. 



Make now a drawing of the organs above noted 

 in their natural positions, as seen from below. 



Look closely to see if there is any connection be- 

 tween the air-bladder and the stomach ; gently scrape 

 away the thin outer covering, peritoneum, and note 

 its thin wall ; examine the whole of this wall to see 

 if there are any blood-vessels in it. After thoroughly 

 examining, puncture and remove it. 



9. Above the air-bladder, extending along the roof of the 

 body-cavity are slender, dark red bodies, the kidneys. 

 Look for an enlargement of the kidneys in front of 

 the air-bladder ; trace one kidney to its posterior ter- 

 mination in the urinary bladder. Cut away all the 

 organs thus far studied, except the kidneys. 



10. In front of the liver is a thin partition, the false dia- 

 phragm. If this is not already opened, cut carefully 

 through it to see the heart ; also cut from the anterior 

 end of the first slit in the walls of the abdomen for- 

 ward to one side of the ventrals, through the bones 

 of the pectoral arch and on through the thick mass 

 of xuuaele, in the middle line, to the isthmus, and pull 



