THE CATFISH. 105 



Understand its function and the reason for its connection with the 

 oesophagus. 



h) In the hinder part of the abdominal cavity are the reproductive 

 organs, partly overlying the air bladder. The testes of the male 

 are long, depressed, grayish white structures, lobed on one border 

 and straight along the other. The reproductive elements are dis- 

 charged through a pair of tubes vasa deferentia which unite 

 before opening into the urino-genital sinus. The ovaries of the 

 female are cylindrical in form and bluntly pointed at both ends. 

 The two oviducts unite for a part of their length, like the vasa 

 deferentia, but, instead of opening into a urino-genital sinus, the 

 united ducts discharge the eggs through a separate orifice located 

 between a urinal aperture and the anus. 



i) A small urinary bladder may be located a short distance ahead of 

 the urino-genital sinus (male) or urinary papilla (female). Note 

 its connection with one or the other of these openings and also, by 

 means of the ureters, with the kidneys. The latter are long, 

 dark colored, irregular organs, partly fused together and adhering 

 closely to the dorsal wall of the abdomen. By means of a beaded 

 bristle trace the connections of the external openings with the 

 organs considered in this and the preceding paragraph. 



Exercise 7. Make a diagram of the arrangement of the urinary and 

 reproductive organs of the female, together with their ducts and ex- 

 ternal apertures. Make a similar diagram for the male. 



j) By removing the pectoral fins and the portion of the pectoral girdle 

 included between them, the cavity occupied by the heart pericar- 

 dial cavity will be exposed. This cavity is bounded posteriorly 

 by the false diaphragm. Taken together, the pericardial and 

 the abdominal cavities constitute the coelome. Note the way in 

 which the heart is protected from injury. Its four parts can be 

 readily made out: Posteriorly is the sinus venosus, a semi-trans- 

 parent enlargement of the returning blood vessels. This is pre- 

 ceded by the lobed auricle, which, in turn, connects with the 

 single ventricle, the firmest and largest division of the organ. 



