16 GUIDES FOR VERTEBRATE DISSECTION 



oval in outline and dark-colored. Resting on each is a rounded 

 yellow body, the testis, attached only by its medial border. Each 

 testis bears a number of yellow finger-like bodies, the fat bodies 

 or corpora adiposa. Tip one of the testes toward the median line 

 and see, on the ventral surface of the mesonephros, a long band- 

 like structure, bright yellow in the fresh specimen, the suprarenal 

 gland. The deferent duct (Leydig's duct) leads back from the 

 lateral margin and hinder angle of the mesonephros. Trace 

 those of the two sides back to their entrance into the cloaca. 

 Do they unite before entrance? Do you find an enlargement 

 (seminal vesicle) on them? 



Sketch the organs. 



Examine more closely with hand-lens and note the renal and 

 genital (spermatic) arteries and veins entering and leaving the 

 kidneys and testes on the medial side. How are the fat bodies 

 supplied? Then turn one of the testes to the median side and 

 see the fine vessels (vasa efferentia) passing from the testis into 

 the mesonephros. Are they connected longitudinally? Sketch 

 these relations. 



In the female the lobulated ovaries, enormous in size and 

 crowded with eggs, are prominent on either side, especially near 

 the breeding season. Without tearing see that each ovary is 

 attached to the dorsal body wall by a thin membrane, the meso- 

 varium, in which .the ovarian arteries and veins run. In front 

 of the ovary look for the fat body. Is this attached to the 

 ovary? 



Cut into the ovary ; is it solid or hollow? Sketch the sec- 

 tion showing the relative position of the eggs. 



Remove the ovary from one side, exposing the oviduct (Mtil- 

 lerian duct), a greatly contorted tube extending the whole length 

 of the peritoneal cavity. Trace it backwards. Does it com- 

 municate with the cloaca or does it open directly to the exterior? 

 Is it free during most of its course, or is it supported from the 

 body wall? Is any part expanded to form a thin-walled uterus? 

 Trace it forward, removing the stomach and liver if necessary 

 to see its anterior end. Do tue tubes of the two sides unite? 

 Do you find one or two anterior openings (ostium tubae) ? 



Remove the oviduct. Do you find any tube connected with 

 the kidney comparable to Leydig's duct in the male (Wolffian 

 duct)? What differences can you recognize? Slit open the 



