54 ELEMENTARY BIOLOGY. [CHAP. 



b. The genital ducts (vasa efferentid}; delicate tubes 

 lying within the mesorchium and placing each 

 testis in communication with the inner border of 

 the kidney of the same side. 



c. The genito-urinary canal (ureter]. Cf. Sect. i. c. 



Examine the seminal vesicle (R. temporaria) 

 under a hand lens ; it will appear to be continued 

 forwards as an excessively delicate filament which 

 can be traced, within the mesentery, as far as the 

 base of the lung. Try to isolate this and follow it 

 back ; it will be found to skirt the outer border of 

 the vesicula seminalis, becoming lost in the base 

 of the ureter. 



Not unfrequently one or more watery vesicles or 

 cysts are set along the course of the above-named 

 filament. More rarely it may be wholly or in part 

 well denned and tubular, having the appearance of 

 an immature oviduct, a vestige of which it really 

 represents. 



d. The fat body (cf. Sect. B. 2. /'.). This is, in the 

 male, very large. Rarely its basal portion may be 

 swollen and pigmented, giving rise to an organ 

 (Bidder's organ] having much the appearance of 

 the ovary of the female and confluent with the 

 head of the testis. 



4. Remove a kidney and pin down under water, ventral 

 face uppermost. Carefully dissect off the mesentery 

 and examine under a lens ; its whole surface will be 

 seen to be studded by an immense number of mi- 

 nute orifices (tiephrostomes\ placing the interior of 

 the kidney in communication with the pleuro-peri- 

 toneal cavity. 



