194 



ANIMAL BIOLOGY 



been pointed out that the nephridia, which combine to form the 

 kidneys in some of the lower Vertebrates, retain their funnel-like 

 openings into the coelom and therefore afford a direct exit for 

 waste material in the coelomic fluid. It is some of these nephridia 

 which are employed in the lower Fishes for the transfer of the 

 germ cells to the outside. The testes of the male, which lie close to 

 the kidneys, become connected with the nephridia (mesonephros) 

 by a series of short delicate tubes. Through these tubes the sper- 

 matic fluid, containing the sperm from the testes, is transferred 

 to the nephridia and by them to the kidney (mesonephric) ducts 

 and so to the exterior with the urinary waste. In this way, during 



Ureter 



Urinary bladder 

 Vas deferens 



f Ureter 

 Oviduct 



Urinary bladder 

 i 



Ampulla 



of/vas 



deferens 



Seminal 

 vesicle 

 // 



- Ejaculatory 



duct 

 Prostate gland 

 --Cowper's gland 



Seminiferous 



tubule Epididymis 



Vagina 



Urethra - 



Fig. 134B. — Diagrams of the human urogenital organs. Posterior view. 



A, male; B, female. (From Hegner.) 



the period of sexual activity of the male, the kidney tubules satis- 

 factorily perform two functions, and the mesonephric ducts be- 

 come UROGENITAL CANALS. (Fig. 129, C.) 



Turning to the female, we find that the ovaries, which are sit- 

 uated in about the same position with relation to the kidneys 

 as the testes in the male, do not enter into communication with a 

 set of nephridia of the kidneys (mesonephros) ; probably because 

 the eggs are too large to pass through the tubules. Instead, what 

 appears to be the coelomic opening of a single nephridium-like 

 structure on either side (which fails, so to speak, to enter the 

 kidney complex) enlarges and becomes the funnel which connects 



