THE REPRODUCTIVE ORGANS. 97 



i. Into the cloaca open the large intestine, the ureters, 

 and the bladder. 



ii. The bladder is a thin-walled bilobed muscular sac, 

 lying on the ventral surface of the large intestine 

 and cloaca, its two lobes communicating freely 

 with each other. It is invested by peritoneum 

 and attached to the sides of the body by special 

 peritoneal folds. 



Inflate the bladder with a blow pipe inserted through the cloacal 

 aperture : pass a seeker up the cloaca to determine the exact 

 position of the opening from the bladder to the cloaca. Cut up 

 the cloaca along one side ; wash out its contents and examine the 

 opening into the bladder. 



iii. The ureter or vas deferens is continued behind 

 the vesicula seminalis as a very short tube, open- 

 ing into the dorsal wall of the cloaca almost 

 exactly opposite the opening of the bladder on 

 the ventral surface. The openings of the two 

 ureters are close together on the apices of two 

 small papillae, overhung by a slight valvular pro- 

 jection of the mucous membrane of the cloaca. 

 iv. Remove a small piece of the testis ; place it on a slide 

 in a drop of salt solution ; press it slightly ; cover 

 and examine with a high power to see the sperma- 

 tozoa. 



B. The Female Frog. 

 1. The Reproductive organs. 



Dissect as in the male. 



i. The ovaries are a pair of black masses lying in 

 folds of the peritoneum ventral to the kidneys, 

 in very much the same position as the testes in 

 the male. Their shape, colour and size vary much 

 at different seasons of the year. On their surfaces 

 are numerous rounded projections, like small 

 shot ; these are ova in various stages of develop- 

 ment ; the smaller and younger ones are white ; 

 the larger and more mature ones black in one 

 half and white or yellowish in the other. Each 



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