XIII.] THE FKOG. 191 



in front of the anterior ends of the kidneys 



their form. 

 /S. The duets of each testicle (vasa efferentia) enter 



ing the inner border of the kidney of the sam^ 



side in order to communicate with the genito 



urinary canal (9. a). 

 7. Remove the testes : open one and press ou 



some of its contents upon a slide and mount ii 



common water: examine with i objective. 

 The spermatozoa: bodies provided with ; 



small oval head and a long vibratile tail in It 



esculenta : in B. temporaria the oval head i 



absent : their movements. 



h. In the female. 



a. The ovary: an organ varying much in siz^ 

 with the season of the year. The numerou 

 ova in it. 



/S. The oviduct: a convoluted tube, not con 

 tinuous with the ovary, and running back ti 

 open into the cloaca. The greater part of thi 

 oviduct is opaque and glandular ; the part nea 

 the cloaca however is dilated, thin-walled anc 

 transparent. The oviducts open on the pos 

 terior wall of the cloaca a little anterior to th( 

 openings of the ureters. 



11. Tlie mouth, oesophagus, and respiratory organs, 



a. Open the mouth : note on its roof near th( 

 front the two hinder openings of the nasa 

 cavities {posterior nares); farther back, the twc 

 larger openings of the Eustachian recesses; th( 

 long tongue in the floor of the mouth ; fixed b^ 

 its front end to the lower jaw; its free, bifid 

 end turned towards the throat. 



