1897] MICROSCOPICAL JOURNAL. 17 



of the adult amphibian are decidedly different from that 

 of the young: in the latter the blood is pumped through 

 gills and thence directly to the body, as in the fish so that 

 the circulation iy a *'single circulation," with the loss of 

 the gills after the maturity has been reached the double 

 circulation, and respiration as here described, are estab- 

 lished. In reptiles, birds and mammals the same is true 

 of the circulation but in their cases the single circulation 

 is confined to stages that precede free and independent 

 life, i. e,, are purely embryonic. (In some amphibia e.g. 

 Nectunis respiration is both pulmonary and branchial 

 throughout life,] 



9. The Uro-GtEnitAl System. — Cutoff and remove 

 the various viscera already examined (after making 

 drawings necessary to record the facts) taking care not 

 to damage the remaining organs in the body cavity. The 

 reproductive organs vary considerably with sex and sea- 

 son. In the breeding season the ovaries are filled with 

 black ^^^j which are greatly in the way in dissecting, 

 and the oviduct is much enlarged by the formation of the 

 large amounts of albuminous matter in which the egg^ 

 are *'laid." These latter will not of course be confused 

 with the alimentary tube by a careful dissector. The 

 paired kidneys are divided" into tWo parts: a hinder por- 

 tion of more compact texture meta-nephros, lying near to 

 the cloaca and next the doi'sal body wall; and in front of 

 this a long mesonephric part which runs forward on either 

 fiide and reaches the anterior level of the body cavity, 

 close to the dorsal body wall. There is a urinary bladder^ 

 it is thin-walled, and located below the rectum between 

 it and the body wall, in the most posterior part of the 

 body cavity. Its size varies greatly in different speci- 

 mens. Ducts {ureters) from the kidneys lead into it and 

 there is a passage urethra leading from it to the cloaca. 



The ureters pass down on the outer side of each meso- 



