238 



lunar valves guard the opening from the ventricle into the 

 conus. The conus contains a spiral valve, and is separated 

 by valves from the very short ventral aorta. 



The ventricle receives impure blood (from right auricle) 

 and purified blood (from left auricle) into its right and left 

 regions respectively, the blood mixing to some extent 

 about the middle. The conus arises from the right side 

 of the ventricle ; consequently, when the ventricle con- 

 tracts, it is the impure blood which is driven first into the 

 conus, and it flows mainly into the pulmo-cutaneous arches. 

 When these are filled, the conus contracts, causing the 

 spiral valve to be so placed that the succeeding mixed blood 

 passes into the systemics. The remaining pure blood is 

 driven into the carotids. 



How does the Frog breathe ? 



By lungs (see pages 212, 233) ; and by the skin, when 

 hibernating in mud under water. The larva breathes at 

 first by the skin, and later by gills. 



Give a Description of (I) the Excretory, and (2) the Repro- 

 ductive Organs of Rana. 



(1) The two flattened oval kidneys are attached to the 

 dorsal body wall, one at each side of the urostyle ; and on 

 the ventral surface of each there is an elongated yellowish 

 adrenal gland. The ureters (Wolffian ducts), which arise 

 from the outer sides of the kidneys, open separately into 

 the cloaca, opposite the opening of the cloacal bladder. 



(2) The male organs, two ovoid testes, have several short 

 vasa efferentia leading into the kidneys. The ureters 

 function as vasa deferentia ; and each has, near the cloaca, 

 an associated pouch-like vesicula seminalis. 



The female organs are large folded ovaries. The oviducts 

 (Miillerian ducts) are long and coiled; the wide terminal 

 portions open into the cloaca, the narrow front portions 

 open (coelomic funnels) beside the bases of the lungs. Tho 

 ova are discharged into the body cavity, and enter Mio 

 coelomic funnels. Attached anteriorly to the tostos and 

 ovaries there are yellow and lobed fatty bodies. 



