48 AMPHIBIA CHAP. 



the sides of the throat, 'as in Rana esculenta (Fig. 52, p. 269), 

 or when the skin is thinned and converted into a bladder-like 

 pouch, as in Hyla arborea" l These sacs exhibit many modifica- 

 tions. They may be unpaired and median, and open by two slits 

 into the mouth, on either side below the tongue ; in Bufo one of 

 the slits or openings, either the right or the left, is obliterated. 

 They may be paired and symmetrical, and open one on each 

 side of the head, below and near the posterior angle of the jaws. 

 These modifications differ in closely allied species. They reach 

 their greatest complication in Rhinoderma and in some of the 

 Cystignathidae by extending far back beneath the skin into the 

 wide lymphatic spaces. In Rhinoderma they are put to the 

 unique use of nurseries for the young (see p. 228). Leptodactylus 

 typhonius has a very distinct pair of outer vocal sacs and a 

 well-marked unpaired sac which extends into the belly and com- 

 municates with each outer sac. Several species of Paludicola, 

 e.g. P.fuscomaculata and P. signifera, have a similar arrangement, 

 in addition to an unpaired gular sac which can be inflated 

 independently of the rest (see Fig. 45, p. 220). 



URINO-GENITAL ORGANS 



The kidneys and the male generative glands are still inti- 

 mately connected with each other. The general plan is as 

 follows : 



The kidneys consist of a large number of glomeruli, produced 

 by the coiled segmental tubes, each of which is composed of a 

 nephrostome or funnel opening into the body-cavity, a Mal- 

 pighian body and an efferent canal. The latter combine to form 

 the segmental duct which opens into the cloaca. The testes, 

 composed of a large number of sperm-producing glands, are 

 drained by transverse canals which combine into a longitudinal 

 canal, and this again sends off numerous efferent canals which 

 open into the efferent canals of the kidney, so that the segmental 

 duct (Leydig's duct of many authors) conveys both sperma and 

 urine. 



In the female the network of transverse and longitudinal 

 canals, which originally connect the generative glands with the 

 kidney's efferent canals, is reduced in so far as the connection is 



1 Boulenger, The Tailless Batrachians of Europe, Ray Soc. 1896. 



