288 



ZOOLOGY 



SECT. 



(Fig. 893, St) in the form of a nodule of cartilage inserted in the 

 fenestra ovalis. In the perennibranchiate Urodeles and in the 

 larvae of the air-breathing forms lateral sense-organs are present. 

 There was an extensive lateral line system, leaving its impress on 

 the bones of the skull, in the Stegocephali. 



Urinogenital Organs. In the Urodela the kidneys (Fig. 900, 

 N) are much elongated and are divided into two portions, a broad 

 posterior part, the functional kidney (GN) t and a narrow anterior 

 sexual part connected in the male with the efferent ducts of 

 the testis. Numerous ducts leave the kidney and open into the 

 Wolffian (mesonephric) duct [lg.(Ur.)], which thus acts as a ureter 

 in the female, as a urinogenital duct in the male. The oviduct 

 [mg. (Od.)] is developed from the Mlillerian duct, a rudiment of 

 which (mg., mg'.) occurs in the male. In the Gymnophiona the 

 kidneys extend the whole length of the coelome, and in the young 

 condition are formed of segmentally arranged portions, each with 

 a nephrostome and a glomerulus, as in Myxinoids (see p. 132). 

 A pronephros is present in the larva, but disappears in the adult. 

 In some Gymnophiona the cloaca can be protruded and acts as a 

 penis. 



Reproduction and Development. External impregnation 

 takes place in Anura,but in many Urodela the sperms are aggregated 

 into spermatophores by glands in the wall of the cloaca, and these, 



being deposited on the body of 

 the female, are taken into the 

 cloaca and effect internal impreg- 

 nation. 



Several curious instances of 

 parental care are known. In the 

 Obstetric Toad (Alytcs olstctri- 

 cans) of Europe the male winds 

 the strings of eggs formed by 

 the adhesion of their gelatinous 

 investment round his body and 

 thighs, where they are retained 

 until the Tadpoles are ready to 

 be hatched. In Rhinoderma 

 darwinii, a little South American 

 Frog, they are transferred by the 

 male to his immense vocal sacs 

 and there hatched. In another 

 Anuran, Nototrema (Fig. 901), 

 there is a pouch on the back of 

 the female in which the eggs are stored, the young being hatched 

 in the adult or Frog-form. Lastly, in the Surinam Toad (Pipa 

 americana, Fig. 902) the skin on the back of the female becomes 

 soft and spongy during the breeding season : the eggs are placed 



FIG. 901. Nototrema marsupium. 



Female, with, pouch opened. (From 

 Mivart.) 



