120 URODELA 



CHAP. 



second stage the yolk is directly swallowed by the mouth. 

 The walls of the maternal uterus are rather red. The ex- 

 change of nutritive fluid takes place through the long external 

 gills, which thereby function in the same way as the chorionic 

 villi of the Mammalian egg. Each gill contains a ventral artery 

 and a dorsal vein, each of which looks like the midrib of a pinnate 

 leaf; there is also a fine nerve and a weak bundle of striped 

 muscular fibres. Each gill -filament receives a capillary artery 

 which extends to the epithelium of the tip, where it turns 

 into a capillary vein. The epithelium of these filaments, which 

 are full of blood, is ciliated, the resulting current being directed 

 from the base towards the tip. In older larvae this ciliation 

 becomes restricted to the tips. The body of the gills is furnished 

 with flat epithelium, these non-ciliated portions alone are closely 

 appressed to the uterine wall, and it is here that the exchange 

 of gas takes place between mother and larva. The nutrition 

 takes place through the gills, as they are bathed by the yolk- 

 mass. 



Schwalbe also explains the whole question of the reduction 

 of the number of embryos. He says rightly that in JS. maculosa, 

 which gives birth to many young, there are in the oviduct many 

 eggs which have only partly developed into embryos, and these, 

 perhaps from want of room and nourishment, degenerate into the 

 irregularly shaped whitish -yellow bodies which are occasionally 

 found packed in between the developing embryos. Consequently 

 all those eggs had been fertilised near the ovaries. S. atra exhibits 

 a further stage in so far as most of the eggs, fertilised above in the 

 oviduct, degenerate, and only two or three become fully developed. 

 These few embryos live on the degenerating eggs, which together 

 produce the vitelline material spoken of above. The two full- 

 grown and metamorphosed embryos, each measuring about 50 

 mm. in length, are equivalent to the numerous new-born larvae 

 of S. maculosa, especially if the smaller size of the adult Alpine 

 Salamander is taken into consideration. 



Mile, von Chauvin l has experimented with the unborn larvae 

 of this Salamander. She cut out 23 larvae and put them into 

 water. One of them, already 43 mm. long, took earthworms 

 on the next day, and the beautiful long, red gills became pale 

 and shrunk, and on the third day were cast off close to the 



1 Zeitschr. wins. ZooL xxix. 1877, pp. 324 f., pi. xxii. 



