444 THE ZOOLOGIST. 



diminishes first, but the gills grow until shortly before the little 

 creatures leave the water. 



The Black Salamander differs from the Spotted Salamander 

 in its uniform black colour and smaller size. It is restricted to 

 the Alps at from 2000 ft. to as much as 9000 ft. elevation, living 

 near waterfalls, or in other damp and cool situations. The most 

 interesting feature of the species is that it produces only two 

 young at a time. These are nourished at the expense of the 

 partly developed eggs in the uterus, and they undergo their 

 whole metamorphosis before they are born. Their development 

 is divided by Schwalbe into three stages : — 



(1) Still enclosed within its own follicle the embryo lives on 

 its own yolk. 



(2) Free within the vitelline mass, which is the product of 

 the other eggs, the larva feeds by taking this in at the mouth. 



(3) After the vitelline mass is absorbed, the embryo obtains 

 its nutriment from the wall of the uterus by means of gills 

 10 to 12 mm. in length. 



These two species of Salamandra are thus at once distin- 

 guished by their colour, habitat, and reproductive habits. Yet 

 even in Nature they approach one another more than has been 

 indicated so far. For the abortive eggs in the uterus increase 

 in number in S. maculosa with increasing elevation of the habitat, 

 the embryos decreasing in number and attaining a later stage 

 of development before birth. The same process can take place 

 in situations other than mountain districts if the conditions are 

 unfavourable. 



At the lower limit of S. atra an increase in the number of 

 embryos may occur, three or four being produced at a birth, 

 whilst the abortive embryos do not break up so early to form the 

 vitelline mass. In the lower habitats of S. atra examples with 

 small whitish spots are not infrequent. The yellow spots of 

 S. maculosa are most complete in regard to number, size, and 

 brightness of colouring in warm, moist localities on a clay soil, and 

 diminish in size, number, and brilliance with increasing eleva- 

 tion of the habitat. These facts suggested to Kammerer the 

 I attempt to convert one species into the other, an attempt which 

 has been to some extent successful. 



If the embryos of Salamandra atra are liberated from the 



