204 THE INFANCY OF ANIMALS 



as an aid to locomotion, are provided with a fin down 

 the back. In due course, however, the fin vanishes, 

 and the fish-like stage is thrown off, the young emerging 

 on to dry land, where for the rest of their existence they 

 remain. 



Some of the salamanders are viviparous, and they pre- 

 sent some curious facts in this connection. Thus in the 

 yellow-spotted, or fire salamander, the female retires to 

 the water to give birth to her young, which range from 

 ten to fifty, of small size, and bearing gills, like larval newts, 

 but having all four limbs developed. In the other, the 

 black salamander, which lives in the Alps, at an altitude 

 of between 2,000 and 9,000 feet, the young are not born 

 till the larval stage is passed. Not more than four, be it 

 noted, are produced at a birth, and they have a remark- 

 able history, one indeed unique of its kind. In the first 

 place, a large number of eggs are formed in the ovaries 

 and escape into the uterus — that portion of the oviduct 

 wherein the development of the eggs into embryos takes 

 place ; but, as a rule, not more than one egg, and never 

 more than two, are destined to produce a salamander. 

 And this because the rest are broken up to serve as em- 

 bryonic food. Briefly, the embryo passes through three 

 stages. During the first it lies within the egg and feeds 

 upon the yolk stored therein, after the fashion common 

 to the race. The second is entered upon when it escapes 

 from this egg and feeds upon a mass of yolk formed by 

 the disintegration of hundreds of other eggs, and this 

 yolk is directly swallowed by the mouth, not absorbed 

 by the intestine as in the first stage. Whether these 

 eggs represent its potential brothers and sisters, or are 

 merely infertile eggs, produced for the sake of the yolk, 

 seems not to be known. The third stage is reached 



