1 88 THE INFANCY OF ANIMALS 



the frog, for internal gills, and these in turn are replaced 

 by lungs. But during the time that the external gills 

 are worn the young newt displays a curious rod-like 

 outgrowth from the side of the head which is supposed 

 to serve as a " balancer," but of its precise functions we 

 have probably still much to learn. Another curious point 

 of difference lies in the fact that in the young newt the 

 fore-legs make their appearance first : here again we ask, 

 Why ? and we have no answer to give. 



More puzzling still is the strange case of the Mexican 

 salamander commonly known as the " Axolotl," which 

 commonly never " grows up," but remains in the larval 

 stage throughout its lifetime, yet becomes sexually mature 

 and reproduces its kind ! It is an ugly creature, large, 

 heavy-looking, and black as ink. But every now and then, 

 once in a dozen years or so, one out of ten thousand of 

 such erratic larvae loses its giUs, decreases in size, and crawls 

 out on to the dry land' a yellow-spotted salamander known 

 as the Amblystoma. This is the adult form of the axolotl. 

 And, in due course, it lays eggs, and produces a swarm of 

 axolotls, and not for dozens of generations will the phoenix- 

 like amblystoma appear again ! 



Certain other salamanders present features of a no less 

 startling character. Thus in the newts of the genus 

 Desmognathus and Sferlerpes, of which we may cite as 

 examples the Red Desmognathus {Desmognathus fuscus) and 

 the Double-lined Sperlerpes {Sferlerpes bilineatus), the larvae 

 display vestigial lungs, but the adults are quite lungless and 

 breathe, according to some authorities, entirely through the 

 skin, which is always moist. According to others respira- 

 tion is performed by taking repeated gulps of air into the 

 throat and then expelling them, the blood-vessels in this 

 region absorbing the oxygen from the air thus introduced. 



