PRIMEVAL SALAMANDERS. 67 



such a high rank, since they show many signs of re- 

 lationship with fishes, all of which are quite lost in re- 

 cent reptiles. These creatures should rather be spoken 

 of as Amphibians, by which title we shall hence- 

 forth allude to them when we desire to speak of them 

 in a collective sense. Frogs and toads are likewise 

 members of the same great group, of which one of the 

 most distinctive features is that during their lives its 

 members pass through a metamorphosis thus chang- 

 ing from a purely aquatic creature (the tadpole) without 

 limbs, and breathing by means of gills like a fish, to 

 one which becomes capable of progression on land, 

 with two pairs of legs, and breathing either entirely or 

 partially by means of lungs, the gills being in some 

 cases completely lost (as in the frog), but occasionally 

 retained as subsidiary breathing organs. This change or 

 metamorphosis, we may remark in passing, is of itself 

 almost sufficient to prove the doctrine of evolution, 

 being, in fact, nothing less than the actual transforma- 

 tion, under our very eyes, of a creature a little higher 

 than a fish into one but little lower than a reptile ; so 

 little lower, indeed, that, as we have said, it popularly 

 obtains brevet rank in that group. A feature by which 

 the skull of an Amphibian can always be distinguished 

 from that of a Keptile, at a glance, is found in the 

 mode in which it articulates with the first joint of the 

 back-bone or vertebral column. Thus, in Amphibians, 

 as shown in Fig. 21, the hinder or occipital region of 

 the skull is furnished with two processes, or condyles, 

 which are received into a pair of cups in the first joint 



