60 



EXAMPLES OF CONNECTION BETWEEN CLASSES. 



Flo 17 ._ WATER . NEWT . 



FIG. 18. AGAMA. 



with a hard, horny skin, that reminds us of the shell of the 

 Turtle ; and we have in 



the ponds and ditches *s * ^ 



of our own country 

 more than one species 

 of the Water-newt, 

 (Fig. 17), which has 

 the/orwof the Lizard, 

 whilst, in its metamorphosis and internal structure, it corresponds 

 with the Frog. Among the Lizards, again, there is a tribe that 



is characterised by its 

 flattened body and 

 Frog-like form. One 

 species of these is seen 

 in Fig. 18 ; but there 

 are others, in which 

 the tail is shorter, and 

 the body broader, so as still more to resemble that of a Frog. 

 Thus, we have not only the connecting link of the Lizard-like 

 Frog, but of the Frog-like Lizard ; the essential characters of one 

 of the groups being preserved in each case, but displayed under 

 the form of the other. 



41. Of a complete series 

 of transitional forms be- 

 tween two classes, moreover, 

 we have a beautiful instance 

 in the case of Reptiles and 

 Fishes. One of these tran- 

 sitions is established by the 

 metamorphosis of the Frog 

 tribe already adverted to ( 18) ; but the connection is shown 

 also in certain species, which, even in their adult state, possess 

 both lungs and gills, and which have the whole of their conforma- 

 tion intermediate between that of the true Fishes and that of 

 Reptiles. Of this kind are the Axolotl (Fig. 19), which is undoubt- 

 edly a Reptile, since the characters of the Reptile predo- 



FlG, 19. AxOLOTt. 



