INTRODUCTORY OBSERVATIONS. 83 



investigation. After all that has been done, much remains 

 yet to be ascertained, in the functions both of the earlier and 

 the adult state of their existence, and in the phenomena of 

 their transformation. 



The species which belong to the British Fauna are more 

 numerous than they have generally been supposed to be. Of 

 the true Frogs we have two, of the Toads two, and of the 

 Newts three, even excluding the Triton vittatus of Mr. Gray, 

 which is doubtless a variety of the common species, and 

 the British habitat of which appears to be doubtful. For 

 the accurate distinction of the known species, we are in- 

 debted to my kind and valued friend Bibron, to whom Zoo- 

 logists owe incomparably the most complete work on Er- 

 petology that has ever appeared, and to which I have had 

 previous occasion to allude. 



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