JLeoT. I.] PRIMARY AMPHIBIA. 9 



Duckbill, but wHcli I have in vain sought for in 

 any other type. My second reason is this, namely, 

 that the extremely wide range of structure taken by 

 each individual of that species, and indeed, of all its 

 kindred, from the time of hatching to the time when the 

 permanent adult form has been reached, is such as to 

 suggest almost limitless possibilities in the development 

 of the Vertebrata, so that my thoughts run almost 

 unconsciously parallel with the suggestions so ably put 

 by Professor Huxley, in his paper. I can, and do 

 imagine a group below the Prototheria, their root-stock, 

 which may well be called " Hypotheria," or creatures 

 under the beasts. 



That these were akin, closely akin, to the primary 

 Amphibia, there is every reason to believe. If they 

 were metamorphic, and that I think is very probable, 

 they lived in their infancy in the water, and their 

 respiration was aquatic. 



Our present work, however, is not to stand peering 

 down into those dark depths, but to see whether the 

 stages of the existing Prototheria will not show us many 

 instructive facts. Yet even here we are almost as poor 

 in embryos of these types, as we are in their fossils ; and 

 the present destruction of these invaluable types, for the 

 sake of mere museum exhibition, painfully suggests their 

 probable early extinction. 



The Eoyal Society, however, has lately, with great 

 liberality, furnished certain scientific Knights m.th means 



