EMBRYOLOGY AND CLASSIFICATION. 301 
furnishes us with a classification, to establish 
which needs no arbitrary interference on the 
part of the naturalist, since it is founded upon 
natural evidence, both embryological and zodlogi- 
cal. While this is so obvious and easy among 
Batrachians, I have no doubt, from the scanty 
investigations I have already made, that Embry- 
ology will in the end furnish us with the means 
of recognizing the true affinities among all ani- 
mals, and of ascertaining their relative standing 
and normal position in their respective classes 
with the utmost degree of accuracy and precision ; 
. but, before this can be done, we must be as fa- 
miliar with the different stages of growth of the 
young animals of all classes as we already are 
with those of Batrachians, and shall probably 
have to push our researches in directions not yet 
dreamed of. 
Without entering into any details upon this 
subject, I may as well state here, that among 
Fishes I have lately discovered metamorphoses 
as extensive as those known to take place among 
Reptiles. Pisciculture being carried on upon 
so large a scale in some parts of Europe, it is 
surprising that the fact should not have been 
ascertained long ago. This is perhaps owing to 
the circumstance, that these metamorphoses be- 
gin after the hatching of the young, at a time 
when they are apt to die if reared in close con- 
