102 RAMBLES OF A NATUEALIST. 



sion. This second principle, which is in some degree 

 the counterpart of the former, is not the less impor- 

 tant in zooloo-ical investio;ation. It is essential to 

 understand in what manner certain progressively 

 lower types may approximate towards some one 

 other type, since it is only by an inquiry of this kind 

 that we shall be enabled to attach any precise signi- 

 fication to the epithet inferior, which is often 

 employed in the vaguest manner. For example, 

 the mammals are unquestionably more perfect than 

 the fishes. These two types are, however, each de- 

 graded in their respective directions ; thus we have 

 higher mammals and higher Jishes as well as loioer 

 mammals and loicer jishes, and the same difference 

 of perfection is manifested in all the great divisions 

 of the animal kingdom. 



It is from a misconception of the principles which 

 we have here briefly touched upon that most of our 

 illustrious masters have fallen into grave errors. It 

 is true that we occasionally meet with expressions in 

 some of their writings which seem to imply that 

 they had confused notions of these facts ; still no one 

 had clearly demonstrated or applied them before 

 M. Milne Edwards, who has expressed himself in the 

 most explicit manner in reference to this subject 

 both in his lectures and his published works, more 

 especially in the introduction to his great work on 

 the history of the Crustaceans, If on my part 

 I have arrived at analogous results, it is certainly 

 entirely owing to the fact of my having followed the 

 example set more than twenty years ago by that 

 naturalist, and devoting myself, with the same per- 



