16 



generally, as commonly understood) that any such 

 dogma should be propounded ; nevertheless, since all 

 analogy teaches us to anticipate it, and observation tends 

 more and more, as our knowledge advances, to corrobo- 

 rate the fact, I shall be pardoned for venturing a passing 

 thought upon a question even thus difficult of demon- 

 stration. 



Perhaps we are too prone to regard those specific 

 characters, which are so subtle that they cannot be 

 grasped by our clumsy faculties except in their broadest 

 and plainest features, as incapable of fluctuation. Yet a 

 practised eye can detect discrepancies innumerable in 

 specimens which appear absolutely alike to one that is 

 uneducated ; whilst a third person, better qualified still, 

 will trace out other and more delicate distinctions, with 

 even greater precision. And thus it is that we rise, step 

 by step, even amongst the humbler representatives of 

 the animal kingdom, to the comprehension of that great 

 truth which is so conspicuous in the nobler ones, and 

 which we have already summoned to our aid, that " there 

 is no similitude in Nature which owneth not also to a 

 difference." Let us not forget that the sphere of our 

 senses is limited; and that, although tuition will do 

 much to enlarge their capacity for perception, we are at 

 the best but a dim- sighted race : hence, we should be 

 careful to avoid conclusions which are not warranted by 

 analogy, and which our understanding, as it becomes 

 gradually brighter, no less assuredly condemns. True 

 it is, that we may not be able, as in the higher animals, 



