'26 SEALS OF THE SHETLAND ISLANDS. 



between two well-marked species. Still, this law is so uni- 

 versal, as to form the basis of a good specific character, 

 although the progress of natural history is daily add- 

 ing exceptions to it. Domestication may produce such 

 changes in the physiology of animals, as to allow of hy- 

 brids, and these to be prolific, neither of which circum- 

 stances might happen in the wild state ; and different 

 species that may occasionally interbreed in the wild state 

 (or one of the sexes in the wild with one in the tame), 

 might be subject to circumstances analogous to those of do- 

 mestication ; and farther, certain congenerous animals may 

 naturally have this boundary of specific distinction less ab- 

 solute and clear. 



In seeking for distinct characters by which to define the 

 different species of mammalia, the tendency has become very 

 general to trust implicitly in the last instance to their osteo- 

 logy, and at length characters are not considered fixed or 

 scientific until they have been osteologically pointed out. 

 The remarkable genius and sagacity of Cuvier, in his splen- 

 did and successful researches into fossil organic remains, 

 has doubtless contributed much to this extreme preposses- 

 sion, which leads so many naturalists to prefer entombing 

 themselves in the charnel-house of Nature to basking in the 

 light of her living forms. Yet, while the warmest admira- 

 tion cannot justly be withheld from that illustrious man, 

 who, from some insignificant knob of a bone, could evoke 

 from the wrecks of a world the perfect form of an extinct 

 animal, we should still rather wish to see the mastodon and 

 megatherium embodied, than have their conceptions pre- 

 sented to us only as trophies of science. To be able to steer 

 safely one's way through the chaos of organic remains, de- 

 mands not only great science and talent, but the intuitive- 

 like tact of great experience ; and here every naturalist can- 

 not hope to be a Cuvier. In this department, however, a cri- 



