140-(110) GRADATION IIST A1STIMAL LIFE. 



question. It cannot be determined except by the appli- 

 cation of many principles ; as many as our knowledge of 

 the structure and the habits will enable us to apply. 



It follows again, that we must know all the facts 

 which the most diligent observation can furnish us about 

 the life-history of any animal, before any reliable judg- 

 ment as to grade can be reached. It is again evident, 

 that such a judgment can be attained, if at all, only by 

 a careful averaging of the elements of degradation or 

 superiority in a given case ; not omitting to take into 

 account the great difference in relative value of the vari- 

 ous gradational distinctions. We must already have 

 noticed that one animal as compared with another, may 

 have several elements of superiority, and also several of 

 inferiority. Thus the owl is superior to the hawk in 

 his broad face, and the frontal aspect of his eyes, but he 

 is inferior in having nocturnal rather than diurnal 

 habits. The mole, as carnivorous, would be regarded 

 as superior to the squirrel, but his burrowing, nearly 

 sightless and sluggish habits make him, in so far, infer- 

 ior. The dolphin is far superior to the eagle, in being a 

 mammal, th^ highest class of vertebrates, and in posses- 

 sing teeth ; yet it is much inferior to the eagle as re- 

 gards its being an inhabitant of the water, (though not 

 water-breathing,) and in having the degraded form of 

 fins, in the place of legs or wings. W.e have seen that 

 the crab has elements of superiority in the condensation 

 of parts around the head, and the almost entire suppres- 

 sion of the tail-like abdomen ; but it has elements of de- 

 gradation in its facile power to replace lost limbs, and 

 in its being a water- breather, even when it aspires, as it 

 does sometimes, to live on land. 



Since the gradational relations of animals are so com- 

 plicated, biologists are little inclined in these days to at- 

 tempt anything more than very general and provisional 

 conclusions as to the relative rank of the different groups. 

 The idea of arranging these groups according to relative 

 rank, so that they will stand one over the other in a serial 

 line, has been entirely abandoned. Of the grand subdi- 

 visions of the animal kingdom, a general order of grada- 

 tion may be partially made out ; the protozoa are evi- 

 dently the lowest ; the vertebrata the highest ; the 

 articulated aainiais are higher than the coelenterata. 



