148 AFFINITIES AND GEOGRAPHICAL 



always pass from one species to another by following a de- 

 crease in perfection." " On the one hand, there are classes 

 of animals so insulated, that nothing connects them with 

 others." " On the other, there are types of organization 

 which are absolutely indivisible, and of which the most per- 

 fect beings are superior to the mean of another type, while 

 the most imperfect are inferior to it." All this is true : it 

 remained unanswered by the advocates of the development 

 theory ; and such was the position of the question when the 

 earlier editions of the present work made their appearance. 

 But the error actually lay in the original idea of a chain of 

 being. The animal kingdom (and, by consideration of parity, 

 we may presume the vegetable also) consists of a plurality of 

 series going on side by side with each other, but not all to 

 the same point in the scale. No wonder, accordingly, that 

 some appear insulated, or that the highest of some types are 

 superior to the meanest of others, while the most imperfect 

 appear inferior. Nor is this merely a hypothetical view of 

 the animal kingdom. It is clearly pointed to by some of the 

 most interesting discoveries in embryology. It is supported 

 by several important considerations regarding the general cha- 

 racters of particular series. It likewise harmonizes with that 

 order of fossils, which I have ventured to describe as not 

 something calling in itself for explanation, but a fact which 

 we may look to as one of the means of explaining something 

 else the whole history of organization upon earth. Finally, 

 such reformation as this new view calls for in our classifica- 

 tions, is accordant in its general demands with all those re- 

 cently effected by the greatest naturalists, by which external 

 and comparatively accidental characters are overlooked, and 

 only the more essential affinities regarded. If it goes beyond 

 the march of living naturalists, it goes in the direction in 

 which they are going, and over ground, to which I believe 

 they must quickly come, whether they adopt a genealogical 

 view of the organic world or not. 



The divisions of the animal kingdom, as we find it in 

 Cuvier, are partly into grades, with a regard to dignity of 

 organization first into Vertebrata (having an internal skele- 



