DISTRIBUTION OF ORGANISMS. 165 



the scale. Nor is this merely a hypothetical view of the animal 

 kingdom. It is strongly pointed to by some of the most inter- 

 esting discoveries in embryology. It is supported by several 

 important considerations regarding the general characters of 

 particular series. It likewise harmonizes with that order of 

 fossils, which may be said to form a sort of rude outline of the 

 history of organization upon earth. Finally, such reformation 

 as this new view calls for in classifications, is accordant in its 

 general demands with all those recently 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 them in 

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

 ganization first into Vertebrata (having an internal skeleton) 

 and Invertebrata, and afterwards into such divisions as these 

 of the vertebrata namely, Mammalia, Birds, Reptiles, Fishes. 

 In these grades are comprehended animals of very various 

 character, animals which only agree in this particular of a 

 community of grade or rank. But other divisions in the 

 common classifications are into groups or series of animals 

 closely allied to each other in form, and of one general cha- 

 racter, as, for example, the cephalopoda, the echinodermata, 

 the Crustacea. The one kind of division may be said to be 

 transverse, the other longitudinal. Such a diversity gives rise 

 to a suspicion that there is something wrong, something out of 

 accordance with nature. And so it is. The true fundamental 

 divisions are entirely of the latter kind longitudinal ; there 

 only do we find persistence of characters ; the other so-called 

 divisions are only the marks of stages which the true divisions, 

 the Stirpes of being, have reached in their respective courses. 

 It is nevertheless necessary, in the meantime, to keep the ex- 

 isting classification in view, and to use its language, in order 

 that my own views may be intelligible. 



Cuvier divided the Invertebrata into three great masses, the 

 Radiata, the Articulata, and Mollusca. Of these, the two last 

 appear as co-ordinate, though distinct from each other ; while 

 the Radiata, again, may be considered as forming a kind of 

 basis for the whole kingdom. 



The RADIATA are all of them animals of exceedingly simple 



