44 DESULTORY SKETCHES IN NATURAL HISTORY. 



We find this remarkably illustrated in the small group, of the 

 value of a sub-family, which we have selected as affording an in- 

 teresting subject with which to commence the present series of 

 Sketches on the Natural History of the Vertehrata, wherein we 

 propose to investigate the characters on which various groups of 

 animals are founded, and more particularly those of the genera and 

 higher divisions which appear to stand forth in an isolated manner 

 from the rest, in consequence of the distinctive features of confor- 

 mation characteristic of the immediately superior group, to which 

 they naturally appertain, merging, in some instances, almost to 

 obliteration, in extensive adaptive modifications having reference to 

 some particular habit. 



In order that we should be here duly understood, it is, perhaps, 

 necessary to premise, that, although the entire series of Vertebrata, 

 and, to a certain extent, the whole animal kingdom, may be ulti- 

 mately referred to one general type or single universal plan of or- 

 ganization, more or less developed, and variously modified in dif- 

 ferent classes of beings, yet it must not be supposed, with some 

 authors even of celebrity, but principally those who neglect to study 

 the internal conformation of beings, that the systematic arrange- 

 ment of animals is founded on arbitrary lines of demarcation, like 

 the meridians of longitude and parallels of latitude traced on a globe 

 or map ; that, in truth, there are no real divisions, except those of 

 species ; and that, consequently, the efforts of systematists must 

 necessarily be frivolous and futile, when they endeavour to define 

 rigorously the boundaries of their several groups and successive di- 

 visions, which are supposed to pass insensibly into each other by a 

 concatenation of intermediate forms, an unbroken series of gradations. 



That such is most assuredly not the case, a moment's reflection 

 on the four comprehensive grand divisions established by Cuvier, of 

 Vertehratttj Mollusca, Articulata, and Radiata, might suffice to in- 

 timate; inasmuch as these could never have been so definitely 

 determined, the multitude of intervening links which such an hypo- 

 thesis necessarily implies being utterly at variance with the suppo- 

 sition. Not but that certain organisms have been adduced as con- 

 stituting bonds of connection between these primary emhranche- 

 merits, but only on a superficial apprehension of their intrinsic 

 characters : for instance, the approximate obliteration of the verte- 

 brated column in the lowest cyclostomatous fishes, has induced some 

 authors to regard these as intermediate to the Vertebrata and MoL 

 lusca ; while an analogous link, or tendency on the part of a 

 molluscous animal to assume the vertebrated sub-type of organiza- 



