FIRST FORMS OF LIFE. 31 



allied to the sea-pens of modern seas, a family usually inha- 

 biting mud and slimy sediment in deep water. We come to 

 creatures comparatively well organized, and yet still within 

 the lowest division of the Animal Kingdom, when we speak 

 of Crinoidea, which might be described as a lowly kind of 

 star-fish, fixed on the top of a flexible stalk arising from the 

 sea-bottom. Numberless calcareous plates enter into the 

 composition of the stalk, body, and multitudinous tentacula or 

 arms of the crinoid, forming altogether a wonderful example 

 of the elaborateness of pattern on which nature sometimes 

 works ; and yet it is a very humble animal, only, indeed, a 

 stomach of one aperture, with arms wherewith to supply 

 itself with food. The echinodermata, however, to which 

 order it belongs, are the destructives of their grade ; and 

 thus soon, it therefore appears, were animals set up as a police 

 over the rest, to effect the great providential object of con- 

 trolling the numbers of living beings. 



We have spoken of the Animal Kingdom and one of its divi- 

 sions. It may be well here to state that these divisions have 

 a reference to the grade and general character of the animals. 

 An animal is said to be low, when its organization is of a 

 simple kind, subservient to a comparatively narrow range of 

 functions, and suited to a comparatively narrow field of exist- 

 ence, if, like the polypes, for instance, and crinoids, it be 

 fixed in situation, and consist mainly of an alimentary recep- 

 tacle, with means of filling that with food. Elevation is 

 marked in the scale, by an animal ceasing to be compound 

 (which is the case of the coralline polypes), assuming a 

 power of locomotion, having sex assigned to separate indivi- 

 duals, exchanging a multiplicity of parts serving one end (as 

 the many pairs of feet in the centipede) for a smaller number ; 

 attaining, in short, at once a more complex and more concen- 

 trated organization. On such grounds, the animal kingdom 

 may be primarily divided into Vertelrated and Invertelrated ; 

 animals with a back-bone and the superior nervous system 

 which that structure implies, and animals devoid of that 

 structure and possessing a humbler nervous system. In the 

 latter are placed, first, the rayed animals {Radiata) ; then, on 



