404 ON THE ORDERS 



natural limits of the osculant classes, but even as to their 

 types and those points of the classes which they accu- 

 rately meet. I deem it preferable, however, to express 

 this uncertainty by notes of interrogation or asterisks, 

 rather than pretend to that acquaintance with the truth, 

 which can only be obtained by analysis. 



In conformity with the prevailing disposition of natu- 

 ralists to generalize anatomical facts, and their anxiety to 

 reach the simplex diintaxdt et unum, it may now be ex- 

 pected that I should endeavour to give the reader an abs- 

 tract idea of an Annulose structure, that I should enter, in 

 short, upon one of the most difficult and obscure provinces 

 of Natural History. Unfortunately, however, little more 

 progress has been made in this direction of the science 

 than such as may be summed up in the recital of a few vague 

 conjectures, and one or two probable hypotheses, which 

 their authors are still only preparing the proper means to 

 substantiate. It may, therefore, be somewhat bold in me 

 to attempt criticism on a question beset with so many 

 difficulties ; but as this species of inquiry is, if not the 

 first, at least one of the best steps towards a right under- 

 standing of those animal constructions which are framed 

 on a plan different from that of Man, a great object will 

 be attained if I do no more than explain in what these 

 difficulties consist. 



In all his demonstrations of a peculiarity in the forma- 

 tion of Unvertebrated animals, the naturalist is under the 

 necessity of referring constantly to the more generally un- 

 derstood structure of the Vertebrata ; not, however, that he 

 would reduce every living creature to the Vertebrated tyjx; 

 of form, or even insist upon anydirect affinity between plans 

 so fundamentally difierent, for this would be a great mistake ; 



