OF THE ANNULOSA. 407 



locomotion in the Annulosa with each other, such enor- 

 mous discrepancies are to be remarked, that we are, on a 

 slight view of the subject, ahmost tempted to beheve that 

 the torch of analogy throws little light on the anatomy of 

 such organs out of the circle of Vertebrata. 



Not content with the group of Annulosa being held to- 

 gether by their nervous system and external articulation, 

 characters which they possess in common with the Cir- 

 ripeda and Annelides, M. Savigny was the first who un- 

 dertook to reduce this uniformity to more definite princi- 

 ples, and thus to afford us a more distinct and precise per- 

 ception of the Annulose model. For this purpose he 

 directed his attention to the construction of the mouth in 

 Hexapod insects undergoing metamorphosis, and appears 

 to have succeeded in reducing this astonishing variety of 

 mechanism to one general type. It was then reasonably 

 expected that the same theory, carried a step further on to 

 the Crustacea and Arachnida, would produce similar ef- 

 fects, and that the entomologist would be able to under- 

 stand the general plan upon which those organs are formed, 

 which principally contribute to the life of an Annulose 

 animal. So far, however, is this just expectation from 

 having been realized, that the chief information to be 

 drawn from the second Memoire of M. Savigny relates 

 to the individual construction of those species of jdpiro- 

 poda which he has examined, and indeed does little more 

 than explain the gradual adaptation of their feet to pur- 

 poses of manducation ; — a fact certainly of the most inter- 

 esting kind, but which can only by analogy be directly 

 connected with the object he had in view. I have no 

 hesitation in saying, for my own part, that, notwithstand- 

 ing M. Savigny 's industry and wonderful talent for gene- 

 ralizing facts collected by the most sound experiments, I 



