OF THE ANNULOSA. 417 



tenvards become of a powerful size in the Muscida, besides 

 being assisted by a pair of tlioracic appendages termed 

 halleres, which finally themselves become wings in 

 other more perfect orders. 



A more troublesome office of the learned author of this 

 hypothesis will probably be to explain the conformity of 

 Myriapod animals to this Decapod construction, or at 

 least to show how they have gone beyond it, like those fishes 

 which apparently have overshot the tetrapod mark of the 

 Vertehrata. But as this leads us into speculations of a 

 very extensive nature, and not immediately connected with 

 our subject, I shall, for the present, merely state my in- 

 clination to adopt the following, opinion of M. Latreille, 

 viz. That every Annulose animal has a tendency to be De- 

 capod, or, more properly, to have jive pairs of thoracic ap. 

 pendages answering to the Jive thoracic segments; and thus, 

 although Nature may make particular exceptions to her 

 plan, it may eventually be necessary to describe that ima- 

 ginary being, the Annulose type of form. 



2 E 



