ARRANGEMENT OP THE ANNELIDES. 19 



communicate with branchial pouches. The mouth 

 is still surrounded by a lip proper for suction, and 

 contains three maxillae, one answering to the soli- 

 tary upper tooth of the Gastrobranchus, and the other 

 to the lateral teeth of its tongue. These maxillae 

 are minute, compressed, and serrated with very small 

 teeth. The affinity of the leech to the cyclostomous 

 fishes seems to have been first perceived by Linneeus, 

 as appears by the place which he gave to his genus 

 Myxine. When, moreover, we find their habits to be 

 so similar, it may be said that nothing more is wanted 

 to complete the resemblance, than that the wrinkled 

 membranaceous skeleton of Ammocostus should, in the 

 leech, be supposed to form the envelope of the whole 

 animal." Our author, nevertheless, remarks, that " a 

 great alteration, however, has now taken place in the 

 internal structure, notwithstanding the above very evi- 

 dent affinities." That the Annelides, on the other 

 hand, approach to true insects, through the medium 

 of the JVereidte, or sea- worms, is highly probable. 

 These latter are more complicated in their structure 

 than any others, from possessing a head, antennae, and 

 blackish points resembling eyes : these eyes, however,' 

 are so imperfect, that Latreille compares them to the 

 rudimentary ocelli visible in caterpillars and other in- 

 sect larvae. From the Nereida, moreover, agreeing in 

 certain particulars, relating to their organs of reproduc- 

 tion, with the Myriapoda, Mr. MacLeay considers that 

 there is an affinity between them. He observes, " If to 

 these considerations be added their vermicular motion, 

 the form and disposition of their feet, the two last of 

 which are sometimes, as in Nereis margaritacea, trans- 

 formed into filiform appendages, exactly similar to those 

 which terminate the body of several Myriapoda, we can 

 have no doubt," concludes our author, " of our having 

 at length reached truly the annulose animals, which are 

 white-blooded, and are externally articulated." * All 



* HoraeEnt. p.282. 

 C 2 



