340 ON A HERMAPHRODITE AND 



AnnSlides or Scoleides at all, but that we must arrange under the 

 former head all those worms which resemble the errant and tubicolar 

 sea worms more than anything else, while those which resemble the 

 land and fresh water worms must fall under the latter category. If, 

 from the great division of the Annulosa, we take away those animals 

 which are characterized by the possession of one or more of the follow- 

 ing characters — i. Articulated appendages. 2. Such appendages 

 modified into jaws around the mouth. 3. A true heart in communica- 

 tion with the perivisceral cavity : that is, the Insecta, Myriapoda, 

 Arachnida, and Crustacea — we have left a large division of the animal 

 kingdom, to which the old term of Vermes might well be appropriated^ 

 had it not been already used in so many significations. For this 

 division, whose members are united by a marked community of 

 structure and development, and which includes th& Annelida of Cuvier 

 and a large section of his Radiata, viz., the Eniozoa, the Rotifera, and 

 the Echinoderinata, I have elsewhere proposed the name oi Annuloida,. 

 a term parallel to that very useful one of Molluscoida {Molluscoides),, 

 invented by Milne-Edwards for the Polyzoa and Ascidians} 



If it be remembered that it is only within the last few years that the 

 structure and development of these Annuloida — which present extra- 

 ordinary difficulties to the investigator — have been made the subjects, 

 of thorough and complete examination, it will not be a matter of 

 surprise that, at present, the subordinate division of the group must be 

 effected more by reference to types than by exact definition. Of course 

 this is still more the case with the smaller sub-divisions ; and until 

 much more light has been thrown on these most interesting but 

 most perplexing creatures, I think it would be well to understand 

 the existing classes and orders to be purely conventional and artificiaL 

 For my own part, I doubt greatly whether any well-marked natural 

 demarcation can, at present, be drawn between the Annelida (M. E.) 

 and the Scoleidce, or between these and the Entozoa , or, again,. 

 between the latter, the Turbellaria, and the Rotifera ; or, once more, 

 between the Annelida and th.e Echinoderntata ; though I have little 

 doubt that the progress of inquiry will tend here, as elsewhere, to 

 eliminate osculant forms, and to substitute definitions for types. 



Not only does it appear to me that, under these circumstances, it 



^ In writing this passage it escaped my memory that the very same division had been long 

 ago proposed by Milne-Edwards himself : 



" Je crois qui'l faudrait diviser cet embranchement (Les Articules) en deux groupes 

 principaux, I'un les articules a pieds articules, et I'autre les annelides, les Helminthes, 

 les Rotateurs, &c., serie a laquelle on pourrait donner le noni vulgaire des Vers." Sur K 

 Circulation dans les Annelides. Ann. des Sc. Nat., 1838, p. 194. 



