236 FUNCTIONS AND INSTINCTS. 



a medullary ganglionic chord, but only dispersed 

 ganglions which send forth the requisite 

 nerves ; both have a double or bilobed mantle, 

 gills on each side, and a heart and circulation. 

 The Cirripedes indeed seem to be of a higher 

 grade, at least their nervous system is more 

 perfect since they have a longitudinal spinal 

 marrow with ganglions, a mouth furnished with 

 toothed jaws disposed by pairs, and jointed 

 tendril-like organs about the mouth and ap- 

 proaches near to that of the Annulose animals, 1 

 the Condylopes of Latreille. These, therefore, 

 may be considered as properly entitled to the 

 denomination of a Class ; but should not be 

 placed at a distance from the Crustaceans, to 

 which Lamarck, with reason, thinks they make 

 a near approach, as they are by Cuvier and 

 Cams. In fact, they seem to have little to do 

 with the bivalve Molluscans, except in being 

 defended by more than one shell, and having 

 no head. 



I shall now mention the most prominent cha- 

 racters of those shell-fish, that I regard as strictly 

 entitled to the denomination of Molluscans. 



ANIMAL soft, without articulations. Mantle 

 bilobed, enveloping more or less the animal. 

 Gills varying. A heart and circulation. No me- 

 dullary chord with ganglions, but a few scattered 

 ganglions from which issue nerves to various 



1 Annulosu. 



