S40 ON THE CLASSES OF THE 



group coheres ; for if we consider it as formed of animals 

 creeping on a fleshy disc placed under the belly, there are 

 several of the Gasteropoda which do not possess this cha- 

 racter ; though on the whole perhaps this distinction is the 

 least liable to criticism, from its appearing to fail only at 

 those points which in the above series I have considered 

 as the extremities of the group. Cuvier has placed the 

 Cyc/o^rctAicAes near his Acephalous Molluscu, though on 

 what principle it is difficult to discover, unless it be on that 

 which is at least as yet doubtful, namely their self-fecun- 

 dation. Now this power, granting it to e^ist, when sup- 

 ported by other anatomical characters, would be most im- 

 portant for our purpose i but unsupported in a family like 

 the Gasteropoda, in which the method of reproduction va- 

 ries so constantlyj it is absolutely of no value whatever; 

 and when we see the genus Chiton placed close to the 

 Oyster on such reasons, we cannot help concluding that 

 among the MoUusca at least, the solitary consideration of 

 the method of reproduction will lead us to no satisfactory 

 results. This was too evident to escape the sagacity of 

 Lamarcky who has accordingly formed his family of Phil- 

 lidiens so as to include Cuvier's Cyclobranches and Infero- 

 branches. The Sctitibranches of Cuvier however have a 

 direct and obvious affinity with the Cyclobranches by 

 means of the genera Capulus and Crepidula, and again by 

 means of the Sigareta they lead us to the genus Buccinum 

 and others of Cuvier's Pectitiibranches. But this author 

 states that he is " assezporte a croire que les Scutibranches 

 sont des hermaphrodites qui peuvent sc suffire a euxmimes 

 comme les Acephales ;" and on this account, as well as be- 

 cause the heart is pierced by the rectum and receives the 

 blood by two aurides, he considers a certain affinity to 



