and on the removal of portions of their Shells. 245 



cussed — the power possessed by many of the Gasteropods of re- 

 ducing the thickness of the columella, and of removing spines 

 and other obstructions from it. 



Mr. Gray, who has entered on this matter at some length in 

 his paper (before quoted) in the ' Philosophical Transactions/ 

 states that " this absorption of the outer part of the last whorl 

 but one, and of the spines, is evidently effected by the edge of 

 the mantle." And there can be little doubt that the other in- 

 stances which that gentleman mentions of the " absorption " to 

 a greater or less extent of the septa is likewise effected by the 

 same organ. That this view is correct we have but to refer to 

 the mollusca of our own coast. The shell of Buccinum undatum 

 generally exhibits a groove on the columella extending the whole 

 length of the mouth ; and if a living specimen be examined, we 

 perceive that the edge of the mantle perfectly corresponds to this 

 groove. Fusus antiquus and Purpura lapillus also reduce the 

 thickness of the columella, and in both it is very easy for any 

 one to satisfy himself that the mantle is the instrument. In 

 Buccinum undatum the cutting of the columella is occasionally 

 very deep, especially when the part has been repaired and pro- 

 jecting a little ; in which case it is frequently under-cut, and 

 actually overhanging the mantle. 



It is difficult to say what is meant by " absorption '^ in these 

 cases : nothing like the absorption of hard, inorganic matters in 

 the higher animals can be supposed to take place here; for no 

 vascular connexion exists between the mantle and the columella. 

 Mr. Gray says, " Possessing this power of absorbing their own 

 shells and the shells of other mollusca and calcareous rocks, it is 

 remarkable that these animals do not exert it for the purpose of 

 removing extraneous obstacles which may oppose their progress 

 in the formation of their shells." Were this indeed the fact, it 

 would go far to support the opinion that vascular absorption, or 

 something like it, really takes place. I possess, through the 

 kindness of Mr. Richard Howse, two specimens which prove that 

 these animals, however, do remove extraneous bodies from the 

 columella. The one is a small individual of Buccinum undatum 

 with a Seipula attached to the spire, and passing over the pos- 

 terior part of the columella. This Serpula is completely cut 

 through undoubtedly by the mantle, and left overhanging it for 

 nearly a quarter of an inch. The other is a Fusus antiquum, 

 which has adhering to the columella two barnacles [Balanus com- 

 munis). These have the walls, that are next the mouth of the 

 shell to which they are attached, cut through ; proving beyond a 

 doubt that the mantle has the power of removing extraneous 

 matter that retards the growth of the animal. It is therefore 

 pretty evident that these removals do not take place by vascular 



