ZOOPHAGOUS GASTEROPODS. 307 



ship of the Gasteropods in question. Fixing the shell of tlieir 

 prey by the disc of the foot^ they apply against the point 

 where they mean to penetrate, the apex of the proboscis; 

 and now, by a constant rubbing or grating of their filiform, 

 rough, spinous tongue, assisted, as some affirm, by the 

 softening action of some solvent, they succeed, after much 

 pains, in perforating through the valve.* Reaumur, who 

 investigated the subject with great care, was the first to 

 suggest that the process was not entirely mechanical. He 

 found, in the first place, that the hole was not invariably 

 of the same form, as it should have been had it been worked 

 out by an instrument which does not vary in its make, but 

 some of the holes were round and some oval ; Sndly, the 

 bottom of the hole is as wide as its entrance, a kind of 

 bore which a pointed instrument could not effect; and 

 Srdly, he detected in the bottom of some unfinished holes 

 a stronger water, which he concluded to be of a solvent 

 quality. This solvent, Cuvier thinks, is furnished by the 

 anterior salivary glands, which open forwards into the pro- 

 boscis ;-j~ and this opinion is more probable than that of 

 Dr. Bancroft, who conjectures that it may be the same as 

 the purple secretion. This fluid, as I formerly told you, 

 when exposed to the light gives out an odour nearly resem- 

 bling that of garlic. " This odour, to my senses," says Dr. 

 Bancroft, " unequivocally indicates the presence of phos- 

 phorus, which is contained in all animal substances ; and, 

 when subjected to the action of the sun's rays, readily be- 

 comes volatile in part by combining with a portion of oxygen ; 

 and this volatile part or compound (which, as Davy observes, 

 should, according to the principles of the French nomencla- 

 ture, be called phosphorous acid) emits an offensive alliaceous 

 smell, very much like that of the colouring matter of the 

 Buccinum, when it becomes purple. The last, or that part 

 of it which gives the smell of garlic, readily mixes with 

 water, and strongly impregnates it with this odour, as- I 

 have found by many experiments ; and in this respect it 

 also agrees exactly with the volatile compound which gives 

 the alliaceous odour from phosphorus." J 



* " The purple hath a tongue of a finger long, pointed in the end so 

 sharpe, and hard withall, that it is able to bore an hole and pierce into other 

 shell-fishes, and thereby shee feeds and gets her living." HOLLAND'S Plin. 

 i. 258. The ancients were better informed on this subject than some 

 modern writers, who have attributed these operations to the Trochus. See 

 Smellie's Phil, of Nat. Hist. i. 396. 



t Mem. xv. 9. 



t On Colours, i. 155. 



x 2 



