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LETTER XVIII. 



THE CARNIVOROUS MOLLUSCA. 



Although it may be true, as stated in the preceding- 

 letter, that the great proportion of the Conchifera subsist on 

 infusorial entities, or on food in a state of molecular division, 

 yet there can be no doubt that some of the larger and loco- 

 motive species seek a more substantial fare, and feed on 

 worms or other animal matter in a state of partial decay ; 

 which they seem to have the power of grasping by means of 

 their extensible labial appendages. Thus the large Cyprina 

 islandica and the Modiola vulgaris of our seas often swallow 

 the bait of the fisherman ; and in the stomach of an indivi- 

 dual of the former I once found the undigested remains of 

 a large green Nereis enveloped in a pulp too consistent 

 certainly to have been the sediment from water, however 

 loaded with molecules. 



In their manner of feeding, these Conchifera resemble the 

 pectinibranchial Gasteropods whose shells have a notch or 

 canal at the base of their apertures ; and it is important you 

 should remember that it is only, with a few exceptions, the 

 Gasteropods of this order (Pectinibranchia) so circumstanced 

 that are truly carnivorous. They embrace the cowries, the 

 cones, the volutes, the rock shells and the whelks, all of 

 which live on animal food ; and it seems to be indifferent to 

 them whether their prey is dead, or still fresh and alive ; 

 but, in the latter case, it is obvious, if you remember the 

 inactivity, and sluggishness, and total want of cunning of 

 these molluscs, that the prey they can master must be fet- 

 tered and stationary, or endowed with locomotive powers 

 and arms not superior to their own. It is not unlikely that 

 they may prefer a dead prey to a living one, for we know 

 that the whelks will take a bait readily ; in search of which 

 they frequently enter the baskets laid for crabs and lobsters, 

 which are always baited with garbage ; while in tropical 

 climes we are told that men fish for the olives with lines, to 

 which small nooses, each containing a piece of the arms of a 

 cuttlefish, are appended. 



You could never have anticipated that the Bivalved Mol- 

 lusca (Conchifera) would be found among the prey of these 



