2470 The Sea-side Book. 



" All these animals inhabit sandy or muddy places. Their dead sheik are among 

 the commonest which we meet with on almost every strand ; and they may be found 

 in a living state, near low-water mark, buried in holes, which reveal themselves by 

 slight depressions, from which little jets of sand and water may, every now and then, 

 be seen to issue. For such a life as this their organization peculiarly fits them. Were 

 their mantle open on all sides, like that of the scallop, their branchiae would soon be- 

 come choked with the sand or mud, which would have free entrance with the water 

 received into the shell, and thus the animal would quickly be suffocated. But the 

 tubular opening through which the currents of water enter effectually protects the de- 

 licate breathing-apparatus. Their strong muscular foot, too, affords an instrument 

 with which they can with great rapidity dig into the sand, and thus escape pursuit. 

 So rapidly is this mining operation performed that it requires some dexterity and 

 quickness to surprise even a cockle in its hole, before it has burrowed beyond our 

 reach. But it is not as a digging tool only that the foot is employed ; it is used in 

 actual locomotion on the surface, to enable the animal either to advance with a crawl- 

 ing movement, or to make jumps along the sand. The common cockle is not the 

 least nimble of these jumpers. It protrudes its foot to the utmost length, bending it 

 and fixing it strongly against the surface on which it stands, and then, by a sudden 

 muscular spring, the animal throws itself into the air, and, by repeating the process 

 again and again, it hops along at a rapid pace. In the cockle, which lives at no 

 great depth in the sand, the cohesion of the two membranes of the mantle is not com- 

 plete, and the tubes or siphons are very short. In other genera, as the razor-shells, 

 which burrow to a greater depth, the lateral cohesion is much more perfect. The body 

 of the animal is enclosed in a sort of sac, while the tubes, through which currents of 

 water enter to the branchiae, are much protruded. The animal can thus lie deeply 

 ensconced in the sand or mud, and keep the mouths of the tubes nearly on a level 

 with the surface of the sand, in direct communication with the water. 



" The mode in which all the animals of this class feed is not the least curious part 

 of their history. They subsist, for the most part, like vegetables, without the trouble 

 of seeking for prey. It is brought to the door of their shells, and they have but to 

 4 gape and swallow it.' The water which enters at the openings in the mantle brings 

 in with it nourishing particles of one kind or other, minute animals, &c. These, 

 floating about in the shell, come under the influence of millions of minute cilia or 

 vibratory hairs, which clothe every part of the branchial fringe, and which, by their 

 constant motion, form a current strong enough to drive forward to the mouth whatever 

 is floating in the water. The food is thus presented to the lips, which have only to 

 decide whether to receive it or let it pass into the influence of the retreating current, 

 which will carry it out of the shell. To so low a type is animal will reduced in these 

 passionless creatures, which, nevertheless, exhibit the most wonderful perfection in 

 the construction of their minutest organs, and the most beautiful adaptations of means 

 to ends. The beauty of the shells of many of them is apparent to all — the graceful 

 forms of many species of Venus and Chione, — the rich colouring of the Pectens, the 

 Spondyli and Tellinae — but all these beauties are less impressive to the mind than the 

 exquisite structure of the mantle by which these shells are secreted, and the admirable 

 order with which the very particles of the shells are arranged : an order so exact, that 

 the species to which a minute fragment of a shell belongs may often be determined, or 

 approximated to, by making a microscopic examination of thinly-cut slices. Thus, 

 an examination of shelly particles, no bigger than grains of sand, may reveal to the 



