It has been a matter of dispute with naturalists whether the testaceous mollusks have shells at all before they issue from the egg, and the main evidence favours the opinion that, generally speaking, they do possess what may be considered as a kind of pattern or model of the habitation which they are to build. This appears to be of a pale horn-colour, and destitute of any markings; but as soon as the animal enters upon an independent state of existence, it begins to assume its distinctive shape and colour, gradually increasing with the growth of its living tenant, and becoming more and more decidedly marked, until it attains its full perfection of testacean development. Thus the age of some shell-fish can be at once determined by the peculiar conformation and markings of the shell. The relative portions of animal and earthy, or rather chalky matter, which compose these shells, varies considerably in different kinds; in those called Crystalline or Porcellaneous, the animal deposit is much less than in the granular or concretionary shells, where it not only constitutes a large part of the whole substance, but is more dense, that is thick, and also has the appearance of being membraneous, or organized matter. We can perhaps best explain this by saying that whereas the different chalky layers of the crystalline shell seem merely glued together by the intervening animal fluid; those of the granular shell, as the oyster, appear to be connected by interlacing membranes. But all this my readers will learn more about from more advanced and scientific works if they proceed, as I trust they will do, in the study of CONCHOLOGY, a science which has in a greater or less degree attracted the attention of curious and contemplative minds in all ages, and the study of which it has been well said is peculiarly adapted to recreate the senses, and insensibly to lead us to the contemplation of the glory of God in creation. BEAUTY AND VALUE OF SHELLS. In shells, as in all the works of the Almighty Creator, we may observe an infinite variety of form, and if they do not all strike us as alike graceful, yet in each, however plain and simple, there is some peculiar beauty, whether it be the mere hollow cup, or the simple tube, the smooth or twisted cone, the slender spire, the convoluted oval, or half circle, ribbed or spiked, with a lip curving out like the leaf of a water lily, or a narrow rim, like that of a golden chalice; they are indeed elegant, each perfect of its kind, and bearing the impress of a constructive skill far above that of man, who copies from them some of the most graceful and elegant designs wherewith to ornament his buildings, and shapes in which to fashion his articles of luxury or utility.