342 Dr. W. C. M'Intosh on the abdomen ; the importance, therefore, of ascertaining by close inspection whether the line and the viscid fluid in which it is enveloped proceed from the same spinning-tube or not will be immediately apparent. It is evident, from the materials of which they are composed possessing such widely different pro-perties, that they cannot be produced by the same organ of secretion. There is a difficulty also in comprehending how a cylindrical body of viscid fluid can be resolved by molecular atti-action into a series of large and small globules disposed on the line alternately at minute and most regular distances from one another. Had Mr. Beck been spared to continue his researches, he might perhaps have been enabled, by his well-known skill as a microscopist and by the advantage he possessed in having superior optical instruments at his command, to throw some light on the obscure phenomena here submitted to the consi-deration of arachnologists, which remain as problems yet waiting a solution. XLVIII. — On the Invertebrate Marine Fauna and Fishes of St. Andreios. By W. C. M'Intosh. [Continued from p. 815. J Section II. MOLLUSC A (proper). The Mollusca are chiefly procured by dredging, examina-tion between tide-marks, or the deep-sea lines of the fisher-men, though certain storms sometimes strew the sands with many species in great profusion. Not a few of the rarer forms are found in the stomachs of fishes, such as the cod, haddock, and flounder. The remarks on the class may be arranged in three divisions, founded on the economical value, peculiar habits, and rarity. By far the most important species in the first group is the common mussel {My tilus ednlis) , which, occurs in vast numbers in the form of mussel-" beds " on muddy flats, chiefly situated on the right bank of the estuary of the river Eden. Attached to stones, sticks, and to each other, these shell-fish luxuriate in abundance of Diatomaceae, Infusoria, and other minute forms of animal and vegetable life. From their special value as bait the city derives a considerable annual revenue ; and if the wise protection only lately enforced were supplemented by
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