316 Bibliographical Notices. duce the slightest characteristic reaction in these. But tracing these enlarged cells in their course towards the point of the leaf, we find that, first, a very considerable spiral or annular thickening band is developed from their ovules ; and secondly, that these walls become perforated in particular localities, showing clearly that the cellulose wall is in itself abundantly competent to perform the vital actions of assimilation and absorption, or rather resolution, without the assist-ance of the primordial utricle. Nor let it be said, that here the thickenings and resolutions are determined by the primordial utricles of adjacent cells, for the Sphag-num leaf, as is well known, consists of only a single layer of cells joined side by side, and the thickening takes place as much on the upper and lower surfaces as on the sides of the spiral cells, while the perforations are formed exclusively upon the upper and lower sur-faces. Surely here nature furnishes us with a crucial instance of the independent vitality and powers of action of the cellulose cell-wall, whence important conclusions may be drawn for the whole vege-table kingdom. There is yet another error which we venture to submit pervades the whole of vegetable no less than animal physiology, — we refer to the notion that animals and plants are formed by the coalescence of their histological elements — the cells. It is said that plants are formed by means of cells which have "grown together^' (Von Mohl, p. 30), having "arisen separately as development teaches " (Schacht, p. 75) ; and this conception of the individuality of the separate plant-cells, though by giving distinctness to the ideas of investigators it has served a good purpose, seems to us to be at present essentially obstructive. If in fact we turn from this convenient mode of viewing the facts to the facts themselves as they really are, we find that the cells which compose any vegetable tissue never have been independent, and that therefore it is as absurd to talk of their coalescence, as to say that a man is formed by the coalescence of his head, trunk and limbs. Indeed, all the knowledge we have hitherto obtained of develop-ment, whether morphological or histological, uniformly bears testi-mony to the truth, that the great law established by Von Bar for the animal world holds good as universally in that of plants. They and all their organs, and all the histological elements of these organs, are produced, not by the coalescence of the heterogeneous, but by the dif-ferentiation of the homogeneous parts, and it would be more true to say that the plant is formed by the separation of cells than that it arises from their coalescence. This however is a most important subject, and one which we hope to follow out elsewhere. Handbuch der Conchyliologie und Malacozoologie. Von Dr. R. A. Philippi. Halle, 1853. 8vo, pp. 548. By the preface we are informed that this work was written on board the Hamburg brig Bonito, and dated while it was passing Cape Horn, the author having, by the late political disturbances in
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