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2 Wien, 1838, p. 14,) they in like manner consist of cells, the partition-walls of which become obliterated.

Animals, which present a much greater variety of external form than is found in the vegetable kingdom, exhibit also, and especially the higher classes in the perfectly-developed condition, a much more complex structure in their individual tissues. How broad is the distinction between a muscle and a nerve, between the latter and cellular tissue, (which agrees only in name with that of plants,) or elastic or horny tissue, and so on. When, however, we turn to the history of the development of these tissues, it appears, that all their manifold forms originate likewise only from cells, indeed from cells which are entirely analogous to those of vegetables, and which exhibit the most remarkable accordance with them in some of the vital phenomena which they manifest. The design of the present treatise is to prove this by a series of observations.

It is, however, necessary to give some account of the vital phenomena of vegetable cells. Each cell is, within certain limits, an Individual, an independent Whole. The vital phenomena of one are repeated, entirely or in part, in all the rest. These Individuals, however, are not ranged side by side as a mere Aggregate, but so operate together, in a manner unknown to us, as to produce an harmonious Whole. ‘The processes which go forward in the vegetable cells, may be reduced to the following heads: 1, the production of new cells; 2, the expansion of existing cells; 3, the transformation of the cell-contents, and the thickening of the cell-wall; 4, the secretion and absorption carried on by cells.

The excellent researches of Schleiden, which throw so much light upon this subject, form the principal basis for my more minute observations on these separate vital phenomena. (See his “ Beitrage zur Phytogenesis,” in Müller’s Archiv, 1838, p. 137, plates 3 and 4.)

First, of the production of new cells. According to Schleiden, in Phenogamous plants, this process always (except as regards the cells of the Cambium,) takes place within the already mature cells, and in a most remarkable manner from out of the well-known cell-nucleus. On account of the importance of the