To these must be added the ordinary ferment of wine, and that called _apiculatus_, although, indeed, these last are of little practical importance, since, in general, they soon become lost amongst others of greater vitality, in the spontaneous fermentation of fruits. These are not the only alcoholic ferments; a study of the germ-cells diffused over the surface of fruits, grains, and stalks of all vegetables in different countries, would doubtless lead to the discovery of many new ones. We are even inclined to believe that one ferment might give rise to a multitude of others. The investigations which we have undertaken in this direction are as yet not far advanced; we may, however, be allowed merely to state the principle which governs them. A ferment is a combination of cells, the individuals of which must differ more or less from each other. Each of these cells has certain generic and specific peculiarities which it shares with the neighbouring cells; but over and above this, certain peculiar characteristics which distinguish it, and which it is capable of transmitting to succeeding generations. If, therefore, we could manage with some species of ferment to isolate the different cells that compose it, and could cultivate each of these separately, we should obtain as many specimens of ferments, which would, probably, be distinct from one another, inasmuch as each of them would inherit the individual peculiarities of the cell from which it originated. Our endeavours are directed to realizing this result practically, by first thoroughly drying a ferment and reducing it to fine powder. We have seen (Chap. III. § 6) that this mode of experiment is practicable, that in a powder composed of yeast and plaster the ferment preserves its faculty of reproduction for a very long time. If we now drop a small quantity of this powder from a sufficient height, and then, at a certain distance below the cloud of dust so formed, open several flasks previously deprived of air and containing a fermentable liquid that has been boiled, immediately closing them all up again, under such circumstances it is conceivable that some of the cells of yeast diffused in the cloud of dust, and separated widely in the act of falling, will enter some of our flasks singly, and there develop an appreciable weight of ferment, all the cells of which will have sprung from the same mother-cell. We have proved that flasks may be easily impregnated under these conditions, and our preliminary observations, although incomplete, seem to favour the idea that numerous varieties of ferment are to be obtained by these means.