Some time ago, wishing to assure ourselves that the spores of _penicillium_ could not become transformed into ferment, we sowed some pure spores in small flasks, holding from 50 c.c. to 100 c.c. (from 2 to 4 fl. oz.), which contained very little air, and which were sealed hermetically after the sowing. Under these conditions, the germination and growth of the spores proceeded with great difficulty, and soon ceased through want of air. The total weight of the little plant was too small to be determined. In cases of this kind, if we distil the whole of the liquid we shall often see the alcohol appear in the second distillation, even though the weight of the plant may have been scarcely appreciable. If, on the other hand, side by side with experiments of this kind, we grow pure _penicillium_ in flasks containing air and having quantities of saccharine liquids equal to the quantities in the small flasks of which we have been speaking, the plant, in consequence of the large volume of air at its disposal, will develop vigorously, and in the course of even a few days will have become perceptibly heavier. In distilling the subjacent liquid, however, we shall generally find that it contains no alcohol at all, even though the weight of the plant be half a gramme, or more (6 or 7 grains). These results apply to all the fungoid growths that we have studied, but they vary considerably with the nature of the organisms. _Aspergillus glaucus_ is, in this respect, one of the most curious. On June 15th, 1873, we impregnated three flasks of wort, A, B, C, with pure spores of _aspergillus glaucus_. The development was rapid and the fructification abundant. On June 20th, we shook up the liquid and the supernatant fungoid growths in the three flasks; the flasks A and B were then treated as follows:— We distilled the Liquid in A to discover the presence of alcohol; but could find none. [Illustration: Fig. 19.] The flask B was connected with a test flask (Fig. 19), into which the liquid, together with its fungoid growth, was transferred from B. The next day, June 21st, the mycelium which was on the surface of the liquid, in the neck of the flask, was studded with bubbles of gas; these we dispersed by shaking. On June 22nd, many others had formed again, and a large flake of mycelium that had risen from the bottom of the test flask had been stopped at the bottom of the neck, quite distended by gas bubbles. We liberated the gas by shaking, but the bubbles formed again by the next day, and this effect continued for several days; nevertheless the liberation of gas was not continuous, as is the case in an ordinary fermentation. On July 20th we drew off the liquid and distilled it; it was still very sweet, but though it contained a sensible quantity of alcohol, the microscope failed to detect a single cell of ordinary alcoholic ferment.