The same observations apply to the vessel A; in this case the liquid that remained in the flask was covered with a gelatinous and frothy mycelium. On October 20th, 1872, after a lapse of three months and a half, we poured the liquid from the test-flask attached to flask C back again to that flask. The test-flask connected with flask B we left untouched alongside the other flasks to serve as a means of comparison. On October 21st, 22nd, 23rd, we observed nothing; on succeeding days, however, some patches of bubbles appeared on the surface of the liquid in flask C, and clusters of mycelium buoyed up by the bubbles of gas which they imprisoned. Life had resumed its course, and with life fermentation had recommenced. What had been the cause of this change in the condition of the liquid, after an absolute quiescence of three months? There can be but one answer to this question: for in the other vessels there was no corresponding movement, or sign of life to be detected. In this vessel, however, an aeration of the plant had evidently taken place, consequent on the decantation and contact with the atmosphere of the flask, which communicated with the exterior air through the curved tube. This aeration had been absent or ineffective before decantation, in consequence of the great depth of liquid in the test-flask, the surface of which, too, was covered by a mass of mycelium filaments, itself effectually opposing any aeration of the liquid. Moreover, the surface of the liquid in the narrow neck of the test-flask had necessarily been covered by a layer of carbonic acid gas. We may investigate more thoroughly the influence of aeration, and its relation to the resumption of life in the mycelium of _mucor_, by restoring the liquid to its previous condition of depth and so cutting off again contact with the air. For this purpose, on October 31st we decanted once more the liquid and its deposit from the flask into the test-glass. The same evening a slight but continuous fermentation, with formation of froth, appeared on the surface of the liquid in the neck of the test-glass. Fermentation although never vigorous, continued the following days, and until December 20th. Between December 20th and 23rd, it ceased altogether to manifest itself by liberation of gas. As for the flask B, during all this time it had remained quite inactive and in the same state in which it had existed since June 29th, although the oven had on several days been heated to 28° C. (82° F.). On December 23rd, 1872, wishing to assure ourselves of the state of the plant in flask B, we subjected it to the same operation to which the flask C had been subjected on October 20th: that is to say, we poured the contents of the test-glass back into the connected flask, with the object of supplying the plant with oxygen. On December 24th, 25th, 26th, 27th, there was no apparent change.