It has also been shown that the arguments adduced by Iwanoff in favour of the existence of his synthease are not valid [Harden and Young, 1910, 1]. The fermentation of dihydroxyacetone was moreover proved by Harden and Young [1912] to be effected by yeast-juice and maceration extract at a much slower rate than that of the sugars, in spite of the fact that the addition of dihydroxyacetone did not inhibit the sugar fermentation. The same thing has been shown for living yeast by Slator [1912] in agreement with the earlier results of Buchner [1910] and Buchner and Meisenheimer [1910]. The logical conclusion from Lebedeff's experiments would appear rather to be that dihydroxyacetone is slowly condensed to a hexose and that this is then fermented in the normal manner [Harden and Young, 1912; Buchner and Meisenheimer, 1912; Kostytscheff, 1912, 2]. Buchner and Meisenheimer, however, regard this as improbable on the ground that dihydroxyacetone, being symmetric in constitution, would yield an inactive hexose of which only at most 50 per cent. would be fermentable. Against this it may be urged, however, [p107] that enzymic condensation of dihydroxyacetone might very probably occur asymmetrically yielding an active and completely fermentable hexose. Buchner and Meisenheimer, however, still support the view that dihydroxyacetone forms an intermediate stage in the fermentation of glucose and adduce as confirmatory evidence of the probability of such a change the observation of Fernbach [1910] that this compound is produced from glucose by a bacillus, Tyrothrix tenuis, which effects the change both when living and after treatment with acetone. The balance of evidence, however, appears to be in favour of the opinion that dihydroxyacetone does not fulfil the conditions laid down by Slator (see p. 103) as essential for an intermediate product in the process of fermentation [see also Löb, 1910]. Lebedeff subsequently [1912, 4; Lebedeff and Griaznoff, 1912] extended his experiments to glyceraldehyde and modified his theory very considerably. Using maceration extract it was found in general agreement with the results of Buchner and Meisenheimer (p. 105) that 20 c.c. of juice were capable of producing about half the theoretical amount of carbon dioxide from 0·2 gram of glyceraldehyde, whereas 0·4 gram caused coagulation of the extract and a diminished evolution of carbon dioxide. The addition of phosphate diminished rather than increased the fermentation. Even in the most favourable concentration however (0·2 gram per 20 c.c.) the glyceraldehyde is fermented much more slowly than dihydroxyacetone or saccharose, as is shown by the following figures:--