Thus the work on the joint action of the amylases under the brewery mashing conditions has given sane information about the general behaviour of the amylases in addition to being of help for an understanding of the amylolyatic action in the mash tun. It is however, fully realised that simple laboratory experiments of the type described cannot fully simulate the conditions of brewery mash and more work must be carried out before a complete picture of the amylase action in the mash tun can be obtained. The substrate used has been soluble starch for the bulk of the experiments and in *1 per cent, concentration 5 as against this in the mash there is malt starch in about 20 per cent. concentration; both concentration and type are likely to affect the various starch conversions and their influences are worth investigating. In the present work, study of the influence of concomitants on the reactivity of amylases has not been undertaken; though, certain effects of these are clearly indicated at various stages of the work. There are a number of these present in the malt and therefore starch conversion in the mash tun is amylolysis in presence of innumerable other reactions, which exert some influence. Study of the effects of these concomitants is complicated but worth proceeding with. Again, the expression 'fermentable sugar' is by no means precise; we do not know what are the fermentable sugars present and in what proportions they are present. Apart frcm glucose and maltose it is claimed that various fermentable trisaccharides are present. Owing to the lack of suitable methods the estimation of these sugar's with reasonable accuracy has not so far been possible, but it is to be hoped that chromatographic analysis, particularly partition chromatography which is rapidly gaining importance in the estimation of sugars, even in minute quantities (Flood, Hirst and Jones, 1948; Partridge, 1948) will be of great help in the estimation of the individual fermentable sugars. This would not only help in an understanding of amylase action but also in clearing up some of the doubts about starch structure. However, taking these and other similar criticisms into account, it is still hoped that the claim can be made that suitable lines of working have been developed and useful results obtained as a preliminary to the more detailed study of the mash tun amylolysis, which must ultimately be undertaken.