By summarising the multirotatory sugars can be divided into 
three groups. 
1st group, of which we know only one representative viz. the 
d-glucose of which both modifications are retained. 
2nd group (d-galactose, d- and I-xylose, d-ribose) of which only 
one modification is retained. 
3d group (I-glucose, d-mannose, d- and |-arabinose) of which neither 
of the two modifications are retained. 
In the cases of the members of the second group viz. 
d-galactose and l-xylose which have been subjected 
to more detailed examination, the retention or non- 
retention is governed wholly by the position which 
the H and HO linked to the asymmetrie C-atom occupy 
relative to each other. 
It is worthy of comment still, in the first place, that the conjecture 
which we have offered here, and which ought to be controlled by a 
large number of experiments still, gives a physiological illustration 
of the existence of modifications, which formerly was found along 
chemical lines. 
In the second place it brings to light that if one desires to 
investigate stereoisomeric sugars with respect to lower organisms, 
as has already been done by several investigators, the fact has 
to be reckoned with, henceforth, that the sugar which is investi- 
gated is not a simple compound but a mixture, the two components 
of which need not behave similarly towards a microorganism. 
In these investigations Mr. R. Rorrink has lent his skilled 
assistance. 
Physiological Laboratory. 
Groningen, September 1919. 
