1284 
function ; that it can likewise lead to the factor analysis of a mor- 
phological character I will now endeavour to show with regard 
to the cell-wall. 
The formation of the cell-wall is commonly considered as a function 
of the. parietal protoplasm and must necessarily repose on the action 
of factors or heredity units. For some microbes this process is clearly 
caused by one or more enzymes and this is distinetly the case when 
the wall substance consists of levulan. This matter results from cane- 
sugar (and slower and less profusely from raffinose), but from no 
other substances. It forms the cell-wall of many species of sporulating 
bacteria, such as B. megathertum and also the common hay bacte- 
rium 5. mesentericus, but only if fed with cane-sugar. The levulan 
arises in two ways: it either remains in contact and entirely united 
with the bacterial body as a slimy cell-wall, in which case on cane- 
_ sugar-agar plates strongly swelling colonies develop, or the levulan 
is deposited outside the bacterial body at some distance from the colony. 
If the latter takes place the remarkable reaction occurs which I 
have called the “emulsion reaction’) Its explanation was given by 
the discovery of a specific exoenzyme, viscosaccharase, which acts 
‘on cane-sugar and converts it into levulan slime, which is in- 
capable of diffusion but attracts water, so that droplets are formed 
causing a strong swelling of the agar. This enzyme, acting synthetic- 
ally and evidently polymerising the cane-sugar, might as well be 
called saccharo-levulanase and is obviously one factor of the factor- 
complex that governs the cell-wall formation. That it is not the only 
one follows from the fact that some levulan bacteria, for instance 
the hay bacterium itself, when fed with other sugars, produce another 
not slimy wall-substance, probably cellulose, which likewise derives 
from cane-sugar beside levulan, but only in slight quantity. If the 
production of cellulose is brought about by one or more factors 
is not yet known. As to the viscosaccharase, however, there is not 
the least doubt but that it consists of one single enzyme or factor. 
Hence it may be concluded that it is quite well possible to become 
acquainted with the separate factors of a process at first sight so 
complicated as the formation of the cell-wall, and it may safely be 
predicted that further experiments will show whether the cellulose 
production also depends on one single or on more than one enzyme. 
On the other hand, at the factor analysis by crossing experiments 
with higher plants and animals, without the guidance of the enzyme 
conception, we are continually in doubt whether a factor, thought to 
') These proceedings 9 February and 2 Mei 1910. Folia microbiologica Bd. 1 
Pag. 382, 1912. 
