1899] MOULLINOUCLEAR CELLS 437 
ance, but in the dermatogen cells vacuoles may be detected in its 
interior, it is immediately surrounded by a more or less broad invest- 
ment of perfectly clear substance, the “ Hof,’ which is sharply 
marked off from the granular, peripheral nuclear substance. 
The first step in the division of such a nucleus is the division of 
the nucleolus. Immediately after division the two nucleoli lie in one 
“Hof.” In the next stage that can be found each nucleolus is 
surrounded by its own “Hof.” This clear belt grows more and more 
pronounced whilst the granular nuclear substance is gradually encroached 
upon and finally forms only a peripheral investment to the clear balls 
of substance which surround the nucleo. The thin layer of granular 
substance that lies between the two clear areas appears to disintegrate 
or at any rate to separate without any previous constriction, and the 
two spheres of clear substance, each containing a nucleolus, are 
separated from one another and form the daughter nuclei. The clear 
body-substance of these daughter nuclei becomes later more granular, 
and the nuclei may move some distance apart. 
Observations show that it is not merely a question of the dis- 
integration of the granular layer between the clear areas, but that there 
is an actual strain pulling the nuclei in two. 
It should here be mentioned that every nucleus which is provided 
with several nucleoli must not necessarily be regarded as indicating 
a stage of nuclear fragmentation, although by far the majority of 
resting nuclei have, in Zea, only a single nucleolus each. 
When older leaf-sheaths of Zea Mays are examined, nuclear frag- 
mentations are seen, which differ considerably from those which" have 
been mentioned above, and conform much more nearly to the stages 
which have been described in other plants by previous observers. 
The first and most obvious difference between direct nuclear 
division in the younger and older cells of Zea is that whilst the former 
takes place without the appearance of constrictions and changes of 
form in the nucleus, the latter is conspicuously marked by the grotesque 
intermediate shapes which that body assumes. 
The entire absence of constricting nuclei in the young leaf-bases, 
which are obviously developing multinuclear cells, is the most 
characteristic and at first the most puzzling feature about them. 
Another point in which the older nuclei differ from the younger is that 
in the former no constant relation between fragmentation and a pre- 
ceding nucleolar division can be made out. Sometimes two or more 
nucleoli appear here also, and one goes to each fragmentation product, 
but just as often one nucleolus alone is present throughout the 
process. 
These differences, which at a first glance are so striking, are 
possibly associated with the alteration in constitution which the 
nucleus suffers with advancing age. The young nucleus is large, and 
has every appearance of being rich in water; the nucleus of the older 
