5 6 7 
Constituents of the Cell. 
and as supporting, in a measure, Boveri’s view that the so- 
called nuclear sap is not a specific or peculiar substance. 
Evidence from the botanical side is much to be desired, as to 
whether, as this author believes, the nuclear membrane is 
merely a bounding layer of the cytoplasm enclosing the 
nuclear cavity. 
Zimmermann (’93) observed in the sexual cells of Lilium 
Martagon that, as he believes, only at a certain early stage of 
their division the nucleolus becomes flattened against the 
nuclear membrane, constituting what he has called its sickle- 
stage , which was earlier referred to by Strasburger under the 
names ‘ Sekretkorperchen ’ and ‘ Paranucleolus.’ He has 
attempted to connect this peculiar phenomenon with the 
reduction of the chromosomes, holding that it occurs only in 
the stage immediately preceding that process. During studies 
of various tissues, my attention was occasionally attracted by 
crescent-shaped accumulations against the nuclear membranes, 
often so great as to distort the nucleus. These are commonly 
present, if at all, in all the nuclei of a section, even when it 
includes both vegetative and reproductive tissues, and in 
resting nuclei as well as in those beginning to divide. The 
presence of these accumulations always on the side of the 
nucleus turned away from the nearest surface of the organ 
(cf. Figs. 3 and 4 of my previous paper) showed clearly that 
they are caused by the uneven penetration of the fixing fluid, 
which carries with it, until stopped by the nuclear membrane, 
certain deeply staining constituents of the nucleus. The 
reactions of the accumulations with stains made it very 
doubtful if they contain any nucleolar substance, but rather 
chromatin, a conclusion with which Strasburger has lately 
expressed (’95) his agreement. Since no similar bodies with 
the reactions of nucleoli were found in the tissues examined, 
it was believed that these represented the £ sickle-stage ' of 
Zimmermann, which was therefore explained as due to im- 
perfect fixation of the material. This identification was 
probably hasty, in view of the fact that Zimmermann figures 
his bodies as staining precisely like nucleoli. And he has 
