KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 167 
Ch. van Bambeke (12), without further examination of the 
chemical composition of the envelope. 
In my opinion it is not finally proved what form is taken by 
the Balbiani-Pfitzner chromatin bodies. Pfitzner calls them 
“‘spherules ;” Strasburger describes them, both in his earlier 
as well as in his latest papers (191), as tub-shaped discs; as 
also does Carnoy for Arthropoda. 
The nucleoli present much difficulty in their interpretation. 
Itis generally known that they are roundish structures, which 
stand out distinctly from the rest of the constituents of the 
nucleus, and are stained deeply. It is, however, doubtful 
what relation they bear to the network. Some authors, for 
example Flemming and Pfitzner, regard the nucleoli as 
distinct from the network; they are to be considered as 
independent structures inside this; not in connection with 
the threads, but separate from them, although they appear 
arranged along them. Others, for instance E. Klein (1038), 
of London, regard the nucleoli as merely much-thickened 
knots of the network of threads, and as identical with 
these: I agree with him on account of their behaviour 
during karyokinesis. As a matter of fact such thick knots 
do occur in the chromatic network. These, according to 
Flemming (58), must be distinguished from true nucleoli. 
A glance at fig. 1 shows a well-defined and rounded nucleolus, 
in addition to the knots, or “net-knots” as they may be 
termed to distinguish them from the nucleoli. 
According to Pfitzner, true nucleoli never have any connec- 
tion with the chromatin coil, but le freely in its meshes. 
Apart from this, Flemming further finds differences in the index 
of refraction and in behaviour to stains. In Ceratium 
tripos, Biitschli found the nucleoli lying in the nucleus to be 
formed of a fine network. E. Zacharias (209) says that in 
plant-cells the nucleoli are deficient in the characteristic 
nuclear-constituent nuclein; but, on the contrary, consist of 
a network of plastin-substance, in the meshes of which 
are other albuminous substances. This would point to the 
independence of nucleoli. Carnoy (47) would distinguish 
