258 Campbell. — On the development 
The Structure and Division of the Nuclei 
in the Embryo. 
Owing to their small size the nuclei of the embryo are not 
well adapted for the study of nuclear division. Except during 
the actual division the nuclear membrane is well defined. 
With safranin, or better with gentian-violet, the chromatin 
stains very intensely, the same treatment being used as 
recommended by Moll for the root-tips of Phanerogams 1 . In 
the actively growing embryo all stages of division may be 
found. As elsewhere, the amount of chromatin increases very 
perceptibly at the time of division, the resting nucleus showing 
but a small amount of chromatin, and the chromatin-masses 
being extremely small and scattered. A small nucleolus can 
generally be seen. A stage was observed (PL XIV, Fig. 28) which 
was not thoroughly understood. Apparently a single relatively 
large and intensely coloured body was present. This was so 
small in some cases as to be readily taken for a nucleolus, 
but usually it was larger, and when sufficiently magnified did 
not appear perfectly homogeneous ; all intermediate forms 
between this and others where numerous chromatin-masses 
were present could be readily found, and led to the conclusion 
that the apparently single mass is in reality composed of 
closely apposed, but not united chromatin-bodies, which sub- 
sequently separate more widely previous to the division of the 
nucleus. The chromatin-bodies are short, and with ordinary 
lenses appear like round granules, but when more strongly 
magnified are seen to be somewhat elongated. 
After they have completely separated a nuclear spindle is 
formed, the nuclear membrane having disappeared, and the 
division proceeds in the usual manner. The segments now 
undergo division, as is indicated by the evidently greater 
number of segments forming the nuclear plate (PI. XIV, 
Fig. 29 a), but owing to their extreme minuteness it is 
quite impossible to make an exact computation of their 
number. 
1 1. c. on page 244. 
