CELL SIZE AND NUCLEAR SIZE 21 
von neuem zu ernihren, um abermals heranzuwachsen und sich 
zu teilen.”’ I have tried to make measurements at the stage 
described by Hertwig, but find that in these segmenting eggs it 
is too ill defined to be safely used. Between successive divisions 
the nuclei are growing continuously and rapidly and there is no 
clearly marked pause in the nuclear growth; accordingly slight 
differences in the stages chosen for measurement show relatively 
large differences in the sizes of the nuclei. 
In order to take a stage intermediate between the two ex- 
tremes of nuclear size, and in which the nuclei may be regarded 
as having reached a normal functional condition, not related 
primarily to the preceding or succeeding division, I have chosen 
that stage when the nuclei first become regularly spherical in 
shape. For a considerable part of the resting period the nuclei 
are elongated at right angles to the previous spindle axis, and 
in the plane of the chromatic plate of the previous anaphase; 
during the latter part of the resting period they grow very rapidly 
in preparation for the succeeding division (‘ Kernteilungswachs- 
tum’ of Hertwig). The stage when the nuclei first become spher- 
ical lies somewhere between these two phases and may therefore 
be considered to represent the mean nuclear size. However this 
stage is not so precisely defined as are the stages of maximum 
and minimum nuclear size, and therefore the nuclear dimensions 
are likely to be more variable. 
It is obviously more difficult to determine the volume of the 
cleavage cells during the resting period, when they are pressed 
into irregular and polygonal forms, than during mitosis when they 
approach a spherical shape. However the approximate accuracy 
of the cell dimensions recorded in table 5 may be judged by com- 
paring them with the maximum and minimum cell dimensions, 
given in tables 3 and 4. 
The Kernplasma-Relation varies about as much for mean 
dimensions of the nucleus and cell as for maximum ones, though 
not as much as for minimum dimensions. In yolk-containing 
cells it varies from 1: 1.1 to 1: 27.5 and in purely protoplasmic 
cells from 1:7 'to 1:35.7. 
