SPINDLE-LENGIH AND CELL-VOLUME. 47 
undivided to one pole. The primary and secondary spermatocyte 
cells of Yorficula auricularia are respectively represented by 
figs. 13, 14 and 15, 16, 17. Figs. 18 to 21 show the primary 
spermatocytes of Helix pomatia, and the secondary spermatocytes 
are shown in figs. 22 to 24. 
Now, exact measurements of cell-volumes cannot be made; but 
it is evident from the photographs that, in the metaphase, the 
primary spermatocyte cells of Zvriton cristatuws, Stenobothrus 
viridulus, S. curtipennis, and Helix pomatia differ from one 
another only slightly in size, and are considerably larger than 
those in Forficula auricularia. Moreover, drawings sent to me 
by Dr. von Winiwarter show that in Man these cells are smaller 
than those of Z'riton, Stenobothrus, and Helix. And the same 
results are obtained if we compare the secondary spermatocyte 
cells. 
In the circumstances, we must realise that cells of these two 
generations may be of similar sizes in widely separated crganisms, 
and of very different sizes in organisms that are closely allied ; 
and increasing somatic complexity of the organism is not 
necessarily accompanied by increase of the volumes of these 
cells. 
The Length of the Mitotic Spindle at the Conclusion of the 
Spermatocyte Metaphases of Helix pomatia (Pl. II. figs. 18—- 
24) and Forficula. auricularia (PI. II. figs. 13-17). 
We will deal first with spindle-lengths in Helix pomatia. 
Figs. 18 & 19 are polar views of the equatorial plate in the 
primary spermatocyte metaphase. Figs. 20 & 21 are lateral 
views, showing constriction of the chromosomes in progress. 
I estimated the spindle-length at the conclusion of this meta- 
phase to be 15°3 w; and, since the length found from these two 
photographs for the slightly earlier stage is 15 4, my original 
measurement seems to have been accurate. 
Fig. 22 is a polar view of the equatorial plate in the secondary 
spermatocyte metaphase. Fig. 23 is a lateral view of the spindle 
at the conclusion of this metaphase. The spindle-length at this 
stage was said to be 12:1 u, and this measurement is now verified ; 
for I am not attempting in this paper to express spindle-lengths 
in terms smaller than half a micro-millimetre, and the length 
found from the photograph is 12 yp. Fig. 24 shows a slightly 
later stage, when the anaphase has begun; the length of the 
spindle in this cell is found to be 12°5 pe. 
Let us now consider the spindles of Forficula auricularia. 
Fig. 16 is a polar view of the secondary spermatocyte complex ; 
ten chromosomes are arranged on the periphery of the spindle, 
and two lie within it. Figs. 15 & 17 are lateral views of this 
mitosis; the chromosomes are constricting in the equatorial 
plane, and the stage depicted therefore immediately precedes 
the conclusion of the metaphase. The length of the spindle, 
