PROCESS OF FERTILIZATION IN THE CRAB 153 
that the spireme has the appearance of a brown thread with 
granules distributed irregularly along it (fig. 9). The diameter 
of the granules is slightly greater than that of the thread between 
the granules. The spireme now becomes shorter and thicker and 
is finally massed at one side of the nucleus in the condition of 
synapsis (fig. 10). This stage persists for a comparatively: long 
period. The spermatocytes enter synapsis irregularly, in a sort 
of one-at-a-time fashion but they tarry here until all of the cells 
in the greater part of the tubule have reached this stage; then 
the nuclei of a given portion all proceed to the open spireme 
stage, shown in figures 11 and 12. These figures show only the 
chromatin which lies on the side from which the nucleus was 
observed. The chromatic material is again arranged in the 
peripheral portion of the nucleus and is segregated into the chro- 
mosomes which become somewhat massed in the center of the 
nucleus. The spindle next makes its appearance (fig. 13) and 
the chromosomes are drawn into the equatorial plate (fig. 14). 
The mitotic figure represented in figure 15 shows the possi- 
bility of a tri-polar division. Such a condition may have been 
brought about by the formation of one of the spindles of the 
second division before that of the first division was completed. 
There is a small portion of the chromatin of this nucleus which 
is not involved in the mitotic figure. This portion is shown at 
e., in figure 15 a, which is a drawing of what was seen at a lower 
level than that shown in figure 15. 
The chromosomes in these nuclei are so small and so closely 
crowded together it is very difficult to determine their structure 
or their number. In one preparation, however, I obtained a 
ring-shaped appearance of the chromosomes (fig. 16). These 
forms were seen in the equatorial plate and also before the chro- 
mosomes had been arranged in the plate. In most of the prep- 
arations the chromosomes appear as mere granules. It may be 
that the ring-shaped forms were produced by the fixing reagent, 
which may have caused a swelling of the chromosomes. This 
result was not always obtained, however, by the same reagent. 
When destaining is carried so far as to remove all the stain 
from the cytoplasm and the achromatic figure, the equatorial 
