PROCESS OF FERTILIZATION IN THE CRAB 167 
Changes in the central body 
We now return to a more complete consideration of the behav- 
ior of the central body and the part that it plays in the explosion 
of the spermatozoon. These spermatozoa are so very small it 
is difficult, in many cases, to distinguish the central body, espe- 
cially in the live, unstained material. Some significant facts, 
however, have been observed. As is shown in figure 61, the cen- 
tral body is composed of two distinct parts, the distal part within 
the cavity of the inner tubule and a proximal part connecting 
the inner end of the tubule with the wall of the capsule. Whether 
the central body projects into the outer cavity of the inner tubule 
or ends against the shelf separating the inner and outer cavities 
of the tubule, was not definitely determined, but the latter seems 
to be the case. 
In figure 66, which was drawn from a spermatozoon in the 
tubule of the testis, fixed in Worcester’s fluid and stained in 
iron hematoxylin, the central body projects through the apex of 
the capsule. This condition may have been brought about by 
an elongation of the central body or by a shrinking of the cap- 
sule. In either case it indicates that the central body is more 
or less rigid. One should notice also that the fixing fluid has 
caused a shrinking of the nuclear cup, so that it is now more 
like a saucer than a cup. 
In figures 69 to 72, which were drawn from living spermatozoa, 
the central body projects beyond the everted tubule like a rigid rod, 
giving the impression that its elongation may have had something 
to do with the stretching of the tubule and the lengthening of 
that axis of the spermatozoon. The idea that the central body 
is somewhat rigid is further supported by its appearance in figures 
73 and 74, where it stands out above the everted tubule. The 
same condition is produced in figures 81 and 83. Probably the 
strongest evidence in favor of the rigidity of this structure is 
found in figure 75, where, in lengthening, it has pushed back- 
wards through the wall of the capsule and pushed the nuclear 
cup away from the wall of the capsule. 
