PROCESS OF FERTILIZATION IN THE CRAB LA 
tubular cavity becomes everted. Portions of the central body 
often adhere to the wall of the tubule and are carried outward 
and so mark the extent of this second eversion (fig. 77, g.). 
Stage 4. The third eversion of the tubule, accompanied by the 
inversion of the capsule (figs. 80 to 82). The internal pressure 
continues to increase, as is shown by the bulging out of the 
walls of the everted portion (figs. 78 and 79). This brings a 
strain upon the axis in which the tubule and central body lie. 
This tends to stretch these structures as is shown by the incurv- 
ing of the apical wall of the everted portion in figures 78 and 79. 
This causes the base of the everted part to press on the sides of 
the capsule. This pressure on the sides of the capsule, together 
with an up-pulling along the line of the central body, results in 
turning the capsule through the collar when the last section of 
the tubule is everted. In figure 82 the portions of the everted 
wall contributed by the second, third and fourth stages of the 
eversion are probably indicated by the granules g! and g?. Thus 
we see that the whole transformation may be explained by the 
increase of pressure in the capsular cavity together with tensions 
along the line of the inner tubule and the central body. 
Efforts were made to reverse this process by placing sperma- 
tozoa in very concentrated solutions of the salts used. The only 
effect of this treatment was a shrinking of the everted portion, 
which would again swell up and the process of eversion continue 
when dilute solutions were again used. After the explosion had 
reached the stage presented in figure 82 the only part affected 
by concentrated solutions was the protoplasmic portion at the 
bottom. It is also true that this is the only part that takes 
methylene blue, methyl green or thionin stains when these are 
applied to the living spermatozoa. It was rather surprising that 
the contents of the everted capsule were not stained by these 
stains. Sometimes a few granules can be seen in this cavity. 
Figures 73, 74, 84 and 85 were made from spermatozoa which 
had been kept in a 5 per cent KNO; solution for fifty-one days. 
We observe here that partial explosion had taken place. Those 
shown in figures 84 and 85 had reached the stage corresponding 
to figure 70. When these were treated with a solution of lower 
