168 RAYMOND BINFORD 
There are some indications that the central body is not firm 
but a plastic, semifluid substance. This is supported by the fact 
that it sometimes glides out through the inner tubule at stages 
such as that shown in figure 76 and adheres to the surface of the 
everted tubule in one or more amorphous masses (figs. 77, g., 
79 and 82). This condition may have been brought about by 
a degeneration of the body as a result of keeping the sperma- 
tozoa in the serum of the blood or in salt solutions. Sometimes 
in unexploded spermatozoa the central body adheres to one side 
of the tubule instead of standing in the center, and it may be 
that it was only in such cases as this that it adhered to the 
everted wall of the tubule. 
Dynamics of eversion 
We may now consider the forces involved in the turning of 
the tubule and capsule inside out. We may divide this inquiry 
into two questions: (1) What are the external conditions necessary 
to initiate and carry on the process? (2) What are the internal 
conditions which respond to the external ones and determine the 
nature of the process? 
As stated above, a decrease in the osmotic pressure of the 
medium in which the spermatozoa lie, will cause the eversion. 
Unexploded spermatozoa, taken from blood serum and placed in 
5 per cent KNO;, do not explode; placed in 3 to 4 per cent KNO; 
they take the forms shown in figures 67 to 70; in. 2 to 3 per cent 
KNO,, the forms in figures 70 to 72 and 76 are obtained; in 1.5 
to 1 per cent KNO; the eversion proceeds to the stages shown 
in figures 77 to 82. Like results were obtained by treating the 
spermatozoa with dilutions of 2.8 per cent NaCl or 4.25 per cent 
NaNO;. Not all the individuals are equally affected by these 
solutions. Many of the spermatozoa retain the unexploded con- 
ditions of the capsule for a long time in a 2 per cent KNO; solu- 
tion, and often none of them attain to the stage represented 
in figure 82 when treated with 1 per cent KNO;. 
Spermatozoa kept for several days in 2.8 per cent NaCl ex- 
ploded when transferred to 4.25 per cent NaNO;. Here we had 
