SEXUAL ACTIVITIES OF THE SQUID 395 
Evidently the force that causes the evagination is still the 
elastic and osmotic force in the outer and middle tunics of the 
spermatophore acting through the liquid which fills the space 
between the walls of the evaginating tube. 
The part played by the spiral filament seems to be largely, 
if not wholly, that of keeping the tube from collapsing with the 
pressure, but there may be some elastic force that aids in the 
evagination. The torsion that would be caused by the turning 
of a spiral spring might aid in the evagination, when once started, 
but there is no evidence that the filament is particularly elastic 
or partakes of the nature of a spring. The very fact that it is 
broken into minute fragments during the process of the evagina- 
tion of the tube indicates that it can have no very great elastic 
properties, and probably indicates that it retards rather than 
accelerates the evagination of this part. It is necessary that 
evagination of this portion shall not be too rapid as the sperm 
mass must gain momentum and move along at a corresponding 
rate. 
That such a filament may serve a very useful purpose in keep- 
ing the tube from collapsing or folding is evident. The freedom 
of the movements of the membranes concerned would be seri- 
ously interfered with if the tube were allowed to collapse or 
kink. The oral end of the tube does not need such a mechan- 
ism, as it is short and simple in construction and would natu- 
rally evaginate quickly with the pressure of the liquid between 
it and the outer wall. The same condition would not hold true 
for the much longer and more complicated tube that has the 
spiral filament. 
It is of passing interest to note that there is a very general 
impression among zoologists who have no personal acquaint- 
ance with Cephalopod spermatophores that this spiral filament 
is really a spring, that it is used in discharging the sperm mass 
in the same mechanical way that a spring gun discharges its 
projectile, and that the discharge is through the end of the sper- 
matophore farthest from the spring. There is, of course, no 
foundation of fact whatever for such an impression. It is simply 
arriving at conclusions from superficial appearances rather 
than by study and experimentation. 
