ORGANS FOR SPERM-TRANSFER 283 
triangle had been. Apparently the wedge of the triangle is well 
fitted to hold the liquid in the tubule since it fills up the groove 
external to it (fig. 9), where the sides of the groove are not as close 
together as they are distally (fig. 10), which is beyond the wedge. 
When the ink had been introduced into the tubule and not forced 
out of the tip of the stylet the triangle was applied to the stylet 
and the radius worked back and forth like a piston in the tubule 
with the result that some of the ink issued from the tip of the can- 
ula of the stylet. 
This suggested that the radius might act like a piston in normal 
sperm transfer and thus propel the sperm from the papilla along 
the tubule to the annulus. We also saw that when a pair was 
separated in conjugation the sperm that issued from the tip of the 
canula of the stylet was mixed with bubbles of air when held out 
of the water, which suggested some action at the base of the tubule 
(at the orifice) to draw the air into the tubule. However, this 
might be movements of the triangle or simply failure of the tri- 
angle to hold a tight joint around the tip of the papilla and ori- 
fice, for thus air could be drawn in by the stream of sperm ad- 
vancing, driven by pressure of the muscles of the deferent duct. 
When the radius was inserted into the orifice and shoved along 
in the tubule, sperm was forced out of the tip of the canula, which 
seemed to demonstrate the ability of the radius to act as a pro- 
pelling piston. 
We failed to detect any such piston motions during conjuga- 
tion, but they would be of very slight extent and not readily 
observed. The movements of advance and recession described 
above are of a much grosser magnitude than the piston movements 
that might be supposed to take place. The movements 31, 30 
are only for getting right adjustment of the enveloping triangle 
over the papilla tip and the entrance of the radius into the tubule 
so that the hand-like triangle may make such tight binding of the 
papilla to the orifice that no sperm escapes or comes into contact 
with the water. Yet the piston may then presumably be in posi- 
tion to advance or recede a little. When we thrust the triangle 
strongly so far along the stylet that the elbow was at the orifice, 
(fig. 30), the triangle tended to spring slowly back out of the groove 
