ANDREWS: ANNULUS VENTRALIS. 
453 
it in fresh specimens, white of hen’s egg was spread over the annulus 
and then fixed to hold the sperm in place. In one whole mount of 
such an annulus the stained sperms were seen spread out in a layer 
from the suture over the promontory and also over the left tuberosity, 
though this was a left-handed annulus. In the other specimen was 
found the condition seen in figure IS (pi. 45). The sperm was fixed 
in large clots of the egg albumen spreading out from the “sperm 
angle ” across the transverse depression and along the first line of the 
zigzag and also spreading out from the second and the posterior lines 
of the zigzag. 
This is a fine demonstration of the discharge of sperm from an 
annulus subjected to pressure and it differs from the appearances 
seen in a normal annulus just after laying only in the larger amount 
of sperm actually seen. But this greater amount is to be explained 
in part by the egg albumen holding it there and in part by the fact 
that in normal laying the current of eggs and surrounding glaire 
would tend to carry off the sperm, and again, the method of prepara¬ 
tion would remove some sperm. We may suppose that the normal 
discharge of sperm would present much the same view as that seen 
in figure 18 (pi. 45). 
Since artificial pressure against the annulus forces out sperm much 
as in normal discharges and as the female appears to contract the 
muscles of the fifth somite in such a way as to produce a like pressure, 
we may conclude that it is by this muscular contraction that the female 
brings about the discharge of the sperm and the ultimate fertilization 
of her eggs. 
The sperms spreading over the promontory and adjacent areas of 
the annulus are not expanded (pi. 45, fig. 19), and probably have little 
or no power of locomotion. Their extension over the surface may be 
due to some physical phenomenon connected with the fact that they 
are imbedded in a liquid matrix that might well spread by surface 
tension. 
The actual emergence of the sperm from the annulus seems to be 
the direct result of mechanical pressure. In several experiments in 
which very strong pressure was exerted, the wax plug was noticeably 
protruded as if pressure squeezed the contents of the trumpet. In nor¬ 
mal laying, the plug remains in place but there may be enough com¬ 
pression of the trumpet to squeeze out the sperm through the surface. 
The opening of the suture may well be caused by the same pressure 
