394. GILMAN A. DREW 
With the opening of the tunic the portion of the middle mem- 
brane applied to the inside of the cap ruptures so that the lumen 
of the ejaculatory apparatus is opened to the outside of the sper- 
matophore and the ejaculatory apparatus immediately begins 
to evaginate because of the pressure on the inside of the sper- 
matophore (fig. 5) The evagination of that portion of the 
ejaculatory apparatus which is oral to the spiral filament is so 
rapid in the untreated spermatophore that the eye cannot follow 
it, but in the specimens treated with magnesium chloride it may 
be slowed down so the gradual evagination can be followed easily. 
As the ejaculatory apparatus evaginates, the diameter of the 
tube is greatly increased and the walls are correspondingly 
thinned. 
There is a distinct pause in the evagination when the region 
of the spiral filament is reached (fig. 6). This is probably 
largely due to the stiffness of the filament itself, but may be 
influenced by the fact that other membranes are involved at 
about the same point. 
Evidently the evagination of the first part of the ejaculatory 
apparatus is due to the pressure of the liquid between the mid- 
dle and inner tunics that is in the oral end of the spermatophore. 
This is shown by the fact that the action is so rapid and by the 
further fact that the cement body and sperm mass are drawn 
away from each other (fig. 6). The sperm mass lags behind, 
so the connection between it and the cement body is stretched 
to its full extent. 
After an instant’s delay when the region of the spiral filament 
is reached, the tube continues to evaginate. The evagination 
here is continuous, but not nearly so rapid as the first part. 
the evaginated portion of the tube increases greatly in diameter, 
the walls become correspondingly thinner and the spiral fila- 
ment is broken into minute fragments which continue to adhere 
to the outside of the evaginated tube, (fig. 7). As this process 
goes on, the free edge of the outer membrane adheres to what 
is now the inside of the evaginated middle membrane and is . 
reflected so that this membrane, together with the inner tunic 
with which it is associated, is turned inside out (figs. 7 and 8, 
OM and IT). 
