ORGANS FOR SPERM-TRANSFER 279 
toward tip of groove. The second forms a mechanical brace 
tending to hold the first from going backward. 
In order to separate the two the second must move toward the 
animal and glide along the first till free from it. And this motion 
is actually seen. The locking is not always done without trial 
and may be broken and renewed during conjugation, so that 
we often see two positions of the stylets, that of perfect locking, 
Fig. 31° Same view when the accessory is drawn back into position of recession 
showing the papilla at the mouth of the groove. 
as in figs. 29 and 30 when the triangle is most advanced toward 
the tip of the spiral, and a preliminary and alternate position of 
recession when the triangle is applied against the base of the first 
style proximal to the orifice. ‘This position of recession is shown 
in fig. 31. The triangle goes as far toward the basal end of the 
first stylet as possible, till stopped by the knob on the base (fig. 
11). In this recession the orifice with the papilla meeting it, is 
exposed and the ventral lip is seen. 
It should be borne in mind that the back and forth play of 
the triangle on the first stylet is limited not only by the knob 
basally and the narrowness of the groove that prevents the radius 
from going into it dorsally beyond the position of figure 30, but 
it is limited laterally by the fact that the triangles of the two sides 
