280 E. A. ANDREWS 
of the body are in contact and are held together by being placed 
in the squarish hole between the necks of the first two stylets. 
The two triangles play back and forth like two hands with bent 
fingers, back to back, in a narrow space between the first stylets 
and, like hands, each runs its palm or soft flat surface along the 
median constricted part of the first stylet and the firm guiding 
ridge—its thumb, as it were—along the external face of the stylet 
(fig. 29). In one case from 3 to 4 seconds were taken to glide the 
triangles back from the normal position to the recession (fig. 31) ; 
there they remained four or five seconds and advanced strongly 
in two seconds. Another recession took 12 seconds, but the ad- 
vance occupied 2 seconds. 
If we imagine figure v applied to 1, vi to 1 and vu to 11, 
vil to Iv, we will appreciate how nicely all the surfaces adjust 
themselves. The oblique ridge of the external mass of fig. I is 
overlaid by the soft depressed area, (figs. vill, 22) so that the 
thumb-like guide shows external to the ridge as in fig. 29. 
In life the two sets of appendages, right and left, are so closely 
applied together that the median face of neither can be seen, 
directly, without mutilation experiments on one side, but the pres- 
ence of the guide ridge along the external face of the spiral (fig. 
29) enables one to judge where the triangle must be at any stage 
of advance or recession, a matter of importance in deciding as to 
its use in sperm transfer. 
That an application of the second, or accessory stylet, to the 
first is necessary for the completion of normal conjugation and the 
filling of the sperm pocket by transferred sperm, was determined 
not only by the above facts of structure and use but by the follow- 
ing experiments. The instincts of the male are so strong that, 
when in the process of conjugation the second stylet on one side 
was cut off, there was no immediate visible effect, except the 
escape of some blood from the stump of the appendage. And- 
when on the next day al] the stylets, both first and second, were 
cut off, the male seized and turned a female and carried the 
conjugation as far as possible in the absence of the organs of 
transfer. The instincts thus go on without the means of carrying 
them to completion. 
