256 E. A. ANDREWS 
calcified part of the shell fades away and only pure chitinous 
matter is left, so that a section at the very tip of the canula, (fig. 
13) is only chitin. This view is enlarged four times as much as 
the preceding one and shows the disappearance of the superficial 
part of the groove though the bottom, which is now close to the 
surface, is still overhung by the shelf from the external mass. 
That is the tube at the bottom of the groove can now discharge 
by a slit to the surface at the tip of the canula; see fig. 5, where the 
surface slit of the groove is represented by the black line and the 
bottom of the groove, or the tube, is represented by the dotted 
line, which comes finally to the surface at the tip as seen in the 
section across the level 13. As fig. 5 is of-a right stylet and the 
section 13 from a left stylet it shows the parts reversed; the main 
bulk of the section is really of the external mass, as in fig. 12. 
The specialization of the bottom of the groove had not been 
expected till sections revealed it and suggested some special use. 
Sections of stylets taken when being used in conjugation soon 
showed that the tube at the bottom of the groove is the channel 
for the transfer of sperm. Along this minute tube all the sperm 
passes from the papilla to the sperm pocket of the female. A 
section across the stylet where the median surface bears a tuft 
of setae, between the levels of 8 and 9 of fig. 6, when sufficiently 
enlarged, shows that the sperm is contained inside the tube of the 
groove, as in fig. 14. This shows only the part of the shell about 
the tube, with the sharp edge of the shelf above, jutting out to 
almost meet the wall of the median mass (see fig. 9). The cavity 
of the tube is full of a secretion containing at its centre a pear- 
shaped mass of the peculiar sperm of the crayfishes. As was 
shown (6) these sperm do not assume the star shape they have in 
books as long as they are in the male and not even when in the 
sperm receptacle of the female when normally protected from the 
water, and in this section, where they are seen in transit, they 
are still spherical, clear bodies with the peculiar bowl-shaped 
central part that, as represented in the sketch, might be thought 
a central nucleus. All along the groove above the orifice thereis 
thus a strand of sperm surrounded by a paste-like white mass 
that fits tightly into the tube. 
