ORGANS FOR SPERM-TRANSFER 251 
green the horny tip of canula and the shelf in the groove stand out 
clearly as distinct from the substance of the spatula. 
The canula is some 3 mm. long and at base ? mm. wide and thick. 
It is a long cone, flattened somewhat from before back, bent up- 
ward dorsally, and ending in a rather sudden point that bends 
outward from the median side. The canula is made up of both 
external and internal masses. Most of the length of the canula 
is clear, yellow, horny matter, but at the base this is continued 
as the white calcified material of the rest of the stylet. The bone 
of the external mass stops rather suddenly, while that of the med- 
ian mass is continued in the midst of the horny cap as a central 
area, as seen from the median view. An enlarged view of the tip 
of the canula, fig. 5, shows that both external and internal masses 
make about the same amount of the canula, since the groove 
continues sinuously almost to the exact tip of the organ, but yet 
there is a greater prolongation of the external mass to form a short 
ungrooved apex. This sketch is from a canula of the opposite 
side of the body from that in fig. 1. The two canular tips flare 
away from one another. 
The groove may be said to begin and to end on the median face 
and to be shoved away from it through most of its course by the 
ridge that we have called the median mass (fig. 1.). 
INTERNAL ANATOMY 
When the stylet is macerated some days the entire contents 
may be drawn out of the hard shell; such a cast of the shell has its 
general long conical form with a short conical tip that came out 
of the canula and a short flat plate that came out of the spatula. 
It is made of connective tissue and blood covered with epidermis 
with some red pigment cells and shows at the base some muscles 
and at the middle some glands. 
The muscles, as made out by dissection of fresh and preserved 
crayfishes, are weak and run from the base of the stylet into the 
adjacent ridge of the sternum upon which the stylets articulate. 
There is a wide thick fan of muscle that passes from the bony 
articular plate of the anterior face of the stylet, fig. m1. When 
