ORGANS FOR SPERM TRANSFER 263 
the notch, or orifice, and bears a tuft of short setae. The spatula 
is long, flat and pointed. The canula is bluntly pointed and 
turned outward. 
Later when the animal is 64 mm. long, the false joint of the 
stylet has disappeared and the tips become more sharp and long. 
Even before this size the males are known to conjugate, when 
about two inches long. 
We thus find that the complex stylet of the adult starts from 
a slender papilla that becomes slightly flattened and grooved so 
as to form a very clumsy spoon with its depression rather more 
median than ventral. Then the sides of this groove grow up and 
make the groove into a cleft, which opens as before toward the 
median face proximally and distally; but along the middle of its 
course is forced to open ventrally and even externally by the over- 
hanging growth of the median mass. The organ might be imi- 
tated by taking a long strip of clay with a slight length-wise groove 
on it and rolling the sides up over the groove, the median side 
tending to roll over outside the other. How the shelf from the 
external mass first grows out over the groove to cut off its inner 
part as a tube was not made out, but it is evidently a secondary 
specialization of the shell made by some special activity of the epi- 
dermis in a line near the bottom of the groove after the groove has 
become deep. 
THE SECOND OR ACCESSORY STYLET 
The accessory stylets (figs. v-vir) are evidently specializations 
of the common type of abdominal appendages, (fig. 26). They 
are elevated only when in use in conjugation; and at rest are car- 
ried forward under the thorax, horizontally, where they rest upon 
the first stylets and are closely packed in with them inside the 
special sternal groove of the male thorax. 
Figs. v, VI, VII, vi, represent the left second stylet as seen from 
the ventral or posterior, the median, the anterior or dorsal, and 
the exterior faces, respectively. Like the unmodified pleopods 
this has a basal protopodite, an exopodite, an endopodite. The 
exopodite is a slender offset with setae, while the endopodite is 
