276 E. A. ANDREWS 
gives the wide scalene triangle as seen from the median side (fig. 
v1). The proximal elongation of the cylinder makes the elbow of 
the triangle, while the distal elongation has made the pyramid 
or wedge that runs up toward the flagellum of the endopodite. 
As yet no setae were seen on the wedge. The triangle, however, 
is not merely a flat plate that grows out diagonally, but from the 
first it is thick through in the anterior-posterior direction, thus 
producing the cylindrical edge seen in fig. 27, where the thick edge 
is restricted and marked off by a less thick neck; moreover the 
thickening of the cylinder is toward the anterior face. By the 
stage shown in fig. 28 there is great thickening toward the external 
face. Moreover the external free edge of this thickened cylinder 
is now itself thickened as a ridge hanging out from the ventral 
rim over the depressed area as indicated by the broken line in fig. 
28. This rounded thick edge is the future radius. (Compare 
figs. 28 and vu.) From this state it is an easy transition to the 
more sculptured form of the appendage seen in adults. 
The second pleopods of the male thus owe their special struc- 
ture to a gradual emphasis of the endopodite and protopodite with 
the addition of an outgrowth peculiar to these appendages, the 
triangle. The triangle at first is a mere blister on the median 
side of the endopodite but soon becomes an oblique plate that is 
surmounted by a thickening. The plate grows anteriorly and the 
thickening of its free edge becomes longer than the base of the 
plate, with a resulting triangular form as seen from the median 
face. The thick ridge grows out externally and this extension 
itself acquires a thickened rim, posteriorly, which is the radius. 
The triangle is thus a triangle only as seen from the median 
face of the pleopod, in its entirety the triangle is a curved object 
like a half open hand, and as such is capable of being applied to 
the rounded surface of the first stylet. It is made of a cylinder 
obliquely set along the edge of a plate and curving over it, like 
fingers over the palm. A slip of paper if cut of angular form and 
bent twice at right angles may be made to represent the stylet. 
