C. L. Edwards 
269 
J. Polian Vesicles. 
As a general rule the Polian vesicles are club-shaped and may be simple or 
branched (Fig. B, S, Bi), coming ofif from the water- vascular ring as solitary 
vesicles, or so close togetlier that it is difficult to determine the separate origins of 
some, or all, of the vesicles of a group. 
Fig. B. Water-vascular ring with Polian vesicles and stone-canals. M, Mid-dorsal mesentery. 
Eadial canals ; RD, riglit dorsal ; RV, right ventral ; MV, miJ-ventral ; LV, left ventral ; 
LD, left dorsal; R St C, L St C, right and left stone-canals; S, simple, Br, Branched, Br Tuft, 
tuft with branched vesicles, x 5^. 
Such a group, when made up of simple vesicles, I have called a tuft (Fig. B, 
Tuft). When some, or all of the vesicles, are branched and arise either from the 
base of one of the vesicles of the group (Br Tuft) or directly from the water- 
vascular ring, it is a tuft with branched vesicles. 
There are two principal groups of Polian vesicles in the region opposite the 
bases of the right and left ventral radial canals with small tufts and solitary 
vesicles in the ventral region between (Fig. B). Sometimes, as in 75 (Table II.) a 
Polian vesicle may have its origin near the dorsal mesentery, and again they may 
come off from the entire extent of the water-vascular ring. In S (Table I.) one 
Polian vesicle arises from a radial canal between the tentacle and water-vascular 
ring, and in 40 one large vesicle arises from the right dorsal radial canal just below 
the calcareous ring. 
The most interesting case is specimen 17, which has a total of 92 vesicles and 
branches of which 32 are solitary, and of these, 3 have each 1 branch. There are 
9 tufts ranging from 2 — 7 vesicles in a tuft. In addition there are 2 tufts with 
branched vesicles ; the first with 2 simple vesicles and 1 with 1 branch, 1 with 3 
and 1 with 4 branches. 
