78 CALYCOSILVA CANTHARELLUS. 
only with a few small spines close to the end, follows the spiny region. This 
distal part of the ray is conic and tapers gradually to a rounded end, 5-17 u 
thick. This has been observed only rarely in the hexactines of C. c. var. megony- 
chia. One of the rays is thickened at the end, the terminal tyle attaining a trans- 
verse diameter of 35 yu. 
In some hexactines the rays are nearly equal in length. In most an often 
very considerable difference in length of the individual rays is to be noticed. This 
irregularity is usually due to one ray (Plate 1, figs. 16, 17, 22) or two rays 
(Plate 1, figs. 14,15) being more or less reduced in length. In the slender-rayed 
hexactines, which are probably young forms, the rays thus shortened are similar 
to the long ones. In the stout-rayed hexactines, which are certainly full-grown 
forms, this difference in ray-length is associated with and obviously correlated 
to a difference in the arrangement and shape of the spines, which renders the 
appearance of the shortened rays often very different from that of the long ones. 
The spines of the spiny regions of the long, not reduced, hexactine rays 
(Plate 1, figs. 14-18; Plate 2, figs. 4, 6, 11, 16) are conic, not very sharp-pointed, 
and 5-35 uw long. They arise quite or nearly vertically and are not very close 
together, on an average about 504 apart. In some cases they seemed to be 
arranged spirally, but I could not verify this and was indeed unable to prove the 
existence of any kind of regularity in their arrangement. The spines of the short, 
reduced, hexactine rays (Plate 1, figs. 14,15, 16; Plate 2, figs. 2, 14). are much 
closer together, often in contact with each other at the base, and occasionally 
branched. The branched spines (Plate 2, figs. 2, 14) consist of cylindroconic 
stems, the ends of which are split up into from two to four stout, conic, obliquely 
diverging, secondary spines. These spines somewhat resemble the protruding 
rays of the sterrasters of the Geodidae. 
The silicoblasts building the rays of the hexactines possess, when they start 
work, a certain amount of potential energy, E. This is expended in building the 
ray and in forming the spines. The production of the former requires the work 
W,, the production of the spines the work W2. When their task is done the whole 
of E will have been converted into work, W, and this W will be equal to W; + Wo. 
Under normal conditions there is a certain proportion between W, and Ws. 
When, however, a spicule or some other obstacle prevents the silicoblasts from 
producing a ray of the normal size, less than the usual proportion of W is ex- 
pended on W, so that, W being = W,; + We, more remains for Wo. This leads 
to the hyperdevelopment of the spines actually observed on the shortened rays. 
The ray being much shorter and the spines more numerous and on the whole 
