300 
HYALQNEMA (PRIONEMA) FIMBRIATUM. 
and very stout spicule-fragments found within the stalk-protuberance make 
it probable, however, that either these anchors are not the sole stalk-spicules, 
or that the proximal, smooth end-parts of the anchor-shafts are very greatly 
increased in length and in thickness during the process of further growth, which 
leads to their distal parts being pushed out from the body to form the protruding 
stalk. 
The six rays of the microhexactines (Plate 60, figs. 25-30; Plate 62, figs. 
42-45) are usually fairly equal; more rarely two opposite ones exceed the other 
four markedly in length. The microhexactines with equal rays measure 56-95 n 
in total diameter, most frequently 65-85 n, on an average (of 44 measurements) 
75.3 n. Their rays are 1.8-2. 8 n thick at the base, usually about 2 m, conic, and 
attenuated to fine points at the end. They bear rather sparse, minute spines. 
The spines of the basal and middle-parts of the ray are usually 0.2-0. 5 n long; 
distally they become smaller. The basal half or so of the ray is quite straight, 
the distal part curved. Where the straight basal part passes into the curved 
distal part an abrupt, sometimes quite angular bend is often discernible. The 
curvature of the distal part is very considerable, the direction of the end-part 
diverging up to 120° and more from the direction of the basal part. The direc- 
tion of curvature of opposite rays is usually opposite, so that any two opposite 
rays together generally form an S-shaped curve. 
The rare microhexactines with two opposite rays exceeding the other four 
in length measured were 80-90 n long and 40-50 n broad. In these spicules 
the two opposite, longer rays are not so strongly curved as the four shorter ones. 
In a spicule-preparation I found a monactine microhexactine-derivate 
which appeared as a minutely spined tylostyle with strongly bent pointed end. 
Its measurements were: — chord 57 n] thickness 2.5 n', tyle 4.5 n. 
A few microhexactines 110-120 ^ in diameter with straight rays, 4-5 m 
thick at the base, were also observed. These rare spicules were perhaps foreign. 
The micro pentactines (Plate 60, figs. 31-34; Plate 62, fig. 28) consist of 
one slightly longer apical and four shorter lateral rays, which latter are fairly 
equal in size and extend in a plane vertical to the apical ray. The rays of these 
spicules are straight in their proximal and curved, generally very considerably, 
in their distal part. Opposite lateral rays are curved either in the same or in 
different directions. The rays are, measured along the chord, 35-79 ju long, 
conic, pointed, and 2. 8-3. 7 m thick at the base. They bear conic, pointed spines, 
which, in the proximal part of the ray, attain a length of 0.7 fx. Distally the 
spines become smaller. These spicules are connected by transitional forms with 
the canalar pinules. 
