300 HYALONEMA (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 ^ 

 in total diameter, most frequently 65-85 ix, on an average (of 44 measurements) 

 75.3 fi. Their rays are 1.8-2.8 ix thick at the base, usually about 2 /x, 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 m 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 ^ 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 m; thickness 2.5 m; tyle 4.5 ix. 



A few microhexactines 110-120 fi in diameter with straight rays, 4-5 m 

 thick at the base, were also observed. These rare spicules were perhaps foreign. 



The micropentadines (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 fi long, 

 conic, pointed, and 2.8-3.7 n thick at the base. They bear conic, pointed spines, 

 which, in the proximal part of the ray, attain a length of 0.7 ai. Distally the 

 spines become smaller. These spicules are connected by transitional forms with 

 the canalar pinules. 



