394 
HYALONEMA (THALLONEMA) GEMINATUM. 
the shaft is particularly strongly bent, convex towards the spine. The terminal 
anchors are 72-100 ^ long, a fourth to a third of the whole spicule, and 175-200 n 
broad. The proportion of the length to the breadth of the anchors is 100 to 
182-257, on an average 100 : 223. The anchor is composed of from ten to fifteen 
teeth. The individual teeth are usually more strongly curved in their distal 
than in their proximal part. The extreme tips of the teeth are, if not widened 
to terminal discs ( vide infra), generally abruptly bent inward and convergent. 
A larger or a smaller number, most frequently about half, rarely all, of these 
teeth bear from one to three branches. Generally one anchor of the spicule 
is richer in branched teeth than the other. The branched teeth consist of a 
stem similar to an ordinary unbranched anchor-tooth, from the outer convex 
side of which from one to three branches arise. These branches are curved 
conformly with the stem from which they arise, concave towards the shaft, 
and usually end in oval flattened extensions, which appear as terminal discs. 
The end of the stem or main tooth, from which these branch-teeth arise, often also 
terminates with such an extension. The outer faces of the simple teeth and of 
the end-parts or terminal discs of the stem and the branches of the branched 
ones lie in a continuous surface ovoid in shape, which I take to be the inner 
face of the limit or wall of the living unit — in my opinion a single cell — 
within and by which the amphidisc is formed. As stated above, transitional 
forms with only one or two branched anchor-teeth (Plate 105 , fig. 14) connect 
these geminate with the ordinary large macramphidiscs described below. 
The ordinary large macramphidiscs (Plate 104 , figs. 6, 7) are 133-271 m long, 
most frequently about 198.5 and 204.2 n. The shaft is 15-26 n thick, generally 
straight, cylindrical, and smooth, sometimes slightly bent, and occasionally 
provided with one stout blunt spine about 20 ^ long. When such a spine is 
present the shaft is always bent as in the geminate macramphidiscs. The termi- 
nal anchors are 48-105 n long, a third to two fifths of the whole spicule, and 1 15— 
203 m broad. The proportion of the length to the breadth of the anchors is 
100 to 169-274, on an average 100 : 225.5. The anchor is composed of from 
eight to eleven teeth. The number of teeth in the two anchors of the same 
spicule is not always the same. The teeth of the opposite anchors often, but 
by no means always, alternate. The individual teeth arise nearly vertically 
from the ends of the shaft, are straight or only slightly curved in their basal 
part, but strongly curved in their distal part. The outer band-shaped portion 
of the tooth attains, in the larger forms, a maximum breadth of 25-29 m- Its 
distal end is rounded and abruptly bent inward so that the tips of the teeth 
