24 
HOLASCUS EDWARDSII. 
The rare styles and tylostyles of the root-tuft, which, as above stated, may 
be foreign to the sponge, are covered with spines, and near the distal, rounded 
end 12-17 n thick. The distal end itself is either simply rounded off or, more 
frequently, thickened to a terminal tyle, with a maximum transverse diameter 
of 32 fj.. 
The anchoring spicules (Plate 20, figs. 5-20) are anisoactine rhabds. I 
did not observe any long intact ones. The longest fragments observed were 
45 mm. in length. The morphological centre, the position of which is clearly 
marked by a well-developed axial cross (Plate 20, figs. 5-8a) is only 137-200 ^ 
distant from the distal end of the spicule. Thus, whilst the proximal ray may 
attain a length of over 40 mm., the distal ray is usually less than 0.2 mm. long. 
Proximally the spicule is gradually attenuated to a fine point. Distally it 
thickens, and it attains its maximum thickness some distance beyond the middle 
of its length, long before the morphological centre (axial cross) is reached. 
Beyond, it again becomes thinner, and near the distal end, at the thinnest point 
between the morphological centre and the terminal anchor, is 7-11 n thick, 
about two thirds to three quarters of what it measures in the middle. At the 
distal end the spicule is thickened to a terminal tyle. 
The proximal part of the spicule (Plate 20, fig. 11) is perfectly smooth. 
Somewhere about the middle of its oblique length, backwardly directed spines 
begin to make their appearance; these usually enclose an angle of 20-30° with 
the axis of the spicule. At first (Plate 20, fig. 12) these spines are very small 
and far between. Farther on (Plate 20, figs. 13, 14) they become larger and 
more numerous, and they continue to increase in number and size quite up to 
the morphological centre (axial cross). On the distal ray the spicule has four 
to seven spines every 100 n (Plate 20, figs. 5-10, 15-20). In the middle of the 
spicule the spines are uniformly scattered and not arranged in groups (Plate 20, 
figs. 13, 14). Towards the distal end they tend to form verticillate clusters 
(Plate 20, figs. 5-8, 15-20), two of which are particularly pronounced, one situ- 
ated at the morphological centre (axial cross) (Plate 20, figs. 5-8a), the other 
at the end. Together with the terminal tyle this second cluster of spines forms 
the anchor. 
The large spines of the distal part of the spicule are 10-30 /x long and 4-7 n 
thick at the base. The terminal ones, which form the anchor-teeth, are similar 
to the others, but somewhat stouter. 
The anchor appears as a conspicuous terminal thickening with an outline 
closely resembling an inverted gothic arch. From the proximal side of this 
