R. W. H. ROW—REFPORT ON THE SPONGES: NON-CALCAREA. 33) 
be added during the whole life of the fibre, though no spicules seemed to 
occur just outside the spongin, as one would expect if this were the case. 
The branching of the skeletal fibre is very irregular and many anastomoses 
occur between the fibres in the deeper parts of the sponge-wall. On the 
outside of the sponge the fibres which extend furthest are often entirely free 
from any covering of sarcode, and the spicules do not project from the 
spongin. 
Outside these fibres megascleres are somewhat rare, but a few spicule- 
fibres entirely free from spongin occur. The spicules composing these fibres 
are always wholly tylostyles, exactly similar to those of the main fibres, and, 
as far as could be ascertained, in no way distinguishable from them, and they 
very rarely lie more than 5- or 6-serial in the fibres. Owing to the peculiar 
structure of the sponge-wall, no definite direction can be assigned to these 
fibres, but they nearly always have one end projecting from the sponge-wall. 
Tsolated tylostyles may also be occasionally found in the sponge, but these 
are very rare, and are not related to any definite part of the sponge. 
The microscleres are extremely numerous, and consist of small anisochelze 
and comparatively large sigmata. They are arranged quite irregularly in 
the sponge, and no anisochele rosettes occur. 
Spicules. 
A. Megascleres. 
The tylostyles referred to above are the only megascleres occurring in this 
species. They are somewhat small, straight, conical, and the shaft tapers 
gradually from the head to the apex. The head is typically Esperelline in 
shape, being oval, with the long axis of the head a continuation of the axis of 
the whole spicule. The length of the spicule varies from 0-157 mm. to 
0:21 mm., but by far the greater number of spicules approximate very closely 
to the latter measurement. 
The diameter of the shaft at its thickest point (close to the head) is 0:003 mm. 
in full-grown specimens, and very slightly under this in immature spicules. 
The head averages 0°007 mm. in length by 0°0045 mm. in greatest diameter. 
There is no difference in measurements between the tylostyles of the skeletal 
fibres and those scattered about in the sarcode. 
B. Microscleres. (Text: fig. 16.) 
(i.) Chelee. (Text-fig. 16, A.) 
The chelee occur scattered throughout the whole of the sponge, and entirely 
without orientation or definite arrangement, either in reference to the sponge 
itself or to one another. They are extremely numerous in all parts of the 
sponge. 
The chelee are palmate anisochelze of rather small size, with the “ palms” 
extremely delicate and difficult to distinguish. They measure 0-026 mm. long. 
LINN. JOURN.—ZOOLOGY, VOL. XXXI. 97 
