2 
N. ANNAN DA LE. 
are particularly mimerons in the neighbourhood of gemmules and sometimes form regulär 
cages eitlier round single gemmules or round groups of gemmules. These cages consist of 
spiculés lying more or less parallel 
to one another in a membrane of 
spongin. 
Spiculés. The megascleres are 
small, slender, sharply pointed and 
smooth; they vary greatly in diameter, 
those tliat lie free being as a rule 
much less slender and also somewbat 
shorter than those that form the fibres. 
The latter, however, are usually less 
slender near the base of the sponge 
than they are in its upper parts, and 
the spiculés of each fibre are appro- 
ximately of the same size. Free micro- 
scleres occur in the dermal membrane 
but are absent from the parenchyma. 
They are very small and slender, 
sharply pointed at the ends, covered 
with minute straight spines and some- 
what spindle-shaped in outline. The gemmule spiculés are stouter and eitlier abruptly 
pointed or blunt; the spines at and near the extremities are 
larger and more numerous than those in the middle part of the 
spiculé and often exhibit a tendency to be retroverted and form 
rudimentary rotules such as are not uncominon in the gemmule 
spiculés of Spongilla lacustris and other species of the genus. 
Gemmules. The gemmules are variable in size. In form 
they are spherical. The pneumatic coat is often very thick and 
contains very minute and comparatively few airspaces; there is 
sometimes a long cylindrical foraminal tubule. The spiculés are 
arranged tangentially in the pneumatic coat and are not very 
numerous. The gemmules lie free in the substance of the sponge 
and ar not bound together in groups although several are often 
enclosed in a single cage of megascleres. 
«Habitat. Small lakes in the valley of the R. Pyderata, 
tundra of Ре -mal, Governement of Tobolsk. 19. VIII. 09». 
The most remerkable feature of tliis sponge is the structure 
of its skeleton, a feature in which it appears, to judge from 
