368 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
EMstology. 
There is no true cortex as such, but a dermal layer occurs in which 
chambers are very scarce, and which is filled with cells, usually stellate in 
shape. 
The whole ground-substance of the sponge is filled with particles of mud 
and débris, taken in by the sponge. This foreign matter is not specially 
frequent (or specially scanty) in any spot in the whole sponge, but evenly 
distributed throughout, so that a considerable opacity is given to sections. 
The mesogloea is in most parts scanty, but large tracts can be found here 
and there, especially in the neighbourhood of the inhalant and exhalant 
canals. The cells of the mesoglea are much fewer than those of the cortex, 
but otherwise the two tissues are very similar. In the neighbourliood of the 
canals strands of fibres are occasionally met with, which are very possibly 
muscle-fibres. The fibres run radially in direction, and form slender bands. 
in which the fibres are not closely packed together, but separated by 
gelatinous ground-substance. 
Locality. One specimen was obtained at Suez ; no locality is given for the 
other. 
Distribution. Red Sea. 
This species, as described above, approaches very closely indeed to the 
genus Huspongia, the only difference being in the eurypylous chambers. It 
is, therefore, with considerable hesitation that I have placed it among the 
Spongeliide rather than the Spongiidee ; but this course has been taken in 
order to avoid breaking up the existing classification of Huceratosa by means 
of their canal-system. Under the present conditions, therefore, the genus 
EHuryspongia is looked upon as the most highly evolved member of the family 
Spongeliidee, and possibly directly on the main stem of the evolution of the 
Huceratosa. 
At any rate, it shows how little faith can be placed in the present dis- 
tinctions between the families of Euceratosa, as intermediate forms are 
common, and almost the whole of the gaps have now been filled up. 
Another example of the same thing is shown in the two genera Heteronema, 
Keller (18), and Duriella, n. g., described below, which have been placed 
among the Spongiide on the strength of their small and diplodal chambers, 
while their skeleton is of an extremely primitive type and very irregular. 
Family SPONGIID &. 
EKuceratosa with a reticulate horny skeleton and with small more or less 
spherical flagellate chambers, commonly provided with special narrow 
exhalant canaliculi. The ground-substance between the chambers is compact 
and densely charged with fine granules. 
