19 
not sure if the latter are a distinct kind of spicules or only a 
modification of the glst. I have figured them in Plate II, fig. 38. 
In observing the surface of Isops pallida with a low power, 
you will remark two kinds of openings. The larger ones, which 
are often surrounded with a wall are probably the oscula, the 
small ones are the pores. At the description of Isops sphaeroides 
I have said that that species and the species now under description 
show much resemblance. I have figured this upper surface on 
plate IV (fig. 117). The great multitude of globulate spicules gives 
an appearance of shagreen to the Sponge. 
Sections through the Sponge show that from the centre of the 
body there are going bundles of spicules, which partly end at the 
cortical layer of globulates, partly pierce this cortex. Between the 
mashes of this skeleton is a rather compact pulpa, showing small 
and large canals. These canals seem to have a proper thin but 
strong wall, in which there are many muscle-like fibres concentiic- 
ally placed. Some of these great canals, always wrinkled, are 
placed in tangential direction, other ones are vertically to the sur- 
face. In communication with these great canals are smaller ones. 
Just under the surface there are plenty of holes (erypts, Sollas) in 
which the water enters by means of the pores. The fibrous layer 
under the globulates, is in this species and in /. sphaeroides much 
less developed than in /. phlegraei Soll. 
In his study on the Sponges of Norway, Sollas has described 
the system of canals in different Geodine-Sponges. He distinguishes 
in the cortex of @eodia Barretti five layers. 1°. a thin membrane, 
covering the whole Sponge; 2°. a layer of cells with cylindro-stel- 
late spicules”. These two are named epidermis. 3°. vesicular con- 
nective tissue-cells, 4°. the layer of globates, which are held toge- 
ther by means of fibres. 5°. the museular layer. As far as Icould 
see I found again these layers, but in different Geodidae in different 
states of development. Beneath this cortex we find in the Genus 
Isops the cortical crypts in which the water is introduced by means 
of the chonae, and passing through particular sphincters. The erypts 
are in communication with the incurrent canals, which end al, 
