36 
THE VOYAGE OF H.M.S. CHALLENGER. 
Remarlcs.—Hwo specimens were obtained of tbis sponge, each measuring about 
20 mm, in diameter. 
The cortex (PL I, fig. 34) is that of a t 5 rpical Craniella, it varies in thickness from 
about 1‘27 to 1‘75 mm.; the outer layer varies from 0’16 to 0’8 mm., the inner or 
fibrous layer from 0'8 to 0’9 mm. As a rule the subdermal cavities separate the outer 
from the inner layer, but when these are absent, as happens in some places, the two 
layers pass gradually into each other. The inner layer does not difier in any essential 
characters from that of Craniella cranium, the outer, however, is distinguished by 
the presence of a number of conspicuous, round or oval bodies, ranging from 0‘09 by 
0‘05 to 0’48 by 0’32 mm,, in section they are dotted through with coloured granules, 
and, as they do not stain with reagents, they stand in strong contrast to the sur- 
rounding tissue from which, at the same time, they are sharply delimited. Seen under 
a higher magnification (PL I. fig. 35) they present themselves as parenchyma-like 
masses of polygonal cells, each 0‘015 to 0'035 mm . in diameter, with a distinct, well- 
marked cell- wall, like that of a vegetable cell; the most conspicuous contents are 
spherical, yellowish, or ochreous granules, about 0‘002 mm. in diameter, several lying in 
each cell. The remaining contents are only with difficulty discernible ; they consist of 
an unstained or only faintly stained finely granular substance, in which, besides the 
coloured granules, a spherical body 0’004 mm. in diameter, containing a spherical 
granule, occurs, and probably represents a nucleus with its nucleolus. The constancy and 
abundance of coloured granules within the cells would lead one to regard the bodies they 
compose as pigment-glands. 
The surrounding tissue, often relatively very small in quantity, is a coUenchyma, 
the matrix of which, however, stains evidently with hsematoxylin. It sometimes 
becomes fibrous, sometimes vesicular, and occasionally contains isolated oval cells pre- 
cisely similar in structure to those which compose the pigment-glands. 
The larger pigment-glands are sometimes invaded by strands of the coUenchyma, 
which penetrate into their midst. 
Briefly summarising the structure of the cortex ; most externaUy is the investing 
epithelium, beneath this a layer of dense coUenchyma, traversed by tangential fusiform 
cells, and about 0‘005 to 0’008 mm. in thickness ; then follow the pigment-glands, with a 
variable quantity of associated coUenchyma; and finally a thinner or thicker layer of 
coUenchyma, covered on its lower face with epithelium, which completes the outer layer. 
Then follow the subdermal or intercortical cavities, and beneath these the inner layer of 
the cortex, consisting of a felt of tangentially arranged fusiform ceUs, traversed by the 
cortical oxeate spicules. 
The choanosome does not contain any pigment-cells ; its mesoderm is a sarcenchyma, 
except where it surrounds the larger water canals, where it becomes a coUenchyma, the 
collencytes of which are elongated in directions radiating from the canal; numerous 
