6 j PERCY SLADEN TRUST EXPEDITION 
metamorphosed collared cells. It is true that they are considerably larger than the latter 
and differ much in structure, but their arrangement in the mesogloea and the fact that 
there are no other collared cells in the sponge are very suggestive. It is possible that 
they may be concerned with the nutrition of the large ova, whose staining reactions are 
so curiously similar. I would suggest that the sponge having become full-fed, and the 
reserve material being stored up in the collared cells, the latter migrate inwards and are 
ingested by the probably amceboid ova. During this process the sponge becomes con- 
tracted and its ordinary activities suspended. The collared cells are probably replaced 
again later on by metamorphosis of amcebocytes, which at first line the gastral cavities as 
a flattened epithelium. 
The idea that the yellow bodies may be symbiotic alge also naturally suggests 
itself, but their chemical reactions and the fact that they contain no nuclei appears to 
me to be fatal to this view. I have also compared them carefully with the ‘‘ yellow 
granules” of Leucosolenia (Clathrina) coriacea, but the latter are very much smaller 
and obviously quite different. 
Genus Drenpya Bidder. 
Sponge colony consisting of a large central individual lined by collared cells, from 
which radially arranged diverticula are given off. Skeleton composed of equiangular 
triradiates, to which quadriradiates may be added. Nuclei of the collared cells probably 
always basal. 
This genus was proposed by Bidder [1898] for Carter’s Clathrina tripodifera, of 
which I gave a full account in my Monograph of Victorian Sponges, Part I [1891]. 
Hitherto this has remained the only known species, but I have now to describe a new 
and very interesting form. 
2. Dendya prolifera n. sp. 
(Plate 1, figs. 3, 4; Plate 3, figs. 4, 5.) 
The single specimen of this very interesting species is unfortunately in a very poor 
state of preservation, especially as regards histological characters. It has now the form 
of a flattened sac (Plate 1, figs. 3, 4), but how far the flattening may be due to artificial 
compression I am not prepared to say. The sac is much broader at one end than at the 
other and the vent is situated at the narrow extremity. It is also slightly curved, with 
one margin convex and the other concave. The broad end has been artificially truncated, 
so that the central gastral cavity opens widely to the exterior at this end as well as at 
the vent. A good deal of the wall of the sac has also been torn away from one side. 
There is no indication of dorsiventral differentiation of the two flattened sides and the 
sponge probably grew either erect or pendent. 
The thickness of the wall of the sac is very irregular and the surface very uneven, 
owing to the development of the very numerous proliferating radial tubes. These tubes 
-are for the most part arranged in dense bunches, between which the thin, translucent 
gastral membrane is in many places plainly visible from the outside, especially in the 
neighbourhood of the vent, where it forms a thin oscular membrane or collar. 
