72 M.C. Mereschkowsky on a new Genus of Sponge. 
to the internal cavity of the sponge. This cavity passes 
without interruption through the whole body, from the basal 
cone all along the cylinder, to join the cavity of the globe, in 
such a manner that the whole organism presents us with a 
combination of a hollow cone with a hollow cylinder and a 
hollow globe. This great cavity, no doubt, corresponds to the 
gastral cavity of the other sponges, which would thus differ 
from Wagnerella (as I propose to name this sponge) only by 
their much thicker walls. ‘The average length of the peduncle 
is 0°4 millim.; in most cases it is completely straight or 
very slightly curved: by force it may be bent at a right 
angle without breaking; but the moment the pressure 
ceases it returns again to its original rectilinear position. 
The head or globe is about 0:1 millim. im diameter, making 
only one fifth of the whole length of the animal. As I 
have already stated, the head is nothing but the direct con- 
tinuation of the general cavity which passes through the 
peduncle, covered like it by a fine membrane. In fact, this 
head, as is shown by young individuals (Pl. VI. fig. 2), 
may be regarded as a dilatation of the peduncle at its 
extremity, which would render it analogous to the conical 
dilatation situated at the other extremity of the peduncle. 
he most striking character of the head is the presence 
of long and excessively fine spicules (Pl. VI. fig. 5, a-d), 
which stand out all over the surface of the ball in a 
radiating manner, and give it a spiny aspect, like that of 
a sea-urchin. It is owing to these spicules that it is im- 
possible to see distinctly the surface of the globe, and to 
determine whether there are or are not pores establishing a 
communication between the general cavity and the external 
water. The walls of the head are also furnished with small, 
short, and comparatively stout spicules (Pl. VI. fig. 6, a-c), 
only differing by their greater length from those which are 
implanted in the peduncle. Here, as in the peduncle, these 
fusiform spicules are implanted in the thin organic layer, 
so that their extremities do not project ; but their position is 
not regular in the head, the spicules being arranged in all 
possible directions, although always in a position parallel to 
the surface. 
As in all the Calcispongia, the spicules are composed of 
calcareous salts which dissolve in hydrochloric acid. Glycerine 
may also serve as a good reagent for determining the nature 
of the spicules without the necessity of destroying the speci- 
men. On putting the animal, or merely a fragment of it, into 
glycerine, it is easy to see whether the contours of the spicules 
become more distinct than when seen in water or in alcohol. 
