3 TO 
THE TANGANYIKA PROBLEM. 
S PONG ILL A MOORE I (R. Evans). 
This sponge grows on the shells of various mollusca, and partially covers them as 
a crust. The upper surface is raised into lobes or mound-like elevations, which in 
no case are more than half an inch above the general surface, and which are usually 
no more than an eighth of an inch above the shallow depressions which separate 
them. The surface texture of the preserved sponge is somewhat woolly in appear- 
ance, though this is probably the result of the broken condition of the dermal mem- 
brane, for it has been observed that some of the fragments preserved in Flemming’s 
fluid are smooth, and the spicules of the skeleton, though supporting the dermal 
membrane, do not in the natural condition penetrate it. 
An osculum is situated at the tip of each of the lobes or mound-like elevations of 
the surface of the sponge. This opening measures about an eighth of an inch in 
diameter, and underlying it there is a fairly large gastral cavity. The dermal pores 
are small, as usual, and are situated on the flanks of the lobes as well as in the 
intermediate depressions. 
(2) The Skeleton. — In treating of the skeleton or the supporting part of the 
sponge, first, the spicules will be described ; secondly, the arrangement of the 
spicules to form fibres, and of the fibres at large to form the skeleton, and thirdly, 
the spongin which binds the fibres together. 
(A) The Spicules. — In order to facilitate description, the spicules will be 
divided into three classes, the ordinary division into “ megascleres,” and “ micro- 
scleres” being intentionally avoided, because it is, to say the least, doubtful 
whether the small, smooth spicules are microscleres or young megascleres. 
The three classes of spicules are : — 
(a) Diactinal monaxons, which taper to a sharp point, either gradually (amphioxea) 
or more rapidly (amphitornota), and are without swellings on their shaft. The 
former are always straight, the latter curved (Fig. 1 — a.). 
(/ 3 ) Similar straight amphioxea or curved amphitornota, with distinct swellings 
on the shaft (Fig. 1 — d.). 
(7) Irregular systems formed by the fusion of spicules belonging to class a. 
(Fig. 1). 
(a) The straight amphioxea taper gradually into a sharp-pointed end (Fig. 1 — A), 
while the curved amphitornota, which are far more numerous, taper much more 
abruptly into a similar point (Fig. 1 — c. ). Both the straight amphioxea and the 
curved amphitornota are highly variable in thickness, and exhibit all stages of 
development. The axial thread is of even thickness throughout its whole length in 
all these spicules. 
(/ 3 ) In addition to being slightly more slender than the spicules already described, 
the main feature of these spicules is the presence of a number of swellings which 
varies from one to five. As a rule they are situated symmetrically with regard to 
the middle point of the spicule ; that is, if there is only one swelling it is situated 
at that point, but if there are two they are placed one on each side of that point, and 
at equal distance from it ; and similarly the symmetry is maintained when there are 
three, four or five swellings. The absence of the symmetrical arrangement, as seen 
