8 
THE TANGANYIKA PROBLEM. 
SPONGILLA TANGANYIKA (Evans). 
Owing to the fact that there was but a small piece of this sponge among the 
material collected, it is impossible to make any statements with regard to its external 
form, but it must have been closely similar to that of Spongilla moorei, otherwise 
the difference would have been detected. But although thus, the two sponges are 
similar to one another in their habits of growth ; they are strikingly dissimilar in 
the characters of their individual spicules, though the general arrangement of the 
spicules in the fibres and of the fibres at large is strikingly alike. 
The description of this species must, of necessity, be brief. The same plan will 
be followed, as far as possible, as in the case of the description of Spongilla moorei. 
(1) The skeleton will be described under the following headings : — 
(A) Spicules. 
(B) Arrangement of Spicules, etc. 
(C) Spongin. 
(A) Spicules. — It may be safely stated that there are megascleres and microscleres 
in this sponge. The megascleres consist of amphistrongyla and amphitornota, 
which are, for the most part, thickly covered with small spines. In addition to 
these there are a few smooth or sparsely-spined amphioxea (Fig. 3 — b.). The 
microscleres are much slenderer than the megascleres, though they almost equal 
them in length. They are always smooth and slightly curved (Fig. 3 — a.). 
(B) The General Arrangement. — The arrangement of the spicules does not 
differ materially from that already described in Spongilla, moorei. The spiny 
amphistrongyla and amphitornota, together with a few smooth or sparsely-spined 
amphioxea, are arranged with their axes parallel to one another to form the skeletal 
fibres. These divide and again reunite, producing an arrangement which is usually 
described as being reticulate. The fibres are connected together in many places by 
spicules which bridge over the intermediate spaces. These spicules are the largest 
in the whole sponge, as a rule, as was found to be the case in Spongilla moorei. 
In addition to these there are many spicules, both spiny and smooth, which appear to 
lie about more or less freely in the tissues. The slender microscleres are nowhere 
connected with the fibres, but lie absolutely free in the tissues. 
(C) The Spongin. — The spongin is not so highly developed in Spongilla 
tanganyikic as in Spongilla moorei. The former, therefore, in this respect resembles 
more closely the ordinary species of Spongillidce than the latter appears to do. The 
spongin does not appear to extend to the surface, and the layer which covers the 
fibres is correspondingly thin. The greater development of spongin occurs at points 
where the fibres branch or reunite, and at the places where the connecting spicules 
penetrate the fibres. 
(2) The Gemmule. — Though there was but a small piece of this sponge, it 
happened to contain several gemmules. These are devoid of spicules, but are 
surrounded by the ordinary skeletal spicules and the microscleres ; they possess a 
thin coat, as in Spongilla moorei , and are spherical and of small size. As regards 
their cellular contents, they present the ordinary characters of ihe Spongillid 
gemmule. 
