3 i8 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 vioorei, 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 characteis 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. 



The skeleton will be described under the following headings : — 

 (A) Spicules. 



Cb) 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.). 



CB) 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, w hich 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. 



' The Spongin. — The spongin is not so highly developed in Spongilla 

 tanganyika as in Spongilla moorei. The former, therefore, in this respect resembles 

 more closely the ordinary 7 species of Spongillicke 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 Ge.mmule. — 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 the Spongillid 

 gemmule. 



