The Tanganyika problem; an account of the researches undertaken concerning the existence of marine animals in Central Africa . they are so frequent that they must be considered as a normal feature ofthe species. It is possible that in other Spongillidre these systems have not receivedthe attention they deserve. In addition to the spicules described above there are small masses of silica inSpongilla moorei, comparable with those found in Spongilla aspinosa (Fig. 1—e.). (B) The Arrangement of the Spicules to form Fibres, etc.—The spiculeswhich form the polyspiculous fibres belong mainly to the f
The Tanganyika problem; an account of the researches undertaken concerning the existence of marine animals in Central Africa . they are so frequent that they must be considered as a normal feature ofthe species. It is possible that in other Spongillidre these systems have not receivedthe attention they deserve. In addition to the spicules described above there are small masses of silica inSpongilla moorei, comparable with those found in Spongilla aspinosa (Fig. 1—e.). (B) The Arrangement of the Spicules to form Fibres, etc.—The spiculeswhich form the polyspiculous fibres belong mainly to the first and third classesabove described. Spicules of the first class form the greater part of the fibres, whileothers lie about in the sponge tissue, presenting for the most part an iiregularmethod of arrangement, though many such spicules are placed so as to bridge overthe spaces between the fibres in a perfectly definite way. Spicules of the secondclass, which are far less numerous than those of the first, seldom participate in theformation of the fibres, but, as a rule, lie scattered irregularly between the ?j> -,y %, /.-^^ Fig. 2.—a., The skeleton of Spongilla mooreineax the surface in section X 200. />., Aportion of two fibres X 800. c., The skeleton as seen in section from the base to theupper surface. 314 THE TANGANYIKA PROBLEM. The spicular systems of the third class are seldom found in any other position thanin the fibres. As a rule, the spicules are arranged in the fibres with their axes parallel to oneanother, and in the deeper parts of the sponge the connecting spicules are rathernumerous, and more strongly developed than in the more superficial parts. Theconnecting spicules are usually the most strongly developed spicules in the wholesponge as regards size, differing, however, only in thickness from the smooth, curvedamphitornota which constitute the fibres (Fig. 2—a.). Speaking generally, the largestspicules of the first class,
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