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Show 220 MR. R. KIRKPATRICK ON THE PORIFERA [Mar. 6, the size of the large nodulated type specimen obtained by Mr. J. E. S. Moore from deeper water in the same lake. The colour varies: in the case of one specimen (No. 173), preserved in formalin, it is bright green. Dr. Cunnington gives yellowish grey as the colour of another ; the rest are pale buff. The surface appears very finely granulated to the naked eye. Under magnification this appearance is seen to be due to the little projecting tufts of the main columns of spicules, each tuft-about •160 m m . in height-being formed of 2-5 spicules slightly curved away from each other ; in the nearly related Spongilla tanganyikce Evans the tufts are only 1-3 spicules thick, and the spicules are not separated at the distal end. Skeleton.-There is some variation in the size of the megascleres. In several of the specimens they average about 160 x 9 JJL, but in No. 142 they are more slender, being 150 X 6 p. A n interesting feature which is found in this and in two other species, Spongilla tanganyikce and S. cunningtoni, sp. n., from Tanganyika, lies in the presence of a basal lamella of spongin from which spongin-fibres arise (Plate X V . figs. 6, 7). In a small specimen (No. 593) preserved in picric acid, the spongin-lamella is especially well shown and the bases of the fibres can be seen through the lamella as dark round spots just visible to the naked eye. The spongin-lamella occurs also in another specimen taken from the smooth inner surface of broken Gasteropod shells (Neothauma tanganyicensis), where there could be no question of the presence of the horny layer found on the outer surface of freshwater shells. In the case of Spongilla cunningtoni, the specimen, which likewise has a basal spongin-lamella, was detached from a stone. Plate X V . fig. 7 shows spongin-fibres enclosing a core of spicules. At a short distance from the basal lamella the skeleton-fibres have only a thin, barely visible, sheath of spongin. In Euspongilla lacustris also the basal skeletal fibres are ensheathed in spongin, which diminishes from the base upwards. This condition also is found in the Chalinida?. In the marine Sponge Chalina oculata, for instance, the base of specimens is very rich in spongin, but near the summits of the branches scarcely any of this substance is j^erceptible, so that sections from the base and summit respectively might almost seem to anyone ignorant of their origin to belong to specimens of different species. In addition to the fibres, there are masses or blobs of spongin enclosing granular matter : one of these (780 x 390 /u) is shown in Plate X V . fig. 8. The gemmules occur plentifully at the base of the crust in several of the specimens. They are oval and with a very thin naked chitinous coat, through which the large polygonal statocytes can be seen. On no part of the surface is there any special opening or area through which the contents escape. Localities.-Lake Tanganyika. No. 113 from rocks, shallow water, Mbete, 29/9/04 ; No. 142, from rocks, shallow water, |