220 MR. R. KIUKrAT)?IC'K OX THE PORIFERA [Mar. G, 



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. 1 73), preserved 

 in formalin, it is bidght green. Dr. Cunning-fcon gives yellowish 

 grey as the colour of another ; the I'est are pale bufl;'. 



The svn-face 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 mm, in height — being formed of 2-5 spicules slightly curved 

 away fi'om each other ; in the nearly related Sjjovgilla tanganyikcti 

 Evans the tufts ai'e on! 3^ 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 sevei^al of the specimens they average about 160 x 9 ^, but in 

 No. 142 they are more slender, being 150 x 6 /.«. 



An interesting featui'e which is found in this and in two other 

 species, Spongilla tanganyikce and S. cunningtoni, sp. n., from Tan- 

 ganyika, lies in the presence of a basal lamella of spongin from 

 which spongin-fibres arise (Plate XV. 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 {N'eothauma tanganyicensis), where there could be no question 

 of the presence of the horny layer found on the outer surface of 

 fi-eshwater shells. In the case of Spongilla cunningtoni, the 

 specimen, which likewise has a basal spongin-lamella, was detached 

 from a. stone. 



Plate XV. 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 

 Evjspongilla lacustris also the basal skeletal fibres are ensheathed 

 in spongin, which diminishes from the base upwai-ds. This con- 

 dition also is found in the Chalinida;. In the marine Sponge 

 Chalina ocidata, for instance, the base of specimens is veiy rich 

 in spongin, but near the summits of the branches scarcely any of 

 this substance is perceptible, so that sections from the base and 

 summit respectively miglit 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 p) is shown 

 in Plate XY. fig. 8. 



The gemmules occur plentifully at the base of the crust in 

 several of the specimens. They ai'e oval and with a very thin 

 naked chitinous coat, thi-ough which the large polygonal statocytes 

 can be seen. On no pai^t of the sui-face 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. 



