Species of Don.at i a (Tethya). 17 



of variety A. It is prune-coloured, varying from purple to 

 brown. In alcohol it is dull light brown with a pinkish cast. 

 It shows less extremes of size than variety A, and has never 

 been found with strongly developed anchoring filaments. 

 The oscula, though of the same general character, are 

 pronounced, and in most cases their plates do not project 

 conspicuously. The specimens which in the field are distin- 

 guished from variety A by these superficial characters, present 

 upon study of their internal structure two points of difference 

 from the more common green form : — (1) The cortex of 

 variety A consists of a thin fibrous inner layer and a thick 

 fleshy outer layer, while that of variety B, of equally con- 

 spicuous total thickness, is composed of a very thick fibrous 

 inner cortex and a thin outer layer of fleshy material. Upon 

 this point variety 13 agrees with the description given by 

 Sollas of the cortex of I>. ingalli, but both varieties have the 

 great total cortex thickness mentioned by Dendy as charac- 

 terizing the specimens of 1). ingalli examined by him. 

 (2) The cortex of variety 15 is densely packed with spherasters, 

 a feature which agrees with the condition found by Dendy ; 

 while the cortical spherasters of variety A, though un- 

 doubtedly more numerous than in D. seydiellensis, are far 

 from being densely packed. 



III. Donatia lyncurium (auctorum). 



Donatio, lyncurium has apparently not passed through its 

 season of greatest abundance and activity during the period 

 covered by my observations. I have never found a single 

 specimen in the eel-grass of the tidal creeks, and search in 

 other localities has revealed only a few small animals without 

 buds. These were attached to stones at low-water mark 

 along the shore of Agar's Island. Their colour varies from 

 light yellow to orange, the smaller ones being usually of the 

 lighter hue. They range in diameter from 5 to 20 mm. 

 None have been found attached to the stones by anchoring 

 3, but the base is flattened, so that the centre of the 

 radiating structures is not far above the region of attachment. 

 The surface is covered with fine rounded elevations, which in 

 a few of the larger specimens are modified into elongated 

 plates about the osculum. A specimen of 20 mm. maximum 

 diameter has a cortex 2 mm. thick, which consists of a very 

 thin fibrous inner layer and a thick fleshy outer layer. The 

 choanosome is dark yellow, fading into green at the periphery. 

 There is a large fibrous core at the centre of the radiating 

 bundles. The outer fleshy layer, yellow when the sponge is 

 Ann. <& Mag. X Hist, Ser. 9. Vol. i. 2 



