14 



A root-tuft or peduncle, 6 mm. in diameter, and composed of spirally inter- 

 twined spicules, each about 500 /* thick, protrudes from the basal, attenuated 

 end of the sponge-body. ' The lower end of the peduncle has been torn off, the 

 upper and central parts of it, still attached to the specimen, are together over 16 

 cm. long (pi. V, f. 1). 



It is remarkable that the Palythoa-crust covering the upper dense part of 

 the peduncle in many other Hyalonemas, is here replaced by Cirripedes. From 10 

 cm. below the insertion of the peduncle in the sponge-body downwards, a number 

 of these sessile crustaceans of varying size, some as much as 44 mm. long, are at- 

 tached to it. They stand pretty close together but do not form a continuous 

 covering. Dr. Weltner of the Berlin Museum fiir Naturkunde, who was so good 

 as to examine them at my request, found that most of them belong to a new 

 species of the genus Scalpellum hitherto not recorded from the Indian Ocean. 

 He described them as Scalpellum squamuliferum in the Sitzungsberichte der 

 Gesellschaft naturforschender Freunde zu Berlin for 1894 on p. 81. One of these 

 cirripedes, which is 8 mm. long, represents a different species. This he named 

 (I.e.) Megalasma carino-dentatum. 



Below, where the peduncle has been torn off, the spicules diverge. 

 The sponge is rather stiff and also the marginal part of the funnel-wall fairly 

 resistant. The interior is clay-coloured, the surface has a rust-red tinge. It is 

 difficult to say whether one is to consider this superficial tint, which is divided 

 from the parenchymal clay-colour by a well defined limit, as proper to the sponge 

 or as a precipitate produced in the spirit used for preserving the specimen. 



The macroscleres resemble in shape and position those of other Hyalonema 

 species. It must be remarked however that the diactines of the parenchyme are 

 here in H. masoni unusually prevalent. In thin sections, particularly of the mar- 

 ginal part of the funnel- wall, one only rarely finds larger oxyhexactines between 

 the numerous diactines which either terminate with sharp points or with slight, 

 rouo-h inflations. The dermal and gastral membranes and the walls of the larger 

 excurrent canals are supported, as in other Hyalonemas, by stout, smooth oxy- 

 pentactines. 



In the lower basal part of the sponge-body siliceous spheres are not infre- 

 quently met with between the medium sized acanthophores which have the usual 

 structure. These spheres are composed of regularly concentric layers of silica, so 

 that they can appropriately be termed " silica pearls." I have found and des- 

 cribed * such pearls also in Pheroncma girjanteum F. E. Sch. 



The dermal pinules are very uniformly developed on all parts of the surface. 

 They resemble in appearance Italian poplar-trees {Populus jnjymniclalis) and 

 are on an average 160 /* high. Their basal rays are stout, about 2 J m long and 



* Sitzber, der Berliner Akadeniie, 1893 p. 996. 



