184 HIRCINIA. 



Hircinia gigantea, Eidley. 



Cacospongia irregularis, N. de Polejaeff , Report on the Scientific Eesults of the 

 Voyage of H.M.S. ' Challenger,' Zoology, vol. si. Keratosa, p. 63 (1884). 



Hircinia liorrens, S. O. Ridley, " Spongiida " : Report on the Zoological Col- 

 lections made in the Indo-Pacific Ocean during the Voyage of H.M.S. 

 ' Alert,' p. 387 (1884). 



Massive, globose, more or less regularly spherical sponges, which are attached 

 by a broad base and attain a very large size. Most of the specimens have a 

 diameter of about 300 millim., but I have seen one which measured nearly 

 half a metre across and weighed about a hundredweight. The surface is 

 covered with blunt and irregular, often truncate conuli, about 4 raillim. high, 

 which are on an average 8 millim. apart. The oscula are circular, 15 millim. 

 wide, and confined to the upper side of the sponge. Besides these, a few other 

 holes, 5-15 millim. wide, are found in the surface, leading down into extensive 

 lacunae 10-15 millim. wide, which pervade the whole of the sponge. These 

 are so numerous that septa only 5-15 millim. thick are left between them. 

 They are inhabited by great numbers of small Decapods. The living sponge 

 is pretty soft and compressible ; large specimens partly collapse when taken 

 from the water. The dry skeleton is stiff and elastic. The colour of the living 

 sponge is dull orange-red on the surface, and lighter in the interior. The 

 upper surface is more intensely coloured than the lower. 



The skeleton consists of longitudinal, irregular, cylindrical, dense fascicles 

 1-1-5 miUim. thick, 1-3 millim. apart, and connected at intervals of 3 millim. 

 by transverse fascicles, which taper from both trumpet-shaped extended ends 

 to the centre, where they are only about 0-4 miUim. thick. The trumpet- 

 shaped basal extensions are nearly 1 millim. wide. The fascicles are composed 

 of fibres 0-04 millim. thick, which are about 0*02 millim. apart and frequently 

 fused or joined by short and stout transverse fibres. Towards the surface 

 of the fascicle the fibres are closer together than in the interior : here two 

 or three are often fused for a considerable length. The filaments are arranged 

 in very remarkable band-shaped bundles, about 0*06 millim. thick, which extend 

 principally longitudinally in the walls of the small canals. The filaments are 

 0-0015 millim. thick, and covered with brown spots ; their terminal knots are 

 oval, 0-0025 millim. broad. 



The inhalant pores are 0-02 millim. wdde, and lead into very short canals 

 which penetrate the thin skin. No foreign bodies, or only very few, are con- 

 tained in the latter. Below it subdermal canals, 0'3-0-7 millim. wdde, extend, 

 from which the inhalant canal-stems, 0-2-0-4 millim. wide, originate. The 

 branches of the inhalant system are very wide, measuring on an average 0-1-0-2 



