SPONGES. 223 



largest specimen is about 75 millims. in length by 42 millims. in greatest breadth ; 

 another is about 140 millims. long, with a maximum diameter of 25 milliins. 



The skeleton (Plate XVI., fig. I) is an extremely irregular network of highly 

 arenaceous fibres. There is no distinct differentiation into main and secondary fibres, 

 but the reticulation is much closer along tracts which run vertically to the surface 

 and end in the surface conuli. These denser parts of the reticulation are evidently 

 homologous with the trellis-like main fibres of other Hircinise. Between them large 

 tracts may remain entirely devoid of skeleton. The fibres themselves vary a good 

 deal in thickness and in the amount of foreign matter which they contain. Usually 

 there is a very large proportion of sand or sponge spicules, and comparatively little 

 spongin ; occasionally, however, I have seen fibres without foreign inclusions. The 

 spongin of the fibres is very distinctly lamellated. 



The flagellate chambers are approximately spherical, up to about 0'04 millim. in 

 diameter (but often smaller), and either eurypylous or with short exhalant canals. 

 The ground-substance between them is finely granular, though perhaps somewhat less 

 markedly so than in typical Spongiidae. The larger canals are surrounded by a very 

 large quantity of gelatinous, vesicular-looking collenchyma, and commonly more or 

 less sub-divided by septa. Bands of fibrous tissue penetrate the soft tissues as in 

 other Spongiidae, but I have not found any of the " filaments " so common in the 

 genus Hircinia. 11. N. 13 contains an immense number of unicellular bodies of a pale 

 yellow colour (staining brown with picro- carmine) ; these are oval or nearly spherical, 

 and about 0'02 millim. in diameter ; each with a small nucleus. Occasionally they 

 appear to be broken up into fragments. Probably they are unicellular Algae, 

 comparable to those which I have described in Hexadella. R.N. 82 and 171 contain 

 numerous groups of smaller cells which are, perhaps, the same Alga in process of 

 division. 



This species exhibits characters intermediate between those of the Spongeliidse and 

 those of the Spongiidse. The skeleton, in its highly arenaceous character, agrees with 

 that of Spongelia, but the small size of the flagellate chambers and the granular 

 character of the ground-substance prevent us from including it in that genus. 

 The absence of filaments, on the other hand, militates against our regarding the 

 species as a typical Hircinia, but the nature of these filaments and their taxonomic 

 value are still so obscure that I am not inclined to exclude the sponge from the genus 

 solely on account of their absence. 



In external appearance the species somewhat resembles Cacospongia scalaris. 



R.N. 13 and 91 (Gulf of Manaar) ; 82 and 171 (deep water off Galle and onwards). 



Aplysina, NARDO. 



Spongiidaa with distinctly pithed horny fibres forming a coarse-meshed skeleton 

 network. Of very compact texture, with narrow canals and very small flagellate 

 chambers. 



