HALICHONDRIA. 113 



softish and compressible, or firmer and harsh to the feel. Fe- 

 cal orifices generally obscm*e or obsolete. Spicula very nume- 

 rous, rather short, curved in a slight degree, sharp at one end 

 and obtuse and rounded at the other : they are not all of the 

 same length, and amongst those which principally compose the 

 skeleton of the sponge are mixed some which are comparatively 

 slender. The meshes are formed by the cross-layings of the 

 spicula, which occasionally are so free of horny matter that their 

 foiTii can be detected without previous incineration or macera- 

 tion in an acid. The degree of softness in the species depends 

 much on its habitat. When parasitical on Sertulariag, which 

 grow in a state of constant submersion, the texture is softer, looser 

 and finer than when it is parasitical on the littoral sea-weeds ; 

 and I have found the spicula in the former variety more unequal 

 than in the latter, the common sort being mixed up with others 

 of greater slenderness and length. The texture of the littoral 

 variety is like that of H. simulans, but more uniformly porous, 

 and there are rarely any oscula. It is occasionally of a reddish 

 colour, as are also H. palmata, oculata, and several others of 

 the genus. 



To this species undoubtedly belongs the " sponginess" men- 

 tioned by Pallas under his description of Spongia crateriformis : 

 — " Massas simillimse substantia?, quosdam subturbinatas, in- 

 foi-mes, albidioresque habeo ex mari Antlquam Insulem alluente. 

 Subsimilem quoque spongiositatem in Sussexice littore in parvis 

 massulis, aut et Fuco pinastroidi immixtam observavi.'' Elench. 

 p. 386. — And there is as little hesitation in saying that the 

 " doubtful species" mentioned by Mr Templeton (Mag. Nat. 

 Hist. ix. 471,) as " a good deal like Spongia lobata, Mont., of a 

 dark brown, and covering the stems of a piece of Fucus siliquosus," 

 can be no other than a state of H. fucorum. I have even seen 

 it in a crustaceous state, spreading on the surface of a rock, so 

 very like the primary condition of H. palmata that the distinct- 



