62 RAPHYEUS. 



coloured pigment, very similar to that extracted by spirit from many other 

 sponges. 



The surface is reticulated throughout in a very regular and uniform manner, 

 and is very similar to the surface of Bowerbank's Raphyrus griffitlmi, and also 

 to that of some species of Halme among horny sponges. Young and old speci- 

 mens always show the same reticulation on the surface ; there seem never to 

 be papillfe in the place of the meshes, as is the case in young specimens of the 

 genus PajnlUna, 0. Schmidt. The reticulation is produced by a very regular 

 network of 2 millim. broad projecting lines. In the meshes between these 

 there are slight depressions about 4-5 millim. deep ; the regularly polygonal 

 meshes themselves have a width of 3-4 millim. ; the concave membranes which 

 are expanded in the meshes are very soft, whilst the projecting lines are exceed- 

 ingly hard ; in these membranes we find groups of small pores, which lead into 

 the inhalant canals. This network covers the whole of the surface of the 

 sponge, and extends in the conic tubes down to their bottom. Oscula are 

 found scattered irregularly over the whole of the surface ; they are circular 

 and measure from 2-10 millim. in diameter; these oscula are as frequent on 

 the exposed parts of the sponge as in the sides of the conic tubes. 



The whole sponge consists of a reticulate structure. Lamellous fibres with 

 an average thickness of 1 millim. form a network, which appears very regular 

 on every section ; these fibres consist of a very hard tissue, with few and small 

 canals and a great abundance of spicules ; in tlie meshes between them there is 

 a very much softer tissue, with wider canals or irregular lacunse ; here, only 

 few and insignificant spicules are observed. Below the pore-sieves, in the 

 concave membranes which extend in the meshes of the surface-network, large 

 irregular cavities are met wath. The pores are situated, as stated above, in small 

 groups ; the sieve-membranes are very thin and delicate. The pores can appa- 

 rently be entirely closed by the sponge. The subdermal cavity extends far 

 down and gives off branches, which ramify to supply the ciliated chambers or 

 extend to form lacunse in other parts of the interior of the sponge ; most of 

 the lacunffi found throughout the interior of the sponge belong to the inhalant 

 system. The ciliated chambers are small and difficult to see ; they are 

 spherical and measure 0'02 millim. in diameter; from the chambers very 

 narrow canals originate, which unite to form the larger exhalants. The 

 chambers are situated in groups, which occur both in the tissue of the hard 

 fibres, and also in the soft pulpa which occupies the cells of the honeycomb- 

 like structure. The exhalant canals do not form extensive lacunse ; the larger 

 branches and stems are found only in the soft tissue of the meshes ; the oscular 

 tubes follow the network in their lower part, and are therefore much curved ; 

 they are narrow, long, and ramified in an irregular manner. 



Skeleton. — The skeleton consists of the tylostyli and styli described by 

 Bowerbauk and O. Schmidt in their genera liaplvjrus and Papillina, to 



