REPORT ON THE MONAXONIDA. 215 



it is doubtful whether or no any opening exists in the living sponge, though traces of 

 what appears to be such can be found. Colour in spirit yellowish-grey. Texture tough 

 and leathery, internally coarsely fibrous ; the cortex is very firmly adherent to the under- 

 lying tissues. Surface between and on the mammiform processes even, seen in sections 

 to be minutely hispid ; the hispidity is more strongly marked over the body than on the 

 mammiform processes ; on the body there is a considerable amount of foreign matter 

 collected, while the mammiform processes are free from it and almost glabrous in appear- 

 ance. Oscula (? minute, at the summits of the papillse). Pores scattered (? singly) 

 over the surface of the body and of the mammiform processes. 



Skeleton. — (a) Of the main body (1) a thin, very dense and compact external layer 

 (PI. XLII. fig. 6, b), about O'lS mm. thick, composed of vertically placed, tightly packed, 

 smaU, straight and slender tylostylote spicules, with their apices directed outwards and 

 projecting for a short distance beyond the surface of the sponge. (2) Immediately below 

 the above and inseparable from it a similar but very much thicker layer (PL XLII. 

 fig. 6, c) of larger, stout tylostylote spicules, arranged as in the first layer and with 

 their apices embedded in it, thickness about 0-35 mm. These two layers may be 

 considered as cortical. Besides the spicules already mentioned, there are in the 

 cortex spicules of another and very remarkable kind, the grapnel-spicules (PI. XLII. 

 fig. 6, d) to be described later. These have the base and part of the shaft embedded 

 in the cortex while the remainder of the spicule projects freely for a considerable distance 

 beyond the surface of the sponge, and bears at its extremity the grapnel. Immediately 

 below the cortex, as above defined, comes a layer (PI. XLII. fig. 6) about as thick as the 

 second cortical layer, of still larger, stout tylostylote spicules, not vertically disposed Init 

 for the most part horizontally and irregularly, forming a compact mass. Below this 

 layer comes the general parenchyma of the sponge (choanosome), with very numerous 

 scattered tylostylote spicules, and with very well defined, stout fibres (PI. XLII. fig. 6, a), 

 composed of large stylote or sul)tylostylote spicules longitudinally placed and with their 

 apices outwardly directed. These primary fibres run vertically towards the surface of 

 the sponge ; before arriving there they expand into divergent brushes of large spicules 

 whose apices penetrate right into or even through the cortex. Secondary skeleton fibres, 

 if present at aU, are very ill defined, (b) The skeleton of the mammiform jDrocesses 

 (PI. XLII. fig. 7); the cortex and the layer immediately below it are arranged very 

 much as in the main body, except with regard to the grapnel-spicules, which seem to be 

 entirely absent ; then come very definite, stout, longitudinally placed bundles of spiculo- 

 fibre (PI. XLII. fig. 7, a), like those of the main body and arranged mainly, and fairly 

 regularly, in two concentric circles, and with the spaces between them filled with a great 

 number of irregularly but closely arranged tylostylote spicules ; in the centre of the inner 

 circle of fibre bundles is a space almost quite free from spicules and filled with a yellow, 

 granular substance. 



