REPORT ON THE MONAXONIDA. XXXV 



the sponge is very peculiar and wUl be best understood by reference to the annexed 

 woodcut (Fig. X.) (see also the description on p. 95, and figs. 9, 9o on PI. XX.). 

 Embedded in the soft tissues all round the upper margin of the 

 sponge are found, arranged in a single circle, a large number of 

 small, yellow, globular bodies (woodcut Fig. X., a, and 

 PL XLIX. fig. 4, g.h.\ What these bodies may be is an ex- 

 tremely difficult question to decide. That they are proper to the 

 species and not foreign objects or parasites is rendered almost 

 certain by the fact that they occur in the same position in all 

 three of the specimens present ; and this view of the case is ^'t^^^'t^^^^.t't^. 

 further strengthened by their histological structure, which we thr™o°nge \ »" giobuia^ToS of 



1 IT iiiiii/" 1-T,-, • unknown function, x 2. 



have worked out to the best oi our ability in two specimens. 



Unfortunately the sponges are in a very bad state of preservation, but the following 



details of structure are C[uite certain. 



In radial vertical sections through the margin of the sponge (PI. XLIX. fig. 4), we 

 find that each globular body consists of a central, more deeply staining and granular 

 portion (PL XLIX. fig. 4, (/.&.), surrounded by and embedded in a matrix of faintly staining, 

 perfectly hyaline ground substance (PL XLIX. fig. 4, s). The central portion is sharply 

 marked off from the matrix in which it lies by a much more darkly staining ring, or 

 several concentric rings of a similar substance. Within this ring we find a clear, 

 jelly-like ground substance containing very numerous embedded cells, which give 

 to the central part of the structure the granular appearance already mentioned. 

 The cells themselves (PL XLIX. fig. 4a, c) are irregular in shape, nucleated and 

 highly granular, averaging about 0"018 mm. in diameter. Outside the darkly staining 

 ring we find a very similar hyaline ground substance, but less deeply staining than the 

 inner portion and without the cells. Towards the centre of the sponge this ground 

 substance becomes gradually vacuolated and finally merges into the network of 

 tissue constituting the choanosome (PL XLIX. fig. 4, c/i.). Above, and towards the 

 periphery of the sponge, it appears to extend almost or quite to the dermal membrane, 

 becoming, however, considerably vacuolated (? owing to the action of the spirit). In 

 these parts also, but chiefly towards the periphery of the sponge, there occur, embedded 

 in the gelatinous-looking matrix, a great number of very peculiar, cup-shaped organs 

 (PL XLIX. fig. 4, gl., and fig. 46). Each of these is about 0*1 mm. in diameter, and consists 

 of a large number of small (■? spherical), deeply staining cells packed close together so as 

 to form a thick-walled cup, the mouth of which is turned towards the centre of the 

 globular body. Judging from the number to be seen in a single thin section there must 

 be a very great many of these organs present to each of the globular bodies. Around 

 them the hyaline matrix is frequently shrunk away from their walls (probably owing to 

 the action of the spirit), but usually remains connected at the mouth. The gelatinous 



