SPONGES. Ill 



which the Tethyidse may have originated, through the Epipolasidae, from stellettid 



ancestors. 



Cryptotethya agglutinans, n. sp. Plate V., figs. 4, 5. 



The single specimen (Plate V., fig. 4) consists of a more or less spherical body from 

 which radiate irregular finger-like processes of varying shape, long or short, 

 cylindrical or flattened, and sometimes expanded at the free end. Between these 

 projections the surface of the sponge is for the most part concealed by a great quantity 

 of calcareous debris which firmly adheres to the sponge, including melobesian nodules 

 of considerable size, worm-tubes, Foraminifera, &c., the whole forming an irregular 

 mass in the midst of which the body of the sponge is scarcely recognisable. Calcareous 

 debris may also be found in the interior of the sponge, even within the choanosome. 

 I have not succeeded in making out the arrangement of the vents and pores. Some 

 small openings on the ends of some of the projections resemble vents, but on close 

 examination are found to be merely the apertures of cavities inhabited by parasitic 

 barnacles. One at least of the shorter projections (fig. 4, x), however, contains 

 longitudinal canals which are evidently either inhalant or exhalant canals proper to 

 the sponge. The surface of the sponge, where exposed, is very uneven and very 

 harsh to the touch, owing to the projection of the large oxea, which readily break oft' 

 in one's skin and thus make the sponge very unpleasant to handle. The colour of 

 the surface and of the thick outer layer of the ectosome (in spirit) is grey, of the thin 

 fibrous layer of the ectosome white, and of the choanosome nearly white. The 

 maximum diameter of the body of the sponge is about 40 millims., the length of the 

 longest projection about 25 millims. 



In the body of the sponge the huge oxea of which the skeleton is composed are for 

 the most part arranged radially and without any distinction between choanosome and 

 ectosome, passing indifferently from one to the other through the dense fibrous layer. 

 Some of the oxea are associated in loose bands which spread out in brushes as they 

 approach the surface. In the projections the oxea naturally lie for the most part 

 longitudinally, but at the expanded end of a broad projection (containing longitudinal 

 canals) I have found a good many placed tangentially at or near the surface. The 

 asters are for the most part arranged, (very abundantly) in a thin dermal layer, 

 through which the points of the oxea may project for a short distance. 



Spicules. (1.) Oxea (Plate V., fig. 5, a, b) ; stout, fusiform, usually gradually and 

 fairly sharply pointed, but subject to some irregularity at the ends and occasionally 

 stylote. Size very variable, say about 2'5 millims. by 0'073 millim. when fully 

 grown, but often less. 



(2.) Chiasters (Plate V., fig. 5, c), with little or no centrum and smooth, slender, 

 sub-cylindrical rays, ending bluntly, but not tylote ; total diameter commonly about 

 0'012 millim. These spicules are most abundant at or near the surface of the sponge, 

 but a few precisely similar forms occur in the choanosome. 



