CALYCOSILVA CANTHARELLUS. • 71 



central part of the gastral face of the sponge are observed where the stalk is 

 attached to the body proper. 



Some canals are traversed by thread-like or membraneous trabeculae, others 

 appear to be destitute of such. It is difficult to say whether the latter are empty 

 in the living sponge, or whether they have lost their trabeculae after capture. 

 I think, liowever, that the latter assumption is more likely to be correct than the 

 former. 



The trabeculae traversing the cavity of the stalk are distinctly membrane- 

 ous, and stouter and more distant than the ones spread out in the canals of the 

 body proper of the sponge. 



The flagellate chambers (Plate 2, fig. 7a) form a continuous layer interA^en- 

 ing between the afferent and efferent canals. They are more or less oval, wide- 

 movithed sacs and measure 70-100 ii in transverse diameter. Their length varies 

 considerably, from 120 to 220 /x. 



More or less spherical bodies 2-5 m in diameter are met in various parts of 

 the sponge. These lie either singly or in groups, and stain strongly with aniline- 

 blue and magenta. The largest of the groups formed by them attain a maxi- 

 mum diameter of 36 yu, and are composed of forty or more such bodies. Some of 

 them, particularly the larger single ones, are enclosed in spherical envelopes, 

 about 9 Ai in diameter, which are often very distinct and appear as cell-walls. 

 The space between the highly stained body and the envelope is occupied by a 

 colourless (unstained) and transparent substance. The highly stained body is 

 not always stained uniformly throughout. One can often distinguish within it 

 a not so strongly stained ground-substance, and a very strongly stained, irregu- 

 larly branched, apparently chromidial mass. On a few of the envelopes enclos- 

 ing these bodies was observed a circle, 2 n in diameter; this appeared as the 

 margin of a round aperture, perhaps covered by an operculum. In one of 

 these the stained body did not lie altogether within the envelope but had partly 

 emerged from it through this aperture and filled it up like a phig. 



The spicules taking part in the formation of the skeleton are: — large, stout- 

 rayed hexactines; derivates of these hexactines with less than six rays, mostly 

 diactines (in C. c. var. swwpfex only) ; ordinary rhabds; slender, rectangulai'ly 

 bent diactines (in C. c. \a,Y. helix only); large, slender-rayed triactines (in 

 C. c. var. megomjchia only) ; pentactines ; hexactine pinules with a fully developed 

 or a reduced proximal ray; a few microhexactines (in C. c. vars. simplex and helix 

 only) ; a series of forms of regular onychhexasters ; a few irregular onychhexasters ; 

 onychhexaster-derivate oxyhexasters (in C. c. vars. helix and megonychia only) ; 



