252 Mr. W. J. Sollas on the 



layer. The attachment of the fibres of the ligament is pro- 

 vided by the tubercles of the globate ; and when a globate is 

 torn out from the cortex it carries its ligaments with it, as a 

 hair-like coating of radiating fibres. 



The fibres are exceeding fine threads, mere lines in thick- 

 ness, and consist of altered protoplasm, which stains but very 

 slightly with carmine. Small refringent granules occur 

 amongst them ; and in places they appear to pass into the 

 fibres of the succeeding cortical layer (PL XL fig. 7,f) . This, 

 which in describing Stelletta Normani (Sollas) we called the 

 muscular layer, is comparatively thin, varying from 0*0015 to 

 0'0035 inch in thickness. It consists of fibres similar to those 

 of S. Normani, arranged in variously oriented fasciae, in a 

 layer which is closely opposed to the inferior face of the globate 

 layer ; intermingled with the fibres are a considerable number 

 of vacuolated connective-tissue cells, which are frequently 

 aggregated together in groups, and sometimes form a distinct 

 stratum on the lower face of the muscular layer, which, 

 most exteriorly, is always covered by an epithelial mem- 

 brane with associated cylindro-stellates. The trifid heads of 

 the ternate spicules which appear to support the cortex are 

 also imbedded in the muscular layer, the fusiform fibres gene- 

 rally surrounding the spicular rays concentrically. This 

 arrangement is shown on the left-hand side of the endochone 

 in fig. 7 (PI. XL). 



2. The Chones. — The ectochone of the cortical layer has 

 generally the form of an inverted bell, covered by a thin 

 dermal layer above and closed by a muscular sphincter below. 

 From its upper and outer angle canals extend themselves 

 horizontally into the dermis, and, widening out, give rise to a 

 shallow dermal cavity, the roof of which is united to the floor 

 by small columns of connective tissue. The layer of tissue 

 covering the ectochone and that above the dermal cavities are 

 perforated by a number of very short tubes or ostia, which 

 place the cavity of the chone in communication with the 

 external medium. The endochone is a shallow dome-shaped 

 cavity which communicates freely with the subcortical crypt. 

 The surface of the chone and its canals is continuously lined 

 throughout with an epithelial membrane containing numerous 

 cylindro -stellate spicules. The roof of the chone consists of 

 fine fibrous tissue lined below with the stellate-bearing epi- 

 thelium, which is continued over the sides of the ostia into the 

 layer of epidermis which covers the roof of the chone above 

 (PI. XII. fig. 33). The fibres of the chonal roof surround the 

 ostia sphinctrally. The ectochone, when it lies in the globate 

 layer, is surrounded by vesicular connective tissue, while the 



