434 



REVISION OF THE MONAXONID SPONGES, 111. 



varying stoutness; the latter are composed of roughly parallel 

 spicules cemented by spongin, which usually forms a distinct 

 sheath, but sometimes is barely more than sufficient in quantity 

 to hold the spicules together. The primary fibres attain a 

 diameter ranging in different specimens from about 80 to 130/x, 

 while the slenderest of the connecting fibres are but two or three 

 spicules broad; single connecting spicules also occur. In the 

 meshes of the reticulation, megascleres are scattered in some 

 abundance, together with a few raphides; in the canal-traversed 

 soft tissues occupying the wider interstices of the skeleton, on 



A 



Fig.20. — Hemitedania anonyma. a,Oxea, from each of three different 

 specimens. 6,0nychet£e. 



the Other hand, it is the raphides which are the more numerous. 

 In addition to the fibres which compose the reticulation, separate 

 strands of loosely associated parallel spicules, free from spongin, 

 occur, sometimes consisting of oxea alone, more frequently of 

 oxea and raphides in variable proportion, and apparently some- 

 times of raphides alone. The raphides also occur in dragmata, 

 but these are sometimes extremely scarce. The dermal skeleton 

 consists of vertical lufts of megascleres projecting slightly beyond 

 the surface, and usually so disposed in linear series as to produce 



