18 Journal of the Asiatic Society of Bengal. [January, liiO^. 



enlarged at the distant extremity and projects outwards tkrougli 

 the air-cells ; each group bears a single external layer of gem- 

 mule spicules, whicli lie along its suirface ; each gemmule has a 

 denser layer of similar spicules immediately outside its chitinous 

 coat, to which they are parallel or tangential ; subsidiary 

 apertures sometimes occur. 



Var. hiyemmulata. 



form : its sui 



more or less ridged; colour dull green. Skeleton containing less 

 spongin although very firm. Gemmules arranged both in errant 



base 



than in 



support, Gemmule spicules generally more slender 

 typical form ; those in the errant gemmule groups slightlj 

 slender (in the variety) than those on the pavement layer, 



r 



Average diameter of the gemmule *... 0*28 mm. 



5* 



length of the skeletx)n spicule 0*3 



(Typical formV average length of the 



gemmule spicule „. ,.. 0'1275 „ 



(Var. higeTnmuUittf) average length of 



the gemmule spicule (fixed gemmule) O'l 



(Var. hiijemmuhita) average length of 



the gemmule spicule (errant) ... 0'105 



17 



71 



Fig, 3. S'pongilla crassissiina^ 

 Node of skeleton, ebowing spongin web. 



r 



Hemarks. 



The skeleton in these Sponges is constructed of stout fascia? of 

 spicules very firmly bound together by spongin, which also occuis 

 m the form of extensive, sometimes perforate webs at the nodes 

 of the skeleton and occasionnlly as delicate filaments between the 

 fasciae I'he fascia are arranged in a close reticulation somewhat 

 irregular as regards its meshes, which are crossed diagonally by 

 fiingk spicules and fascige composed of two or three spicules. 

 J he inesh-work surrounds the canals, which radiate outwards 

 trom the fiupport of the Sponge and are relatively narrow 



