206 ART. 7. 1. IJIMA : HEXACTINELLDIA, IV. 



The central node \a provided with the six tabercles which are 

 moderately [)roiiniieiit, I'hc necondary principal measures in length 

 between h and i that of the entire ray. 'J'lie number of terminals 

 to each principal may be |)ut down at 5-10, but is more usually 

 8-10. The terminals appear to be rather strong ; at any rate 

 they cannot exactly be called fine. The tuft they form is about 

 10 fji broad at base and may expand to thrice that breadth at 

 the outer end. Each terminal gently bends slightly outwards in 

 its course towards the thinly attenuated en(], which is furnished 

 with a pinhead-like terminal disc. 



The microdiscoJicxaslcrs (PI. VII I., iig. 22) seem to be very 

 sparse ; in fact they were met with only in a few isolated cases, 

 in what })art of the wall I can not definitely state'. Diameter 

 23-2(3 /^. The terminals are exceedingly fine and not very numer- 

 ous. They give a spherical shape to the entire spicule. The 

 })rincipals may be simply knob-like as shown in the figure ; but 

 this is not always the case ; for, in some specimens of the spicule 

 I have seen each shoi't principal furni«lied with the usual ter- 

 minals-bearing discs at their outer ends. 



Finally, the hciiiidiGlijomd i)hite. This I have isolated in 

 small fragments from the attachment surface. In these I have 

 made out that the single spicules, which by amalgamation go to 

 constitute the plate, are mainly stout stauractins and occasionally 

 pentactins. The rays in these spicules may be as thick as lo /^, 

 their surface showing microtubercles in moderate numbers. The 

 fact that these spicules are not hexactins as is the rule with dic- 

 tyobasalia in general, probabl}^ has some connexion with the 

 thinness of the plate in the present case. 



