96 i. ijima : hexactinellida. t. 



Spiculation. 



E. Marshalli is one of those species whose spicules remain 

 all perfectly free, never and nowhere becoming soldered together 

 by synapticula?. I am inclined to bring this in correlation with the 

 fact that no point of the living parts is in direct contact with 

 the substratum (see p. 45). 



The composition of the ^9a?'e«c7i^?/w?«/i« is essentially the same 

 as that which I have described for E. imperialis. The large or 

 medium-sized stauractin principalla, common to the transverse 

 and the longitudinal beams of the skeletal framework, have 

 slender tapering rays which are subterminally roughened and 

 generally conically pointed at the ends. The rays may be 110/^ 

 thick near the spiciilar center, the longitudinal axis being 4o mm. 

 or more and the transverse 20 mm. in length. The two rays 

 constituting the former axis are usually of unequal length but 

 form a straight line, w^hile those of the latter are symmetrical 

 in length and form with each other an obtuse angle open towards 

 the axis of the body, or are at any rate bent to conform with 

 the curvature of the circumference. Toward either end of the 

 sponge, the stauractins become smaller, the rays at the same time 

 approximating in their relative length. 



The comitalia to the above principalia are, as usual, mostly 

 thetactins ; occasionally also hexactins, paratetractins or pentactins, 

 and rarely diactins. In all these, the rays in an axis, which 

 runs along with the principnlia, are greatly prolonged (up to 

 2 mm. or more in axial length) in excess over the remaining 

 ray or rays -which spring out more or less vertically from the 

 beams. The diactin comitalia have the center marked by an 



