72 T. IJIMA : HEXACTINELLIDA. I. 



found, but more frequently in small than in old specimens, short 

 and young anchoring needles in various stages of development. 

 The anchor-heads attain full size in this position and are sub- 

 sequently, along with continued elongation of the shaft, pushed 

 on downwards, finally to penetrate into the substratum. 



The parenchymalia which support the loose tissue covering 

 up the skeletal latticework, are again chiefly thetactins with short 

 unilateral rays ; but not uncommonly they are also hexactins, 

 usually with one axis which to a greater or less degree is more 

 elongated than the others ; and occasionally they are diactins, 

 generally with knob-like indications of suppressed rays at the 

 spicular center. Besides these, there may occur, though ex- 

 ceptionally, any other form of spicules. All are small to medium- 

 sized spicules, ^'ji-l mm. in length and with rays 15-30/^ thick 

 near the center. The ends of the rays are sparingly beset with 

 spinules and usually terminate in a conical point. These puren- 

 chymalia frequently combine into loose, ill-defined strands, which 

 mostly extend peripherad ; otherwise, they stand isolated either 

 without any order of arrangement or with one axis pointing 

 towards the surface. 



Among the diactin-parenchynialia, those that are exlernally 

 protruded as jyrostalia at the edge of the cuff and of certain 

 parietal lappets, require special mention. AVe have here to do 

 with slender oxydiactins of very variable size — up to 5 mm. in 

 length and 20/^ in breadth — in which the center is indicated by 

 a slight annular swelling. In the positions indicated, such oxy- 

 diactins are usually numerously pre-ent and disposed in radial 

 arrangement. Some lie still completely imbedded in the body- 

 wall ; others are partially or completely projected out of the 



