18 ART. 1. — I. IJIMA : HEXACTINELLTDA, III. 



Finally, as to the spiculation of the stalk and of the 

 basal disc. 



In both these parts the main mass of the parenchyme is 

 rigid and consists of long, synapticularly connected diactins, 

 measuring 10-40/^ in thickness. These run in longitudinal bundles 

 in the stalk, while in the disc they are disposed more or less 

 parallel to the surface but otherwise in nil directions. Hexasters 

 among the fused parenchymalia seem to be rarely present. 



Towards the external surface, in both the stalk and the 

 disc, the synapticulœ cease to exist. The peripheral diactinic 

 jiarenchymalia thus left loose and unconnected, together with 

 the dermalia and the hexasters present, form a soft tissue which 

 in a thin layer covers the entire external surface of the parts 

 in question, besides constituting the substance of the thin oscula- 

 bearing sheet which partially shuts off the large excurrent canals 

 from the exterior (see p. 9). 



The dermalia of the stalk compare well with those of the 

 body, except in often having the distal ray considerably reduced 

 in length, sometimes even to a mere knob or a gentle swelling. 

 And, lower down the sponge, i.e., on the disc-surface, this ray is 

 completely lost in all, so that here the dermalia are pentactinic, 

 — a condition which may possibly represent the state as assumably 

 obtains in the entire dermal layer of the species in the earliest 

 period of postlarval development, as I have found to be the case 

 in young RegadreUa oJcinoseana (see Contrib. I., pp. 246, 247). 

 In all the dermalia the proximal ray, j^enetrating into the 

 underlying tissue, is always the longest. Seen on the surface, 

 the paratangential crosses lie rather densely crowded, without any 

 regularity as to their relative position. 



The hexasters in the said soft tissue of the ]ieriphery are 



