252 ART. 7.— I. IJIMA : HEXACTINELLIDA, IV. 



Onseveral occasions I have distinctly observed the presence 

 of a film-like memhrana reuniens (Contrib. I., p. 130) filling up 

 the gap between the circular apopyles of three or four, directly 

 adjoining chambers (fig. 20, /.), thus shutting off at the spot 

 the iutercameral incurrent space from the excurrent lacunse of 

 the internal trabecular layer. At other times, however, the gaps 

 were clearly seen to be open (fig. 20, g.), so that I believe the 

 membrana reuniens is not a thing of constant occurrence. 



Dermal and gastral membranes, rather extensively film-like 

 (PL XVIII., fig. 16). Trabeculœ, thread-like ; rather sparse in 

 the subdermal space as well as along the lumen of both incurrent 

 and excurrent canals. Their nuclei, at most 2 ,« in diameter ; 

 scattered at irregular intervals. 



Archœocytes, found in small flat groups on the wall of 

 chambers ; not forming large congeries, which fact is probably 

 due to the immature state of the specimen. 



Scattered in irregular distribution and suspended on the 

 trabeculœ, both external and internal, are found numerous fat- 

 like spheres of various sizes (shown in figs. 20-22 as black dots). 

 Diameter, 72-20/^. Sometimes they seem to be inclosed in a 

 thin envelope ; more often they are apparently quite naked. Their 

 substance is either homogeneous or granular ; it is intensely 

 stained by carmine or hsematoxylin, and is browned by osmic- 

 acid but is not coloured blue by iodine. Neither alcohol nor 

 ether dissolves it. I have therefore no doubt as to the bodies 

 being thesocytal products. Frequently two spheres are seen closely 

 apposed to each other, as if they had taken origin and were 

 actually lying together within one and the same cell, — which is 

 probably the real fact, though the nucleus can not be distin- 

 o'uished. 



