106 ART. 7. — I. IJIMA : HEXACTINELLTDA, IV. 



tioned, a continuous autogastral layer covering np the meshes of 

 the hypogastral framework seems not to exist. Perhaps worth 

 noting is the fact that the paratangentials are frequently observed 

 running among or under, instead of over, the diactinic elements 

 of the hypogastral beams. 



Hexactins similar to the gastralia occur in some number as 

 canalaria on the l)eams of the lattice-like layer lining the lumen 

 of the larger excurrent canals. 



Of the hexasters, oxyhexasters (PL VIIT., figs. 12-16) occur 

 in abundance in the choanosome. Diameter or axial length, 80- 

 125 //. They are mostly hexactinose and less frequently herai- 

 hexactinose. In the latter case, one to three of the six, extremely 

 short or nearly entirely atrophied principals bear each two widely 

 diverging terminals. In fact, three seems to be the utmost num- 

 ber of principals that may be biterminal in an oxyhexaster. At 

 any rate, normally developed oxyhexasters, i. e., those in wdiich 

 all the six principals bear more than one terminal each, were on 

 no occasion met with. The uniterminal rays, i. e., those consist- 

 ing of a principal continued into a single terminal, w^hether be- 

 longing to a hexactinose or to a hemihexactinose oxyhexaster, 

 are either bent at base or are straight or nearly straight from 

 the origin at the central node. PL VIII., fig. 16, represents a 

 rare case of a hemihexactinose oxyhexaster w^ith peculiarly bent 

 rays. Now^ and then there are observed cases of a principal 

 bearing a terminal of normal length and in addition the short 

 rudiment of a second. PL VIII., fig. 14, is an example of such 

 cases ; and text-figure 5, on p. 100, may well pass for one taken 

 from the present sj^ecies. Occasionally a principal together with 

 its terminal seems to be totally suppressed in development ; only 



