230 ART. 7. 1. IJIMA : HEXACÏINELLDIA, IV. 



dance in the entire wall. They are slender-rayed and on the 

 whole small thongh of varions sizes. The diameter is usually 

 140-200 I'- ; occasionally, only 100 /^. The central node is either 

 plain or tubercled. The principals are about half as long as the 

 terminals. Number of termiuals to a principal, 2-4 ; usually 3 ; 

 probably never more than 4. They form a slightly diverging 

 tuft and are nearly straight or perceptibly bent outwards. Under 

 a high power of the microscope they appear to be rougli-surfaced. 

 On the minute terminal discs the marginal serration is unrecog- 

 nizable. 



Malformed discoctasters, in which one or more primary 

 terminals stand free without fusing with any of the secondary 

 principals, are of no infrequent occurrence. 



The microdiscohcxaster (PI. XVI., fig. 12) are of the usual 

 appearance and 20 !'■ in diameter, and are found, mostly near the 

 gastral surface, in small numbers and in scattered distribution. 



Finally, as to the basal plate. I have seen this in the 

 specimen shown in PL XVI., fig. 2, which is attached to a 

 Hexactinella lorica. The dictyonal skeletal parts of this sponge, 

 at the place where the said specimen is fixed, are enveloped in 

 a thin, small-meshed, siliceous reticuhun, evidently the limiting 

 basal-plate of the latter. The beams of this plate are sparsely 

 microtuberculate and look quite like those I have figured in PI. 

 XXII., fig. 17, from Rhahdocalyptiis capillaius. Outside that 

 plate and in the sponge under consideration there may possibly 

 occur at places some basidictyonal hexactius, but these were not 

 actually encountered. 



