92 ART. T. 1. IJIMA : HEXACTINELLIDA, IV. 



degree or somewhat wavy. The pentactins as seen on surface- 

 view preparations are commonly arranged in groups of two or 

 three, the centers lying more or less closely together. The para- 

 tangentials in each group, together with those emanating from 

 adjacent groups, are brought together into loose bundles, which 

 constitute the l)eams of the irregularly meshed hypodermal lattice- 

 work. Now and then some diactins take part in the formation 

 of the said latticework ; they may therefore be regarded as 

 occasional elements of the hypodermalia. Hypogastrally no pen- 

 tactins occur in the endosome. 



The dermalia (PI. VIL, figs. 2 & 3 ; PI. Vill., fig. 1) are 

 mostly pentactins, not infrequently hexactins and very rarely 

 stauractins. The pentactins are commonly supplied with a boss- 

 like rudiment of the distal sixth ray. The rays are rather 

 strong, measuring 80-110 // in length (as measured from the 

 center) and 8-11 // in thickness at base. They taper perceptibly 

 from the l)ase towards the conically pointed end (a point, which 

 PI. YIL, fig. 3, fails to show). 1'heir surface is throughout beset 

 with conical and ei'ect or nearly erect microspines that give a 

 coarsely shagreen-like appearance to the entire surface of the 

 spicule. '1 he more prominent microspines may be turned ob- 

 li(]uely outwards, Sometimes, l)ut not always, the microspines 

 grow considerably weaker and more sparse towards the base of 

 the rays and the central nude. In the hexactinic form the ]-ay 

 that is distally directed is in no way difierentiated from the 

 rest. I*?een under the microscope the dermal latticework is not 

 in all parts regularly meshed, and where the meshes show an 

 approximately quadrate shape, the paratangentials of separate but 



