216 ART. 7. 1. IJIMA : HEXACTINELLTDA, IV. 



all be nearly equally rough on account of the presence of mi- 

 crotubercles, but the usual condition is that the prolonged proximal 

 ray is, in comparison with the others, much more pronouncedly 

 rough, the microtubercles on it being developed into distinct, 

 conical and vertically projecting prickles. 



The gastral hexactins are generally so arranged as to form 

 with their paratangentials a continuous quadrate-meshed lacework, 

 in which the sides of the meshes, exactly like those in the dermal 

 lacework, are formed of the two apposed rays belonging to each 

 of every two adjacent gastralia. Occasionally two gastralia lie 

 very close together, making the four laths proceeding from their 

 position three rays strong instead of two. 



In the smallest specimen I have had (G mm. high), the 

 gastralia were quite sparsely i^resent in scattered arrangement. 



No special canalaria were found in the species. 



The oxyhexasters (PI. XV., fig. 10) measure 98-114 // in 

 diameter. They all seem to be normally developed, neither 

 hemihexactinose nor hexactinose forms havins; been noticed. Fur- 

 ther a distinction between those in the periphery of the wall and 

 others more deeply situated can scarcely be drawn. The prin- 

 cipals are usually short but distinct ; sometimes they are quite 

 obsolete. Two to four — commonly three — terminals are borne by 

 a principal. They are generally thin and nearly straight, show- 

 ing a slight roughness at base when seen under a high power of 

 the microscope. In some of the rosettes the terminals may be 

 nearly twice as thick as in others with which they promis- 

 cuously intermingle. 



The above oxyhexasters are not found in the ectosorne, but 

 occur abundantly in the choanosome, especially in the deeper 



