122 AKT. 7. 1. IJIMA : HEXACTINELLIDA, IV. 



principalia and the shortest and finest comitalia. Those of the 

 smaller dimension nsually have the tips of the rays rounded or 

 somewhat conically shaped. As usual the diactins run either 

 solitarily or in loose bundles of indefinite strength. The paren- 

 chymal fibers may be said to be somewhat coarse ; decidedly so 

 are they in the larger specimen belonging to Mr. Owston, 

 especially in its lower part. 



The prostalia are diactins of moderately large size. It would 

 not be improper to regard them simply as certain parenchymalia 

 that liad protruded themselves to a greater or less extent from 

 the apices of conuli (PI. X., fig. 11). Their outer ends are 

 generally broken off. 



The hypodermalia are likewise diactins, exactly similar in 

 character to the smaller parenchymalia. One large hypodermal 

 diactin measured was 2 mm. long and 27 n thick at the middle. 

 In forming the hypodermal beams, the diactins rwn sometimes 

 singly and at other times combined into bundles in variable 

 number. 



The hypogasti^alia again are diactins which for the most 

 part are exactly comparable in all resj)ects to the hypodermalia 

 or to the smaller parenchymalia. However, one feature peculiar 

 to many of them, but not to all, consists in the fact that the 

 spicular center is externally marked by an annular swelling or by 

 four cruciately disjDOsed bosses, — a feature which is but rarely, if 

 at all, noticeable on either hypoderraal or parenchymal diactins. 

 Precisely the same fact has been noticed by me in certain other 

 Rosselline species. Further, among the hypogastralia with the 



