246 ART. 7. 1. IJIMA : HEXACTINELLIDA, IV. 



tubercles. When one end only is thus swollen (PI. XVIIT., fig. 

 4), as is most frequently the case, the spicular center is situated 

 very much nearer to that end than to the other ; the spicule is 

 quite unequally rayed, the ray which is directed towards, and 

 almost or quite touches, the basidictyonal plate, being always the 

 shorter and having the rounded tip. Even in this extreme basal 

 region synapticular fusion never takes place between the parenchym- 

 al spicules, nor between these and the basidictyonalia. 



The smaller parenchymalia, including the comitalia, are of 

 the usual ajipearance and require no special description. 



The marginalia, present on some s])ecimens, are needle-like 

 oxydiactins which may be 10 mm. or more in length and 40 1>- 

 thick in the middle. The similarly shaped prostalia lalGvalia, 

 seen only on small and young specimens, may be 20 nnn. long 

 and 90 1>. thick. Diactins further go to compose the long liypo- 

 gaüral strands. These are combinations of long comitalia-like 

 diactins, 7-35 // (generally about 10 ft) thick and mostly without 

 an annular swelling in the middle. 



The hypodermalia are moderatey large oxypeutactius with 

 paratropal paratangentials. They occur in close groups, generally 

 of 4-8 each (PI. XVIIL, fig. 16), the manner of arrangement 

 being typically that which I have described on p. 131. There 

 are usually in each group one or two pentactins which have 

 entirely smooth paratangentials ; they are always the smallest and 

 the most slender-rayed — i. e., the youngest — of all in the group. 

 The older pentactins being always situated at a higher level than 

 the younger, the shafts of the former obstruct the paratangentials of 

 the latter and prevent them from developing in a regularly cruciate 



