270 ART. ".— I. IJIMA: HEXACTINELLIDA, IV. 



to the length of 14 mm. or more. They spring out partly isolated 

 and in irregular distribution but more usually in tufts from 

 the top of little tubercle-like prominences of the dermal surface. 

 Within a centimeter's distance from the oscular edge the oxy- 

 diactinic prostalia become entirely replaced by large oxypentact- 

 inic ones, which cover the rest of the external surface down 

 to the basal mass. All the pentactins arise in tufts from the 

 summit of small tubercle-like or papilla-like prominences, which 

 are always of small diameter but may sometimes be 2-3 mm. 

 high. Thej are usually separated from one another by a space 

 of 5-10 mm. In many cases there are only two or three pent- 

 actins in a tuft ; in other cases there may be more than ten. 

 The paratangential heads in a tuft do not all lie in the same 

 level but usually rise to various heights from the dermal surface, 

 representing different stages of the protrusion of the shafts from 

 the latter. Thus, there arises the gossamer-like layer, in places 

 15 mm. thick, over the sponge exterior. The conditions of the 

 prostalia are exactly the same as in E. capillatus {cfr. PI. XXTL, 

 fig. 12, etc). 



On the basal mass there bristle out numerous hair-like 

 prostals. These, on close observation, were found to be simply 

 the shafts of such prostal pentactins whose distal parts had been 

 broken off. 



The dermal surface is rather uneven. Under the lens it 

 shows the dermal layer to be irregularly meshed, which is due 

 to the diactinic dermalia. The comparatively fine hypodermal 

 fibers exhibit a certain regularity of arrangement in so far as 

 they appear to radiate from the base of each prostal tufts. In 

 short, the structure of the ectosomal skeleton is essentially the 

 same as is known to me from E. mollis and E. capillaius. 



