244 I. IJIMA : HEXACTINELLIDA. I. 



4. A still more advaoced stage of growth is represented by 

 the two specimens figured in natural size in PL VII, figs. 6 & 7 

 (Mus. No. 461, from Outside Okinose, Dec. 15, 1898). One of 

 these is of an irregularly tubercular shape and is 18 mm. high 

 (fig. 6) ; it is attached to a piece of old basidictyonal mass, 

 presumably of the same species. The other specimen (fig. 7) is 

 a tubular sac broken off at the lower end. In both there is at 

 the upper end a single, thin-edged and relatively large terminal 

 osculum. In the uneven lateral wall, several small parietal oscula 

 have opened, though many others are still represented merely 

 by dimple-like depressions of the external surface. The im- 

 mediate neighborhood of the terminal osculum is smooth-surfaced. 

 The spiculation in both is essentially that of R. okinoseana ; but 

 one point requires special mention, viz., that, though the der- 

 malia are predominantly hexactins, there are still to be seen the 

 original pentactin-dermalia in some numbers. 



In view of the fact that in the young of E. marshalli the 

 delicate beams of the inceptional sieve-plate are exceedindgly 

 liable to become lost by being broken off (p. 108), it might be 

 questioned if a similar loss had not happened to the terminal 

 osculum in the young specimens hitherto mentioned of R. okino- 

 seana. Close inspection of the oscular edge in the two specimens 

 just described, however, has seemed to show no sign of an un- 

 natural severing off of any part of it. 



5. A tubular specimen, contained in the same bottle as 

 those referred to above under (2.) and (3.), has the loAver end 

 wanting but must have originally measured at most 50 mm. in 

 total height, with a diameter of about 12 mm. in the middle 

 of the body. The general character of the external surface much 



