116 I. IJIMA : HEXACTINELLIDA. I, 



part of tlie body. At the upper end, however, it still continues 

 to go on (efr. pp. G8, 82). Here, the new-formation of the trans- 

 verse beams is carried on apparentl}^ to a much later life-i^eriod 

 (as judged by the size) than in E. marshalli, but it likewise 

 seems to stop some time before that of the longitudinal beams 

 is brought to a completion or this end of the body attains its 

 maximum girth. 



Soft Parts. 



As the most readilv obtainable Hexactinellid in the Sa2;ami 

 Sea, E. marshalli has supplied me with my best oi^portunities 

 for the study of the soft parts. The following account, in the 

 absence of special mention to the contrary, refers to that specie?, 

 although in the main it may be regarded as applicable to a wider 

 circle of forms and even to the Hexactinellida in general. As 

 has been stated by F. E. Schulze ('87, p. 23), the histological 

 structure is so uniform throughout the entire group, that the 

 modifications to be noted are hardly of an important character. 



Let it at once be stated that as regards the general arrange- 

 ment of the soft parts, the facts before known through the in- 

 vestigations of F. E. Schulze ('80, '87, '99a, 19'ff), so far as 

 they go, have found essential confirmation in the results of my 

 own observations, though in respect of certain important points 

 relating to the finer structure, my results stand irreconcilably 

 at variance with his. 



The sponge-wall, being composed of the soft parts and the 

 spicules, is, as has been observed by F. E. Schulze, remarkable 

 for the exceedingly cavernous character of its structure. It is 

 thoroughly penetrated by intercommunicating lacunar cavities and 

 passages, across which, it may be said, the soft paits stretch 



