160 r. IJIMA : HEXACTINELLTDA. I. 



concerning the size of the nuclei in the trabeculpe \Yill expLiin 

 itself. It is also plain that, if there prevails a general uniformity 

 of size and appearance among all the nuclei, wliich I hold to be 

 the case, the assumption of the identity of this or that kind of 

 cells "with another should lose all its validity, so long as it is 

 founded on the similarity of their nuclei alone. 



Finally T will mention here, reserving the details of mv 

 observations relative to the point to another chapter, that the 

 thesocytes seem to be one of those kinds of cells which arise directly 

 from the archpeocytes, the transformation being effected simply 

 by gradually accumulating the ' Knollen ' in the cell-body (PL 

 IV, fig. 24). It may perhaps be urged that the arehoeocytes may 

 be present in some species with, and in others Avithont, the cell- 

 outlines, and that the size of the nuclei may likcAvise be a vari- 

 able matter ; but the fact would remain the same that the theso- 

 cytes — the ' Knollen ' cells of «S'. arctica included — develop out of 

 the ' larger nuclei ' of Schulze. 



To resume my own account of the trabecuhT. I have said 

 in effect that these consist of a fused cytoplasm or nucleated 

 protoplasm (syncytium) in the form of threads and membranes. 

 It will be noticed that here recur in a measure the old sarcode- 

 theory, O. Schmidt's ('64), of the sponge ground-substance, and the 

 syncytium-theory, Haeckel's ('72), of the ' exoderm ' in calcare- 

 ous sponges. Whatever fate these theories may have met in the 

 case of other sponges, in the Hexactinellids they may be said to 

 have preserved a certain degree of applicability. As regards 

 the general soft tissue of the Hexactinellida in particular, there 

 were among the older investigators some who termed it the 

 ' sarcode ' (Thomson, '68 & '70 ; Kent, '70) or ' sarcodine ' (Mar- 



