144 I. IJIMA : HEXACTINELLIDA. I. 



19'«) has always represented these to be smooth-edged roundish 

 pores of different sizes, oj)ening through the membranous 

 chamber-wall in variable numbers and in irregular distribution. 

 I should think this amounts to about the same as to say that 

 only a limited number of the numerous meshes of the reticular 

 membrane are open, which in my view should be the case with 

 all. 



I beg to remark tliat when insufficiently stained, or Avhen 

 subjected to macerating influences, the choanocytal protoplasm 

 appears quite ill-defined as to its limiting contour ; and then, 

 especially if there should be found in the quadrate meshes some 

 granules or strings of granules, — which in reality belong either 

 to the finer branch-beams or to the terminal branches of certain 

 trabecule, and which in other cases seem to be due to dis- 

 integration of the protoplasm, — one may easily be led to think 

 that the meshes are overspread with a transparent film, while 

 here and there may occur such as happen to be exceptionally 

 clean within, but, which being surrounded by a granular tract, 

 may be taken for the only ones that are open. 



Thv'dly, as regards the general shape of the choanocyte. 

 According to Schulze, it should be nearly cylindrical in the 

 living state and somewhat wine-glass-like when preserved. Dis- 

 tally to the thin basal expansion already referred to, there should 

 follow an elongated neck-like section of the cell-body, which 

 section reminds us of the collum or rostrum of the choanocytes 

 in other sponges. The parts in question in consecutive choano- 

 cytes were observed to be separated by a system of narrow 

 interspaces. Distally they broadened, becoming somewhat trumpet- 

 like, and were finally capped each with a broad collar. A deli- 

 cate central axial-thread extended from the center of the distal 



