66 I. IJIMA : HEXACTIKELLIDA. I. 



dividual raeslies. Structurally the beams are compact, though 

 the constituent spicules are never in fusiou. On their internal 

 surface are to be seen pores, which are the outlets of excurrent 

 canals ; for, the beams possess the chamber-layer, and the inflow 

 and outflow of water evidently take place here as well as in 

 the lateral wall. 



Observations on growing individuals corroborate F. E. 

 Schulze's view ('95, i>. 25) with regard to the origin of new 

 beams and meshes in the sieve-plate. These arise by the split- 

 ting and shifting asunder, as it were, of the beams and nodal 

 plates already jiresent. In other words, there arise in the tissues 

 gaps which gradually enlarge into new meslies. I have also seen 

 evidences of new beams, and tberewith of new meshes, forming 

 themselves along the inner border of the cuff. 



Compared with the sieve-plate of E. regalis as figured by 

 F. E. ScHULZE (19'), that of E. imperialis presents on the whole 

 much larger meshes. 



Whereas the greater upper portion of the sponge-wall 

 possesses a certain degree of flexibility and elasticity, the lower 

 portion is firm owing to the fusion of the principal skeletal 

 elements in this region. As already mentioned, the lower end 

 of the body is well-nigh or quite destitute of the loose tissues ; 

 in fact it may be considered as dead. Some distance before the 

 extreme lower end of the skeletal tube is reached, the exposed 

 longitudinal bands of the rather coarse looking, anchoring fibers 

 begin to become frayed out inferiorly, soon to interlock among 

 themselves and to penetrate into the bulbous mud-ball that always 

 makes up the lower termination of the specimens. Not only the 

 basal tuft but also the lowest end of the internal skeletal tube 



