E. MARSHALLI. — TRABECULE. 147 



rounded by three or four adjacent cells, there were sometimes 

 found roundish pores, which should allow the entrance of water 

 into the chamber. In E. marshalli I have seen no trace what- 

 ever of this kind of connection between the cells. It is probably 

 a sort of an accessory arrangement which is not of universal 

 occurrence among the Hexactinellida. 



The trabecule. — These are in general fine and thread- 

 like, in places band-like. The disposition of their branching and 

 anastomosing strongly reminds one of the irregular web woven 

 by certain spiders (tr., PL IV, fig. 22 ; PI. V, figs. 36, 43 ; see 

 also PL VIII, figs. 29, 30). The meshes are of quite indefinite 

 shape and size. Generally speaking, the trabecule stand for 

 the mesenchyme of other sponges, but never and nowhere do they 

 form a bulky mass or a compact layer of any considerable 

 thickness'", though in places they may be expanded into film-like 

 membranes. Such expansions occur here and there in the deeper 

 parts, at points where three or more trabeculse join together, 

 and are in appearance somewhat alike the nodal confluence of 

 the filamentous pseudopodia of certain Rhizopods. 



The same membranous development of the trabeculfe, but on 

 a far greater scale, is seen in certain definite positions, especially 

 on the surfaces delimiting the sponge from the exterior. Her.e 

 belong the dermalf, the gastral and the canalar membranes, as 



*The diagrammatic figure, recently given by Delage and Hérouaed in the 'Zoologie 

 Concrete ' (T. II, PI. 8, fig. 4), representing the relation of parts in tlie wall of EuplecleUa, 

 is fitted to give an altogether erroneous idea of the structure, in that the choanosome is 

 shown as a tliick folded layer of compact ' mésoderme ' inclosing the chambers, wliile botli 

 the ectosome and the eudosome arc given likewise as thick, minutely perforated layers con- 

 nected with the choanosome by solid pillars. Their other diagrams on Pl. 11, relating to 

 the Hexactinellida, are much better. But these, us also the matters embodied in the text, 

 do not call for special couniient, being entirely based on the representations of F. E. Schulze. 



t For the fact that this layer in E. marshalli hardly deserves to be called a membrane, 

 on account of the general thread-like development of its beams, see ante, p. 120. 



