BY E. F. KALLMANN. 



645 



numerous pores, the largest of which measure 60 or 70/.i in 

 diameter: each mesh is accordingly of tlie nature of a pore-sieve. 

 The boundaries or sides of the meshes contain numerous, densely 

 staining, coarsely granular pigment- 

 cells, usually of more or less elongate 

 shape and occasionally exceeding 20/i. 

 in length, and mostly with their long- 

 axes directed parallel to the sides of the 

 meslies. No spicules are present in the 

 dermal layer except a few scattered 

 triehites. 



Skeleton. — Partly owing to the ten- 

 uity of the skeletal fibres, and partly 

 to discontinuities due to the consider- 

 able innnber and size of the main effer- 

 ent canals, the skeleton forms but a verv 

 inconsiderable portion of the total mass 

 of the sponge. It consists throughout 

 (PI. xxxix., fig.5; PL xlii., figs.l, 2) 

 chiefly of ascending multispicular main 

 fibres, running upwards (often more 

 or less sinuousl}') through the sponge 

 in fairly close ap2:)Osition with one an- 

 other, increasing in number by bifur- 

 cation as they go. Excepting in the 

 more peripheral region of the skeleton, 

 however, fairly numerous, paucispicular 

 connecting fibres also occur, which 

 form among themselves and with the 

 main fibres an extremely irregular re- 

 ticulation. The fibres are composed of 

 longitudinally directed, usually fairly 

 closely packed spicules, united (and, in 



Text-fig. 17.' 



the case of the connecting fibres, also usually ensheathed) by a 



* Rhaphoxya typica. Megasclere.s. ShoM'ing also the extremities of the 

 same more higlily niaguified. 



