SILICIOUS AND HORNY SPONGES — WILSON. 495 



Conuli low and not sharp, 3-4 mm. apart. Surface marked with 

 the usual reticulum of narrow bands, 50 p. wide and less, full of sand 

 grains, etc., bounding rounded or angular pore areas. 85-r-200 p. in 

 diameter, that are free or nearly free of foreign particles; bands of 

 this kind radiating from each conulus. Color, silver gray. 



Filaments abundant, 6 p. thick in middle region, tapering toward 

 the pyriform terminations: unspotted. 



Main fibers fascicular, in the Hireinia fashion, only where connec- 

 tives meet them, simple elsewhere: '260-175 p. thick, filled with sand 

 grains and sponge spicules, extending radially into the conuli, one 

 fiber in axis of each conulus, the fiber tapering terminally: the thin 

 dermal layer of foreign particles covering the tips of the fibers as 

 well as the surface in general: all as in Schulze's description. Main 

 fibers at surface of sponge 3-4 mm. apart, the interval decreasing 

 further in. 



The system of connectives varies a good deal. The component 

 fibers may be simple and narrow, about 100 p. thick, or may combine 

 and form flattened plates, about 300-350 p. wide in a radial direction, 

 which are fenestrated by comparatively few and small gaps. What- 

 ever the details be, the connectives establish between the main fibers 

 a comparatively simple and coarse meshwork, the meshes of which 

 are rounded and for the most part 900-350 p. in diameter. The 

 meshes here and there are much larger, up to 3 mm. in diameter. In 

 other places the network is closer and the meshes may run down to a 

 diameter of 150 p. and smaller. In general, an individual connective 

 which meets a main fiber does so by breaking up into a set of branches 

 (''roots"), but sometimes the connection is by a fenestrated expan- 

 sion of the connective or even by an unfenestrated expansion. The 

 connectives include sand grains and spicule fragments, these more 

 often forming only a slender core in the fiber; the foreign particles 

 are sometimes more abundant, but even then less abundant than in 

 the main fibers. 



There are no connectives in the dermal membrane, but the most 

 superficial connectives sometimes lie directly beneath the membrane. 

 The detailed nature of the most superficial connectives of the retic- 

 ulum is inconstant (the inconstancy perhaps associated with 

 growth) ; they sometimes differ noticeably from the connectives in 

 general in that they contain spicule fragments with almost no sand 

 grains and the spongin is pale. 



The skeleton, as will be seen from the above, conforms in general 

 to Schulze's admirable description, but this in its bravity scarcely 

 more than suggests the lines of variation. 



As more specimens assignable to the species are examined, it be- 

 comes evident that the variations are so numerous and intricate that 



