E. MAKSHALLI. — GEX. CliAEACTEKS. 95 



ridges seen ou the gastral surface, are more often composed of 

 several strands of fibers in close union, than of a single compact 

 strand. "With respect to the relation between the different sys- 

 tems of skeletal beams, it may here be mentioned that the 

 oblique beams very frequently blend into the transverse as well 

 as Into the longitudinal beams, besides entering into all sorts of 

 relations at the points where they intersect these. Some oblique 

 beams are plainly seen to pass between these two systems ; some 

 to penetrate through their separate strands or fibers ; and others 

 to pass over even to the inside of the transverse or to the out- 

 side of the longitudinal beams. In short, the oblique system of 

 skeletal beams may be said to permeate the two other systems 

 rather than to occupy an Intermediate position. As a separate 

 system, the oblique beams in E. marshalli are apparently in a 

 state of less differentiation than in many other species, e. g., 

 E. imperialis. I shall have later to return to the adult skeletal 

 beams when I come to treat of quite young specimens. 



The rectangular meshes, formed by intersecting transverse 

 and longitudinal ridges on the gastral surface, are either quad- 

 ratic or somewhat elongated in the longitudinal direction. They 

 are largest at the most out-bulged portion of the sponge, where 

 they may measure 4-6 mm. in length of sides in large specimens. 

 In conformity with the Irregular distribution of the parietal 

 oscula as seen from the outside, no definite rule can be laid 

 down with regard to the relative distribution of the so-called 

 interstitial meshes and those perforated by the oscula. Not 

 infrequently, either kind of mesh may be seen several In 

 succession transversely, longitudinally or obliquely in one direction 

 or the other. 



