96 



THE SPONGES. 



general without a spicular fringe. Nevertheless, in the case of some 

 areas, a feebly developed fringe is present over a part of the lower edge, 

 projecting 3-5 mm., and a dense flattened tuft of spicules projects from 

 the upper edge of one of the areas. The pores are mostly open, measuring 

 up to 300 /x in diameter. In some areas the pores are closed, the membrane 

 at the bottom of the area then appearing not as a reticulum, but imper- 

 forate, white, and opaque. The subdermal cavity, roofed in by a pore 

 membrane, connects directly with large canals passing into the interior. 



The flagellated chambers appear in the sections flattened and about 

 80 /a x 40 /x, or spheroidal and 50-60 /x in diameter. I incline to think 



that the chambers naturally vary a good deal in size 



Large canals 



are rather numerous in the body of the sponge. In the superficial region 



* 



the arrangement of the sponge tissue is distinctly lamellate, the lamellae 

 extending more or less parallel to the surface of the sponge, with flattened 

 lacunar spaces between. This arrangement is confined to the superficial 

 part of the body, but is found at both surfaces. 



Megascleres. 



1. Dichotriaene ; rhabdome straight and evenly tapering to a point, about 

 5 mm. x 85 /x ; protocladus projecting slightly upward, tapering very 

 slightly, 220 /x x 60 /x ; deuterocladus also projecting slightly upward, 

 tapering evenly to a point, straight or slightly curved, 750 /x long. 



At the upper surface of the body the dichotriaenes are abundant ; less 

 abundant at the lower surface. 



In both regions the rhabdomes are set 





obliquely to the surface, not radially. In very many cases the inclination is 

 so oblique that the rhabdome comes to occupy a nearly tangential position. 



About the margin of the pore areas some of the dichotriaenes show the 

 usual modification, the cladomes becoming smaller than elsewhere, the 



deuterocladi in many spicules being short and straight. Among these 

 occur spicules resembling those figured for Thenea eehinata (Plate 12, 

 Fig. 5), and which are obviously close to the protriaene condition. No 

 perfect protriaenes were observed. 



2. Anatriaenes . Somal anatriaenes, Figs. 10 and 12, Plate 12, are 

 fairly abundant in the smaller specimen, rare in the larger. Rhabdome, 

 4-5 mm. by 10-12 /x above, becoming very slender and hair-like; curved. 

 Cladi, 100-204 /x long, nearly straight or slightly curved, tapering evenly ; 



cladome deep. 



The somal anatriaenes accompany the dichotriaenes of the obliquely 



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