SPONGES— WHITELEGGE. 463 



Megascleres : — straight or rarely curved strongyla with evenl}'' 

 rounded ends, perfectly cylindrical, and devoid of any tendency 

 to an oxeote character. Size 0-16 mm. by 0-006 mm. 



Microscleres : — simple C-shaped bodies about 0-014 mm. long ; 

 they are few in number and difficult to find. 



This species dijBFers from other members of the genus in its 

 peculiar spicular characters both as regards shape and size. 



RAPHISIA, Topsent. 



RHAPHISIA RAMOSA, sp. nov. 



(Plate xliii., fig. 4.) 



Station 44. 



Sponge consisting of a number of coalescent branches with from 

 three to four longitudinal grooves. The branches are somewhat 

 contorted and vary considerably in length ; the longest are about 

 70 mm. and the shortest 50 mm. The diameter of the branches 

 ranges from 5 to 10 mm. Each branch exhibits several longi- 

 tudinal grooves in which are situated a few irregular oscula (?) 

 from 2 to 5 mm. in diameter, and the surface generally is more or 

 less finely porous. 



The skeleton is somewhat complicated and difficult to diagnose, 

 inasmuch as the real arrangement of the spicules is obscured by 

 a peculiar cellular covering which resembles some of the unions 

 between an alga and a sponge. 



In sections mounted in glycerine the sponge presents features 

 which are like those of the sponge and the alga combined, yet 

 the latter is so indefinite that it is difficult to say whether it is 

 part of the sponge or an alga. 



On the other hand, in sections mounted in Canada balsam the 

 algal features are obscured and the spicular characters are 

 rendered distinct, but the cellular elements present— in the form 

 of the cell walls — tend to the impression that there are irregularly 

 shaped microscleres scattered throughout the body of the sponge. 



Thin longitudinal sections mounted in glycerine present a sub- 

 continuous surface, with here and there dense cellular looking 

 fibres which form a close but irregular network of primary and 

 connecting branches, the inclosed spicules being barely visible 

 except where they are exserted. Similar sections mounted in 

 Canada balsam exhibit the disposition of the spicules; they form 

 loose whispy bundles which run more or less longitudinally with 

 rather indefinite connecting branches and an abundant supply of 

 scattered spicules throughout the ground substance. 



