10 



THE SPONGES OF THE WEST-CENTRAL PACIFIC 



Text Figure No. 3. Fibers of Hippiospongia communis, subspecies ammata, X 182. 



irregular and almost certainly can be closed, if not entirely at least to a small 

 fraction of their maximum opening. Some of them were found to be as 

 much as 1 cm in diameter. On the upper surface they may be as little as 

 3 to 14 cm apart, but large areas of the sponge will lack them entirely. They 

 have no rim and are not raised. 



The ectosome of this sponge is extremely tough, at least as durable as 

 leather. It is almost impossible to remove it. It is upwards of 50 ll thick, 

 and is loaded with debris. Sponges of this sort were macerated in bacteria- 

 filled water for 2 months, at the end of which time the dermis showed prac- 

 tically no signs of disintegrating or weakening at all, and still needed to be 

 cut off with a knife. There are a few large ramifying subdermal spaces. 

 Over them the dermis is broken rather easily, but still it remains firmly at- 

 tached to the regions between these subdermal canals. 



The endosome is crowded with numerous spherical flagellate chambers 

 about 20 [x in diameter and is also permeated densely with a fibro-reticulation. 

 In this species, as is to be expected in the genus Hippiospongia, the so-called 

 ascending fibers are extremely rare. In specimen number M. 450, one was 

 finally discovered. It was some 80 ll in diameter and loaded with foreign 

 material. The common fibers are very thin in spite of their strength, only a 

 few being more than 20 ll in diameter. Diameters of 9 ll to 17 ll are the rule. 

 The meshes are extremely irregular in outline and size, but more often about 

 100 ll in diameter than other sizes. In places they exhibit a ladderlike or 

 almost fascicular pattern. 



The most typical specimens of Hippiospongia are those from the West 

 Indies. The genus has been sharply set off from Spongia by its possession 

 of large, extensive subdermal canals. These are. not highly developed in the 

 European species communis nor in this variety of that species as reported 

 from the Pacific area. It is referred to the genus Hippiospongia rather than 

 Spongia, however, for many reasons. It does have the large subdermal 

 canals. It has the very resistant and firmly attached dermis. The compara- 

 tive lack of so-called ascending fibers is noteworthy. This new subspecies 



