34 



THE SPONGES OF THE WEST-CENTRAL PACIFIC 





'*©*/,' 



Text Figure No. 16. Portion of the fiber of Thorectopsamma xana, X 182. 



The consistency was spongy. 



The surface is conulose, with conules ranging from 0.5 to 2 mm but 

 usually about 1 mm high. They vary from 2 to 6 mm apart but almost al- 

 ways are about 3 mm apart. The pores are 50 ^ to 150 /x in diameter and are 

 scattered. They often occur about one per each square mm. This species is 

 often lipostomous, and the exhalant openings cannot be distinguished from 

 the inhalant ones. The only exception was the single specimen from the 

 Truk Archipelago. In it, there were some definite exhalant apertures, 2 mm 

 in diameter, that could be discerned. 



The ectosome is a fleshy dermis, 15 jx to 20 xi thick, and very tightly 

 attached to the underlying tissues. In a few places, a subdermal canal may 

 be found, and in these places the membrane may be detached. Elsewhere, it 

 is amalgamated to the fibro-reticulation of the endosome. The latter is defi- 

 nitely like that of Verongia in general appearance, exceedingly dense and fine- 

 grained. The flagellate chambers vary actually from 25 /x to 40 /x in diameter 

 but are usually about 30 ii in diameter. 



The skeleton is a reticulation of fibers which are laminated with yellow 

 spongin and almost invariably cored with foreign material. They are not 

 sharply separated into primaries and secondaries. They vary from 150 tt 

 to 270 it, in diameter and have many intermediates. The fact that they are 

 here and there clear of foreign material hardly constitutes a separate category 

 of secondaries devoid of foreign inclusion. Yet their relative abundance 

 raises the question of need for further investigation and deliberation. 



The species xana is not a typical Thorectopsamma. It bears some re- 

 semblance to the genus Cacospongia, which is characterized by having pri- 

 mary fibers of the type found in xana, but secondary fibers of a distinct cate- 

 gory which is regularly devoid of debris. Its type is Cacospongia mollior, 

 and its author (Schmidt, 1862, page 27) said that its color was yellowish white 

 and that it became darker in the air or in alcohol. The lack of emphasis placed 

 upon this description makes it seem unlikely that the change was as striking 



