THE SPONGES OF THE WEST-CENTRAL PACIFIC 



123 



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Text Figure No. 76. Spicules of Hiattrochota ditrochota, X 781. A: Strongyle from the 

 ectosome. B: Style from the endosome. C: Raphide. D: Amphidisc microsclere. 



bright purple colloid was given off. The consistency was tough and stiffly 

 spongy. 



The surface is rough, irregularly conulose. The pores and oscules close 

 so promptly that they could not be made out. 



The ectosome consists of a fleshy dermis about 10 /x thick. The endo- 

 some is permeated by an irregular fibro-reticulation and is abundantly pro- 

 vided with protoplasmic material. 



Whereas reference is made to fibers, the structures in question are so 

 vague and irregular that dimensions are scarcely appropriate. They are 

 crowded with spicules. The megascleres are roughly divided into dermal 

 and endosomal type, but the distinction is not hard and fast. Most of those 

 near the surface, but also some which line the larger canals, are strongyles 

 6 ix by 144 jx in dimensions. Most of the spicules which core the fibers and 

 are scattered loosely throughout the flesh are styles of the same dimensions, 

 6 [i by 144 /x. The microscieres include raphides, 0.5 (x by 110 [x, and am- 

 phidiscs or birotulate spicules 11 p to 12 /x in length. There seem to be at 

 least 8 clads at each end or head of these microscieres, but the exact number of 

 clads is difficult to make out because of the small size. 



This species is unique in the genus Hiattrochota for the ramose form 

 and for the raphides, which are also worthy of a special comment. Attention 

 is called to the fact that in external shape this species is very much like some 

 of those in Iotrochota. The thin film of yellowish-green is strongly reminis- 

 cent of Iotrochota birotulata of the West Indies. Thus, this species has as 

 perhaps its closest relative sponges which are still in a different family, 

 namely Desmacidonidae. It is well to anticipate that at some future date 

 there may be a considerable reshuffling of genera and even families within 

 the orders Haplosclerina, Poecilosclerina, and Halichondrina. 



The specific name is from the Greek, as descriptive of microscieres. 



