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THE SPONGES OF THE WEST-CENTRAL PACIFIC 



Text Figure No. 86. Thalysias cervicornis. A: Sketch of the entire sponge, X 1/15. 

 This is NOT a camera lucida drawing. B: Style from the fiber. C: Tylostyle from the 

 spaces between fibers, and from the ectosome. The entire spicule is shown, but in two 

 parts. D: Two of the echinating acanthostyles. E: Toxa. F : Two of the palmate 

 isochelas, each in side view. B-F, X 781. 



may be described as pale brownish orange, or flesh color. In contrast, those 

 from Truk are a little duller on the exterior, which may be described as 

 caramel color, but brilliant vermillion on the interior. It is possible that they 

 represent two species, but agreement in other respects is sufficiently great 

 that this differentiation is not here proposed. The consistency was tough, 

 elastic, and horny, owing to the nature of the fibers. The flesh was very 

 soft in contrast to the skeleton. 



The surface is smooth, or micro-velvet, being covered by myriads of 

 slightly projecting erect spicules. The pores are probably located in the 

 ceiling of the obvious subdermal canals, which meander about over the sur- 

 face of this sponge, but close very quickly and do not show in the specimen. 

 The same is true of the oscules in the Ponape specimen. In contrast, in 

 the Truk specimen, definite oscules, 3 to 5 mm in size, were noticed in the 

 field. This is not regarded as of any real significance in separating the Truk 

 and Ponape specimens, because these oscules were phenomenally rapid in 

 closing — even those as much as 5 mm in diameter would close in less than 

 one second's time and could be observed only in an absolutely undisturbed 

 specimen under water. I do not know of any other instance of quite such 

 extremely quick movement in any other species of sponge. 



The ectosome differs both in color and in density from the endosome, 

 but the difference is not great. 



The skeleton consists of a reticulation of fibers of tough spongin, 60 /x 

 to 200 fx in diameter, with a very fine mesh — the meshes in many cases being 

 smaller in diameter than the diameter of the fibers. The latter are crowded 

 with spicules in plumose arrangement. The principal or coring spicules are 

 tylostyles, 4 ju, by 265 n in dimensions. The Truk specimen also contained 

 a few others which are not tylostylote and are shorter and thicker, 7 jx by 



