. The fauna of the deep sea . e floorof the ocean, and occur in some districts in suchnumbers that the Challenger was able to bring homesome hundreds of thousands of specimens. They aredistinguished from other Radiolaria by the thick outerand thin inner capsule, by the typical main openingor atropyle placed on the oral pole of the main axiswith a radiate operculum provided with a tubularproboscis, and lastly by the presenceof the phgeodium, a voluminous pig-ment body which lies invariably onthe oral half of the calymma andis composed of numerous singularpigment granules of green, olive,16.
. The fauna of the deep sea . e floorof the ocean, and occur in some districts in suchnumbers that the Challenger was able to bring homesome hundreds of thousands of specimens. They aredistinguished from other Radiolaria by the thick outerand thin inner capsule, by the typical main openingor atropyle placed on the oral pole of the main axiswith a radiate operculum provided with a tubularproboscis, and lastly by the presenceof the phgeodium, a voluminous pig-ment body which lies invariably onthe oral half of the calymma andis composed of numerous singularpigment granules of green, olive,16. ^,nen. brown, or black colour,rfof theXi There are many gerrera belong- ttotsfi!phJ: ig to th« Foraminifera that aredium; B, central probably inhabitants of abys- capsule; C, strands ./ i ./ •/ of protoplasm in ^^^^i (depths, but they do not seemthe calymma. ^ ^ After Haeckel. ^^ possess any Special characters, unless it be a greater thickness and density oftheir shells, to distinguish them from their shallow-water PROTOZOA, C(ELENTERA, AND ECHINODEEMA 91 Passing now to the group of the sponges orPorifera. we find that the calcareous sponges are notrepresented at all in the abysmal zone. Two speciesare found at a depth of 450 fathoms, but none aretruly bathybial in habit. The same remark appliesto the horny sponges. These forms chiefly belongto the littoral or very shallow-water fauna, and neverdescend to greater depths than 400 fathoms. Of theother groups of Porifera—the Monaxonia, the Tetrac-tinellidee, and the Hexactinellidae—several genera areknown to extend down to some of the greatest depthsat which trawling operations have been successfullycarried on. It is difficult to point to any characters inthese sponges that can be attributed in any way to theconditions of deep-sea life, but nevertheless we do findin deep water some of the most remarkable and beautifulforms of sponge skeleton that can be found anywhere. Amongst the Coelentera we find in the deep wat
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