. The cell; outlines of general anatomy and physiology. rophoplasts, the cnicloblasts of Ccelenterata, and, finally, thesheaths of the muscle and nerve fibres, etc. Internal skeletonsare found in the bodiesof a large number ofProtozoa, but especi-ally in great varietyand beauty in Radio-larians. They consistsometimes of regularlyarranged spicules,sometimes of a fine,open trellis-work, andsometimes of a com-bination of the twokindsof structures (Fig.(»6). In some familiesof Radiolarians theyare composed of an or-ganic substance whichis soluble in acids and alkalies, but in most cases, on the co
. The cell; outlines of general anatomy and physiology. rophoplasts, the cnicloblasts of Ccelenterata, and, finally, thesheaths of the muscle and nerve fibres, etc. Internal skeletonsare found in the bodiesof a large number ofProtozoa, but especi-ally in great varietyand beauty in Radio-larians. They consistsometimes of regularlyarranged spicules,sometimes of a fine,open trellis-work, andsometimes of a com-bination of the twokindsof structures (Fig.(»6). In some familiesof Radiolarians theyare composed of an or-ganic substance whichis soluble in acids and alkalies, but in most cases, on the contrary,they consist of silicious material which is united to an organicsubstratum, just as, in the bones of Vertebrates, the phosphatesare united with the ossein. In each species the skeleton has aconstant and characteristic structure, and follows certain fixedlaws during the process of its development (Richard Hertwig,5, 40). Under the name trophoplasts, the highly organised differen-tiated products of vegetable protoplasm are included ; these occur. Fig. 66.—Haliomma erinaceus (from R. Hertwi?, Zool.,Fig. 82) : a external, i internal trellis work ; ck centralcapsule; wk soft extra capsular body; 7i internal vesicle(nucleus). 160 THE CELL as constantly as the nucleus, and possess great functional independ-ence. They are of great importance in the nutrition of plants,for the whole process of assimilation and the formation of starchtakes place in them (Meyer V. 9-11). Trophoplasts are small bodies, which are generally eitherglobular or oval in shape; they are composed of a substance verysimilar to and yet distinct from protoplasm. They are easily de-stroyed, whilst the preparation is being made, by either water orreagents, and are most successfully fixed by means of tincture ofiodine, or concentrated picric acid. They acquire a steely bluecoloration in nigrosin, and thus stand out clearly from the proto-plasmic body. They often occur in great numbers in the cell, andmay activ
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