. Cassell's natural history. Animals; Animal behavior. NATURAL BISTORT. protoplasm (witli its innumerable floating molecules, gi'anules, or globules), possibly a network of filaments, and a more or less solid "nucleus"; and this last lias often within it an almost immeasurably small but distinct spot called the "; Such "cells," being endowed with vital force, can absorb and use up water and organic fluids; they have the power of growth, of secreting new mateiials, of producing similar " cells," capable of the same functions as those of the pare
. Cassell's natural history. Animals; Animal behavior. NATURAL BISTORT. protoplasm (witli its innumerable floating molecules, gi'anules, or globules), possibly a network of filaments, and a more or less solid "nucleus"; and this last lias often within it an almost immeasurably small but distinct spot called the "; Such "cells," being endowed with vital force, can absorb and use up water and organic fluids; they have the power of growth, of secreting new mateiials, of producing similar " cells," capable of the same functions as those of the parent " cell" (and even more advanced functions); and in man-y cases they can move freely. The "," secreted or formed by the protoplasm, seems to regulate these vital phenomena, especially germination or reproduction, for it multiplies itself by "fission," by breaking up into germinative particles, and by the formation of "nucleoli," which, in their turn, become "; Even without a "cell-wall," the Amoiha is a true animal "cell"; but the Protamceba, ha%'ing neither " cell-wEll " nor " nucleus," represents only the simple protoplasm of a " ; Such living corpuscles have been termed " Proto- plasts" by some, and "Cytodes"*by others. Such are the free-moving Monera (Prot- ammha), tlie non-nucleated plasmodia of the Myxomyceta, and the amceboid germs of Greyariiut, proceeding from the " pseudo- ; That all these simple organisms, however, are true animals has not yet been satisfactorily determined. " The Amoiha, however," saj's Haeckel, " presents the most simple form of a single- celled (' unicellular') organism in a complete state of development, and in some sort the ideal of an animal ' cell.' Widely distri- buted in fresh waters, on muds and wet earth, and occurring in brackish and salt water also, these animalcu
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