. General physiology; an outline of the science of life. 146 GENERAL PHYSIOLOGY The cilia of the ciliary wreath of the peristome contract continually and rhythmically, and in this way produce in the water a whirlpool, which is so directed that it sucks small particles, such as detritus, mud, bacteria, algae, etc., which are suspended in the water, into the cell-mouth ; from there, surrounded by a layer of water, they are shoved by contractions of the body into the cell-pharynx, and thence into the endoplasm (Fig. 46). The phenomena may be very easily observed, if, according to Ehrenberg's meth
. General physiology; an outline of the science of life. 146 GENERAL PHYSIOLOGY The cilia of the ciliary wreath of the peristome contract continually and rhythmically, and in this way produce in the water a whirlpool, which is so directed that it sucks small particles, such as detritus, mud, bacteria, algae, etc., which are suspended in the water, into the cell-mouth ; from there, surrounded by a layer of water, they are shoved by contractions of the body into the cell-pharynx, and thence into the endoplasm (Fig. 46). The phenomena may be very easily observed, if, according to Ehrenberg's method ('38), granules of carmine or indigo be mixed with the water. It is seen at once how the Vorticclla engulfs the red or blue granules and forms them in its protoplasm into balls which are surrounded by a cover- ing of water and constitute food-vacuoles. The mode of ingestion cif food by other Infusoria is entirely similar to that of Vorticella. The free-swimming forms frequently seek fixed. Fig. 46.— Vorticella in four successive stages of the process of food-ingestion. An alga-cell is being engulfed into the ccU-moath and taken through the pharynx into the endoplasm. food-masses and engulf them. Many Infusoria even, such as Ooleps, a small, egg-shaped, ciliate form having a delicate lattice- like surface, take in large balls of food which are broader than their mouth-opening by pressing the latter upon the ball by the force of the ciliary contraction so that the mouth-opening, as in a snake, is gradually enlarged. Thus they really suck the food-balls into their bodies (Fig. 47). The ingestion of solid food on the part of the cell is, therefore, in every case brought about by active movements of the cell- protoplasm or its motile organoids. In the ingestion of substances by the living ced, one phenomenon deserves special mention—namely, the fact of the selection of food. Of the various cells living in the same medium, each takes to itself different materials, and such as
Size: 2646px × 944px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookauthorverwornmax18631921, bookcentury1800, bookdecade1890
