THE INGEST ION AND EXCRETION OF SOLID BODIES in 



of a plasmatic membrane, disturb in any way the general principles by which 

 absorption and diosmosis are regulated. 



SECTION 19. The Ingestion and Excretion of Solid Bodies. 



In virtue of its physical properties, the protoplast has the power 

 of allowing a solid body to pass through it, without forming any passage 

 through which non-diosmosing substances might enter. The plasmodia 

 of Myxomycetes, and other gymnoplasts exhibiting amoeboid movements, 

 make extensive use of this power, and thus particles of indigo placed near 

 a plasmodium are soon taken in to a considerable extent (Fig. 7). All 

 sorts of substances, including oil-drops and small living organisms, may 

 be ingested, and, indeed, it seems probable that the readiness with 

 which solid bodies are taken in by the plasmodia of Chondrioderma or 

 Aethaliinn depends indeed solely upon mechanical factors. The solid 

 particles are carried by streaming movements to the interior, and may 

 in part penetrate the vacuoles, while from time to time they are ejected 

 again, so that in clear water a plasmodium may 

 free itself from all foreign particles in from one 

 to two days T . 



Similarly, crystals and other solid bodies 

 naturally produced or introduced artificially, may 

 be transferred in dermatoplasts from the protoplasm 

 to the cell-sap, or in the reverse direction, but the 

 cell-wall prevents any escape externally, although 

 a passage through the plasma may be possible. 

 Organisms which bore through the cell-wall can FlG . P ,, rtion of a p i as mo- 

 penetrate the protoplasm without difficulty, and j^L. ^^orelgn'bf^sb^g 



. r 1,1 -A. r il ing-ested at a. while internally 



other facts show that, were it not tor the presence various ingested particles are 

 of the cell-wall, solid particles could be taken into (x^ooo' '" 

 the cell with comparative ease. Indeed, oil appears 



to be absorbed in the form of minute droplets (Sect. 16), and the processes, 

 by means of which gymnoplasts ingest their nutritive material in greater 

 or less degree, apparently attain, under certain conditions, considerable 

 importance in dermatoplasts. At the same time, a power of throwing 

 out useless substances or excreta is equally necessary to a gymnoplast, and 

 the mode of nutrition of a Myxomycete is therefore essentially that of an 

 animal. In the higher Protozoa, ingestion and excretion occur at a certain 

 localized region, and ultimately this becomes a well-defined oral aperture. 



1 Details by Pfeffer, Aufnahme u. Ausgabe ungeloster Korper. 1890, p. 150; Celakovsky, Hora, 

 1892, Erg.-bd., p. 182. The older literature is given here, and also an account of the culture and 

 treatment of Myxomycetes. Of the more recent literature concerning Amoeba, the work by Dantec, 

 Ann. d. 1'Inst. Pasteur, 1890, iv, p. 776, and 1891. v, p. 170, may be mentioned. 



