A re-statement of the cell theory : with applications to the morphology, classification, and physiology of protists, plants, and animals : together with an hypothesis of cell-structure, and an hypothesis of contractility / by Patrick Geddes.

Date:
[1884]
Catalogue details

Licence: Public Domain Mark

Credit: A re-statement of the cell theory : with applications to the morphology, classification, and physiology of protists, plants, and animals : together with an hypothesis of cell-structure, and an hypothesis of contractility / by Patrick Geddes. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    observation to exist; in the Gregarine, on the other hand, the amoeboid, state is often practically ignored by classifiers. In tho remarkable Protomyxa of Hssckel, however, we have an organism in which several phases of form are almost equally pro- minent, so that its description as an amoeboid, or a ciliated or as an encysted organism, has been alike impossible. For here is no per- manent highly differentiated form; but an eventful life-history in which one protean mass of protoplasm passes through a cycle of several distinct phases. Let us carefully examine then these phases, since light may thus be thrown upon the life-histories of the higher Protozoa already referred to. Starting then from the encysted stage, in which a mass of proto- plasm is surrounded by a dense envelope, we find that from this after a time (in which division of the protoplasm has in this case occurred), there issues a swarm of somewhat pear-shaped, naked, motile, flagellate organisms. After a brief period of active locomo- tion, these lose their flagellum and their permanent form alike, extrude pseudopodia, in short, melt down into arncebse. After some period of amoeboid life they flow together into a single proto- plasmic mass—unite into a plasmodium, as it is termed, and this after another brief but remarkable period of locomotion and pseudo- podial activity, settles down into a spheroidal mass; this re-encysts ' itself, and the whole cycle commences anew (Plate IV. fig. 1). If now we make a diagrammatic representation of this life-history (or rather form-history, as it should more accurately be termed), of Protomyxa, exhibiting (1) the encysted, (2) the ciliated, (3) the amoeboid, and (4) the plasmodial stages, we shall find that all those temporary phases of form observed among the higher Protozoa may at once be referred to one or other of these (figs. 3, 8). If this be so, those curious phenomena of the exhibition of ciliated forms by organisms usually of amoeboid type like the Eadiolarians, or of amoe- boid forms by organisms almost permanently encysted or motile, like Gregarines or Monads respectively, lose their anomaly, and come under a generalisation at once simple and comprehensive, viz., that a form-history essentially similar to that of Protomyxa (with blanks it is true, but blanks which the progress of discovery is constantly filling up, and may not unlikely almost wholly fill), may be sketched out for all the higher Protozoa; The same idea