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]
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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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    becomes perhaps a ciliated morula, this again a gastrula, with ciliated ectoderm and amoeboid endoderm; this may settle down as in sponges, its cells re-cycling anew, the ectodermic layer becoming amoeboid, the endodermic ciliated (fig. 18). The endodermic cells remain per- manently more or less amoeboid, as the recently much investigated phenomena of intercellular digestion have so clearly established. The amoeboid ectodermic cells, on the other hand, may give rise to muscle—and a muscle is but an amoeba elongated so as permanently to contract along one line ; on the other hand, they may pass into a quiescent state, or throw out encysting material, which may either enclose them individually, as in Ascidians, or form a collective external envelope, as in Arthropods. The mesodermic cells may either remain unspecialised as amoeboid corpuscles, may specialise as muscular tissue, or cycle into the resting state, i.e., develop into connective tissue (see fig. 19). And if the cell cycle persist thus long in the life-history of the organisms, why should it disappear? In reality, it does not disappear completely. The amoeboid corpuscles of the perivisceral fluid of an invertebrate—say an Echinus—develop, largely at least, from the ciliated epithelium lining of the ccelome—permanently exhibit, that is to say, one of the most characteristic phenomena of the cycle. And when under proper precautions we examine a fresh drop of the fluid, we observe the corpuscles as they die running together into a plasmodium,* so perfectly similar to that of a Myxomycete as actually to have been described by a recent observer as a new genus and species, f And this phase of the cycle takes place, in the so-called Coagulation of corpusculate fluids of inver- tebrates generally.:]: Numerous other instances of the occurrence of some phase of the cell-cycle have been recorded, and have already been collected by the writer in a series of papers which have led to the present one; it is unnecessary to call attention to others, save perhaps the especially interesting announcement by Professor Had- don,§ of the occurrence of a plasmodial union of cells during the normal histolysis of Polyzoa. * Geddes, Observations s. 1. fluide perivisceral des Oursins, Arch. Zool. Exp. VIII. + Comptcs Rcndus, t. lxxxii. No. 21. •j- Geddes, On the Coag. of Amoeb. Cells into Plasmodia, &c., Proc. Boy. Soc. Lond.,'^o. 202, 1880, and Trans. Roy. Phys. Soc. Edin., 1S82. § Haddon, On Budding in Polyzoa, Quart. Jour. Micros. Sci., 1883.