An Introduction to the study of the protozoa with special reference to the parasitic forms / by E.A. Minchin.
- Minchin, Edward Alfred.
- Date:
- 1912
Licence: In copyright
Credit: An Introduction to the study of the protozoa with special reference to the parasitic forms / by E.A. Minchin. Source: Wellcome Collection.
Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.
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![found in holozoic Protozoa of all classes—namely, the presence in the body substance of symbiotic independent organisms of vegetable nature, as described below. III. A certain number of Protozoa that have no chlorophyll or similar pigment in their bodies are, nevertheless, free from the necessity of preying upon other organisms in order to obtain their sustenance, since they are able to live upon organic substances in solution, the products of the metabolism or decay of other living organisms. Such forms are termed saprophytic (or saprozoic). since their mode of Ufe is similar to that of a saprophyte, such as a fungus. It is not necessary that they should be supplied Avith ready-made proteins in their food, since they are able to build up their protein constituents from substances of simpler chemical nature. Many examples of saprophytic forms are found amongst the free-hving Flagellata. Lauterborn (17) has coined the useful term sapropelic (from the Greek Trr]X6s, mud) to denote a mode of life which must bo regarded as a special type of the saprophytic method, partly also of the holozoic—namely, the mode of life of those fresh-water organisms that live in a mud or ooze composed almost entirely of the decaying remains of dead plants and other debris of a similar nature. A very characteristic fauna occurs under these conditions. IV. Finally, many Protozoa of all classes live as parasites—that is to say, at the expense of some other living being, which is termed the host. These four modes of life can be used only to a very limited extent for classificatory purposes ; it is only possible to do so in those cases where a particular habit of life, long'continued, has resulted in definite structural characteristics, and more especially in the loss of organs requisite for other modes of life—as, for example, in the case of the subdivision PhytoflageUata, of the order FlageUata, where the holophytic habit has become so ingrained that only structural features proper to vegetable life are retained. In other cases it is clear that a given habit of life in different organisms does not necessarily indicate close affinity between them. In the first place, we find closely allied forms living in different ways. Examples of all the four methods of metabolism described above are to be found in the single order FlageUata, and through- out the Protozoa there are commonly to be found parasitic forms closely allied to free-living forms. In the second place, different types of metabolism may be found as transitory phases in the life of one and the same individual or species. Thus the common Euglena (Fig. 4), a flagellate possessing chromatophorcs and living normally in a holophytic manner, is able to maintain itself as a saprophyte if deprived of the sunlight necessary for a holophytic mode of life (p. 188) Striking examples of variability m the mode of nutrition are seen also in the section Clirysomonadma of](https://iiif.wellcomecollection.org/image/b22651822_0030.jp2/full/800%2C/0/default.jpg)
