A history of Infusoria : including the Dismidiaceoe and Diatomaceoe, British and foreign / by Andrew Pritchard.
- Date:
- 1861
Licence: Public Domain Mark
Credit: A history of Infusoria : including the Dismidiaceoe and Diatomaceoe, British and foreign / by Andrew Pritchard. 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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![Desmidieee are known to move through considerable spaces. They travel towards the light; appear on the side of the vessel on which the light falls, or rise to the surface and form a pellicle upon it. These, and the analogous fact of their penetrating to the surface of mud in which they have been imbedded, when exposed to light, are phenomena common to the Dcsmidieaj with other Algae. Another proof (writes Mr. Ealfs) of their power of locomotion is afforded by their retiring in some instances beneath the surface when the pools dry up, a phenomenon witnessed also in the case of other plants. Braun S. p. 203) casually refers to this kind of motion, dependent on the resumption of vital action. The Penium curium (Cosmarium curium, Ralfs), which grows in rain-pools which are alternately quickly filled and dried up in the changes of the weather, ascends from the muddy bottom, when the pools fiU, in the form of beautiful bright green clouds, produced by the social growth and the very fluid, widely-extended gelatinous invest- ment of the cells. The movement of this plant, it is added, is more active and more regiilar than that of other Desmidieae, and it is a remarkable sight to behold all the individuals ia a dish of water in a short time turn their long axes towards the hght, and thus aiTange themselves in beautiful streaks in the gelatinous mass. Obsei'vation likewise shows that it is the younger half of the cell, disting-uishable as such for a long time after division, which here timis towards the Hght. Contents of Feonds.—The contents of the fronds or fiiistules of Desmidieae are designated generally by the name of Endochrome. This endochrome, we have already remarked, is of a grass-green coloiu', and contained in a proper sac lining the denser lorica. It is not homogeneous, but presents numerous globules, small vesicles, and many refracting corpuscles; it is commonly not uniformly diffused, but collected in a definite manner, and it either com- pletely fills its sac or leaves it unoccupied at parts, which not seldom are constant in position and aspect. The appearance of the endochrome is modified by age, by external physical circumstances, and by the process of development. Niigeli and Braun describe it as constituting two layci-s within the primordial utricle, viz. an outer and an inner mucilaginous layer, the latter the thicker of the two. Ehrenberg, influenced by his belief of the animal natm-e of the Desmidiaccie, and by his peculiar hypothesis of their polygastric organization, rciirescnted the larger vesicles or globules to be digestive sacs or stomachs, and the smaller green coi-puscles, ova. He even exerted his imagination still fiu-ther, by announcing that in Micrasterias, Arthroclesmus, and one or two other genera, male reproductive stiiictures are visible. These suppositions it is not necessaiy to discuss, seeing that they are unsupported by any facts in the structure and ceconomy of this family. The globules and corpuscles of the endochrome of Desmidieas seem to differ in no respect from those in other Algse, consisting of chlorophyll, starch, and of oily materials floating in a watciy mcdiiun. In most sjiecies of Closterium and of Tetmemorus, some large diaplianous vesicles arc con- spicuous, either disposed irregularly, or more frequently in a single longi- tudinal series (II. 1, 12, 13). Those have the appearance of being distinct cells; and Mrs. Thomas has indeed described two such, of large size, in Cosmarium mrmiaritiferum, as vesicles fiUed with moving granules. No doubt many of the apparent vesicles are nothing more than vacuoles wlrich, as in other protoplasmic substances, tend to arise in the ceU-contents. and may assume a fixity in size and in position. The several species of Closterium, and of Docidhtnu and some of Pniivm, present also, at each extremity of the endochrome (II. 2. 9. ]4). a large](https://iiif.wellcomecollection.org/image/b21910224_0022.jp2/full/800%2C/0/default.jpg)
