History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard.

  • Andrew Pritchard
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard. 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.

    107/1074 (page 87)
    some inhospitable and barren districts of Em-ope—for instance, in some locaHties of Lapland and of Hungary, and in other parts of the world. Ehrenberg mentions a sort of earth under the name of Tanah, eaten in Samai-ang and Java, wliich overlays some moimtains of Java at several places at a height of 4000 feet. It is generally solid, plastic, and sticky; it is roUed and diied in tlie shape of small sticks over a charcoal fire, and is eaten as a delicacy. An examination of this earth disclosed 3 or 4 species of Polygastrica and 13 of Phytolitharia. It has been attempted to make the specific characters of Diatomaceous de- posits of critical value in deciding on the date and supei-position of rocks. However, the geographical distribution of these beings is as yet insufficiently known; and every day reveals the fact that species deemed peculiar to some one locaHty are to be foimd in others, and to have at least a very wide range. We have already quoted some exam])les of apparent limited diffusion in oui- remarks on geographical distribution; it is therefore not necessary to illustrate the subject farther in this place. The circumstance that some one or two species seem at times peculiar to a neighboiu'hood, has encoiu'agcd antiquarians to seize on it with the hope of determining the locality whence the clay was procured from wliich ancient specimens of pottery or porcelain were manufactured. Another practical purpose to which the shells of Diatomeee have been put is as test-objects for microscopes, the penetrating and defining powers of which are measured by their ability to detect and demonstrate the existence and nature of ceiiain markings on the surface of the sQicious epiderm—such, for example, as the strije of Pleurosignia. On the naxtjee of Diatome^, ■whether Astiiials or Pl/Usts — various HYPOTHESES.—The nature of the Diatomeaj is still a much-vexed question, although the opinion of those naturalists who hold them to be plants—mem- bers of the great family of Mgss—preponderates. Ehr-enberg assumed their animal nature, and persuaded liimself of the existence of a complicated organi- zation, such as neither the researches of others can confirm nor analogy sup- port. In his latest papers on Organization, he has insisted most strongly on the apparent successful feeding of these organisms with particles of colour which entered within their interior. These experiments are not satisfactory, and have failed in the hands of others; it is besides quite clear, that the umbilicus, at which he represented the colour-granules to enter, is no real opening in the lorica, but a thickening of its epiderm. Prof. Meneghini, now many years ago, penned a learned treatise to prove the animality of the Diatomese; but although he ofiered many ingenious argu- ments to support his opinion, he did not succeed in establishing it. Many de- tails of structure and organization and micro-chemical characters, ui-ged by him in favour of their animal nature, have been considerably modified or entii ely set aside by subsequent researches ; and the general argument, that the varia- tion fi'om recognized plants is in many particulars very marked, has only a comparative or relative force, according to the extent of differential structure of animals which may, on the other hypothesis, be set forth and proved. The distmgmshcd Italian naturalist indeed limits his design in the treatise before us (On the Animal nature of the Diatomeaa, R. 8. 1853) to disputing Jtutzing s arguments for their- vegetable natui'e, saj-ing (p. 365), Whilst unable to confirm or refute the opinions of Ehrenberg, we seem to have observed facts sufficient to disprove those of Kiitzing. P H^T^^-f ^^^^ ranged Focke, Eckhardt (a pupil of Ehrenberg), and 1 rot Jjaiicy, who express thcii- inability to reconcile some of the structural details and physiological phenomena with vegetable organization. Schleidcu