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.
63/1068 page 47
![membrane in Pleuwsigma is a remarkable featm-o of that genus, whilst in Gomphonmna (XII. 28, 53), and other genera with cuneate (wedge-shaped) frustiiles, the figaire is due to the greater development of this segment at one end than af the other. In Amphiprora (XIII, 5, 6), Aclmanthes, Himanti- dium (XII. 50, 52), and Melosira, the connecting membrane is striated, and in. BiclcMphia (II. 48), Isthmia (X. 183), and Amphitetras (XI. 21, 22) is cellulate or areolate. In certain genera the connecting membrane takes on an extraordinary- development, which greatly modifies the figure of the fi-ustules. Instead of being hmited to the interspace between the opposed valves, it extends on either side beyond the sutures (XII. 9), presents itself as a band of greater or less width, and acquires an unusual persistence. Under this form it con- stitutes the ' dngulum' of descriptive writers, and is seen in Amphitetras, BidcMpUa, Podosira, and Melosira. In the last, two genera, Prof.^ Smith tells us, the persistence of this circular band is eminently conspicuous, retaioing the fi-ustides after self-division in a geminate union until the self- dividing process is renewed. Contents of FRtrsTTTLES.—Nuclem, supposed Digestive Sacs, JReproductive Vesicles, Sfc.—The organic membrane of the frustules of Diatomese, strength- ened externally by the sOicious plates, encloses within its cell-like cavity a soft mucilaginous substance filled with numerous granules and globules, and usually of a yeUow-brown or orange-brown colour, but at times of a green hue, and technically known as the ' endoclirome,^ or in Eiitzing's phraseology, the ' gonimic substance.' The granular matter is particu- larly aggregated about the organic wall, leaving the central portion more clear. In this clear central space is a transparent vesicle, representing the nucleus of the cell, having the granules frequently collected around it in an annular form. NageU states that the nucleus, enclosing a nucleolus, lies sometimes free in the centre of the fhistular cavity, but at other times is affixed at one spot to the waU., and therefore ' parietal.' He also describes two sorts of nuclei, viz. primary and secondary, attributing to the former the active part. Schleiden represents the nucleus to be primarily concerned in the original formation of the cell, as weU as in its subsequent multi]jlication. by self-division. Among other elements of the endochrome are more or fewer rather translucent globules, which Prof. Smith believes, like Kiitzing, to be secre- tions of the cell, of a fatty or oily composition, and to be the source of the peculiar odour emitted on burning the Diatomese. In support of this view Kiitzing states that he has occasionally seen two coalesce, proving the absence of proper waUs, and expresses his conviction that these corpuscles are akin to the amylaceous secretions of the Desmidie83 and Confervte and the starch-granules of the higher vegetables. These globules are smaller than the nuclear space, and occupy a pretty constant and definite position. The number of these globules is frequently four, often placed near the extremities, or more rarely clustered round the central vesicle. Meneghini (op. cit. R. S. p. 364), alluding to these vesicles, states them to vary in number, size, and disposition at diff'ercnt stages and according to various conditions, oven under tho eye of the observer. ' These apparent oU-globules were caUod by Ehrenbcrg male sexual glands or testes, whilst those other vesicles distributed within the mucilaginous matter, often about the nucleus, were named stomachs. The latter idea he based espcciaUy on a series of experiments to introduce colouiing matter into the interior of tho frustules, in which he believed ho succeeded The species mentioned ave Nnvieula gracilis, N. AmjMsbcenn, N. viridula. N fulva](https://iiif.wellcomecollection.org/image/b21910224_0063.jp2/full/800%2C/0/default.jpg)
