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.

    68/1074 (page 48)
    iV. NitzscUi, N. lanceolata, and N. caintata; also Oom]}honema trumatum, Gocconema cistula, Arthrodesmus quadricaudatus, and' Closterium acerosum. The two last, however, are Desmidieae. In the seven species of Navicula enumerated, from 4 to 20 little stomach-sacs are said to have become filled ■with the iadigo employed as the colouring matter. This effect (as Meneghini remarks) could only be produced by keeping the Diatomeee a long time in water laden with particles of indigo, and often re- newed. Kiitzing deduced an opposite conclusion from these experiments, viz. that they were solid corpuscles which, being seated near an opening, exerted an especial attraction upon the colouring matter. Meyen argued so long since as 1839 (Jahresbericht d. Akad. Berlin), against the supposed stomach-sacs and the entrance of colouring matter within them. His obiections are thus expressed :— On the one hand, I can see no stomach-sacs in the NavicidcB, and never obsei-ved in the Uving and moving Bacillana the colouring matter received at one extremity and carried towards the centre, where these stomach-sacs should Ue, whilst among the ciHated Infusona such observations are easy ; on the other hand, it is not uncommon, especially in the larger species, to see the molecules of the colouiing matter employed, Lie upon the middle of the broad ventral surface, lookmg as if actuaUy withm the organism; but if a glass plate be placed upon the specimen and then carefully removed, the particles of colouring matter are taken away with it. . Even Ehrenberg admitted that the presumed stomach-sacs varied in number, were quite irregular in their disposition in the interior, and not unfrequentiy wanting altogether. This last circumstance, Kiitzing remarks, is opposed to the behef in their digestive functions, since such important organs as stomachs can never be supposed absent. , • ii. Although the existence of this fanciful polygastnc apparatus in the Diatomeee is scarcely worth controverting, yet we may add to the above obiections to it the fact that, in the hands of other expemnenters, the attempt to introduce colouring matter by any definite apertui-es into the frastules of this fanuly has been unsuccessful. f ,„ The arrangement of the mucilaginous endochi-ome, or rather of its pio- minent globules, vesicles, and granules, is sufaciently definite and constaat in the same species to afford useful characteristics. At one time these molecules are diffused rather irregularly; at another they are conectedin a rounded heap towards the centre, whilst at another they ai-e disposed in Hues radiating from the nucleus, or formed in a layer upon f« ^en^aU,— at all times (adds Prof. Smith) having one or several oily globules which occupy in different species different positions but are constant m lumber and position in the same species. The minute granules (he con- Wes i p. 20) are generally accumulated in thin layers towards the internal Sl-waUs^ when the fi-ustule is so turned that this layer of endochi-ome is presented edgeways to the eye, the granules appear to be chiefly aggregated Fnto two pMes appHed to the opposite sides of the frustule ; and when s^^^^ division is in progress and the ceU-contcnts are divided mto two portions S a s paration%r temporary aggregation must -^^-^^J « ^^^Jj^ Se simplest condition of the fi-ustule the contents are diffused over the entire surface of the ceU-waUs, precisely as may be seen in the ceUs of many of the la^er Alg^! or of some water-plants of a higher order, as in the leaves of 'SZ^^^^^^^- 'T' ^ definite peculiar Oil^lt^ S^the ^^^^^^^ iSelSJotof^^^^