Further observations on the movements of diatoms / by Jabez Hogg.

  • Hogg, Jabez, 1817-1899.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Further observations on the movements of diatoms / by Jabez Hogg. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    d'appui on the slide and coverglass. Any and every movement however, must he performed at some disad- vantage in so eonfined a space as that affoi ded by a very shallow cell : a succession of normal movements is scarcely possible under the circumstances. Another disturbing element of even more importance comes into play during the microscopical investigation of minute organisms. The siliceous skeleton of Diatoms belonging to the filamentous order, although enve- loped in a nearly structureless protoplasm, is found to greatly interfere with the interpretation of structure, while it increases the difficulty of arriving at the precise nature and distribution of organs of prehension and progression. Diffraction phenomena, it should be remem- bered, are not confined to lined objects, nor to opaque, semi-opaque or transparent elements; in short they are universal whenever the strictly uniform propagation of luminous waves is disturbed by the interposition of any element of unequal refraction. Diffraction phenomena have always been a great stumbling block in the way of the interpretation of structure of every kind, especially of the siliceous valves of Diatoms. In the present case, however, it appears to me to be simply necessary to limit the action of the prehensile filaments to the boundary of the plastic envelope, or a very little beyond it, and the difficulty in the way of comprehending the movements of the Diatomaceae disappears, although they cannot always be satisfactorily demonstrated. It has been contended that the movements of Diatoms are either produced by cilia numerically arranged through- out the ventral longitudinal line of the valve or pro- jecting from the « foramina » at the extremity. For some