Doncaster Microscopical and General Scientific Society.

A meeting in the Grammar School o Wednesday evening week, Dr. J. Mitchell Wilson I the chair. A paper on “Diatoms” was read by Mr. J. M. Kirk. ¹

Diatoms have long been considered to be the remains of animalcules and most of the older microscopists treated them as such. Although the question is far from being settled, they are now generally considered as belonging to the vegetable kingdom. Diatoms, like Desmids, are simple cells having a firm outer coating within which is enclosed an endochrome. The diatomacdeae are divided into two chief groups – those which are single frustules and those which cohure in masses.

The name seems to have been given to them from the readiness with which the latter may be cut or broken through, hence they are sometimes called “brittle worts”. During the healthy life of a Diatom the process of self-division is continually being repeated, and a very rapid multiplication of frustules then takes place, all of which are repetitions of the same individual form. These original forms are of great variety.

A large part of the infusorial earths deposited at the bottom of lakes is composed of diatoms, one such remarkable deposit being the tripoli or rotten stone used for polishing metals. The well known Turkey Stone, also “Silicon” now sold for polishing paste, is similarly composed. Such is the abundance of Diatoms in some rivers and estuaries that their rapid increase is affirmed by Ehrenberg to have exercised an important influence in blocking up harbors and diminishing the depth of channels.

It is remarked by Hooker that the universal presence of this invisible vegetation throughout the South Polar Ocean is a most important feature, since there is a marked deficiency in this region of higher forms of vegetation; and were it not for them, there would be neither food for aquatic animals, nor (if it were possible for these to maintain themselves by preying on one another) could the ocean waters be purified of the carbonic acid which would be continually imparting to them. A Diatomaceous deposit is met within Sweden and Norway under the name of “Bergmehl,” or mountain flour, and in times of scarcity the inhabitants mix this with their dough in making bread.

Mr. Kirk explained the method for collecting, preserving and mounting the various Diatoms, and illustrated his paper by a large number of beautifully executed drawings of typical forms, among the more elaborate of which may be mentioned the representations of Arachnoidiscus, Heliopelta, and Isthmia.

A discussion followed, after which a vote of thanks was proposed by Mr. Selby & seconded by the Rev. Geo. Smith. The meeting then resolved itself into a Conversazione, many microscopes being exhibited showing specimens of Diatoms.

[This paper was read at the ordinary meeting of 8 March 1882. It would seem very likely that Mr. Stiles has sent this (and other) report(s) to the local newspaper(s), as the text is the same as that which appears in the minute book, except for a few minor changes.]

Notes

1. For more information regarding the modern preparation of Diatoms for the microscope, see here