Showing papers in "Transactions of The Microscopical Society & Journal in 1854"

Some Observations on the Diatomaceæof the Thames.

Abstract: IN the year 1843 M. Ehrenberg, read before the Academy of Sciences of Berlin a paper on the microscopical marine infusoria of the deposits of the Elbe,* in which he established the remarkable fact that at Gluckstadt, a distance of forty miles, and even above Hamburg, upwards of eighty miles, from the mouth of the riwr, marine siliceous-shelled Infusoria were found alive, and tlieir skeletons deposited in such abundance in the mud of the river, that at the former locality they form one quarter to one-third of the entire mass, and that the proportion is still about half that amount at Hamburg, as far as the flood-tide extends. All his observations gave a great predominance of marine over fresh-water species, even when the salt taste of the water was no longer perceptible. In the lists which accompany this paper, M. Ehrenberg enumerates thirty-four marine species, under the style of siliceous-shelled Polygastrica, the whole of which would now be classed as Algiiz, under the order Diatomacece. The local distribution of these organisms is a point of some interest ; and as well-authenticated lists of species from the different localities in Great Britain have still been only partially attempted, I am induced to lay before the Society the results of some observations on the deposits of the river Thames, which accord in a great degree with those made by Ehrenberg in the Elbe, though the proportion of marine to fresh-water species is more equal at corresponding distances from the sea. The abundance of the Diatomacece, and the facility with which the different species have been collected at Hull, Poole Harbour, and other well-known localities, where they may be gathered alive, and offer such advantages for acquiring an intimate acquaintance with their habits and modes of growth, has tended, in a great measure, to divert attention from those which are deposited by the Thames water ; and, with the exception of some species of Triceratium, Eupodiscus, and a few other forms, the greater part of the list I shall hereafter mention has been hitherto, so far as I am aware, altogether unnoticed, or at all events no special detail of them has been given from that locality. The chief cause, I imagine, for this neglect of the Diutomacece of the Thames and other rivers, has arisen from the fact, that observers have endeavoured to pursue the same plan