Chapter 109

[←105]

This substance, when dry, is tolerably compact, and of little specific gravity: Professor Ehrenberg has examined it: he states (König Akad. der Wissen: Berlin, Feb. 1845) that it is composed of infusoria, including fourteen polygastrica and four phytolitharia. He says that they are all inhabitants of fresh water; this is a beautiful example of the results obtainable through Professor Ehrenberg's microscopic researches; for Jemmy Button told me that it is always collected at the bottoms of mountain-brooks. It is, moreover, a striking fact in the geographical distribution of the infusoria, which are well known to have very wide ranges, that all the species in this substance, although brought from the extreme southern point of Tierra del Fuego, are old, known forms