d’histoire naturelle, art. Arthrodiées) and Mr. Nitzsch (Beiträge zur Infusorienkunde. Halle, 1817) threw later some light on their nature. The first placed them between the two organic kingdoms, and the second acknowledged their animality. After them, the celebrated traveller in Africa and Asia, Mr. Ehrenberg, author of important discoveries, ranged the animalcules, of which we are treating, among the cuirassed Infusoria with feet alternately moving in and out; and about the same time several naturalists, endowed with less perseverance and sagacity, and without recurring to analogy nor to anatomy, placed them in the vegetable kingdom. Professor Agardh, of Lund in Sweden, formed with them a family of plants, which he called Diatomeae, and ranged them in the lowest cathegory of the Algs. He was followed by MM. Lyngbye, Turpin, Meyen, Kützing and others. Greville, Meyen and Turpin gave the best representations of them; Kützing described them in his Synopsis Diatomearum (as wretched a performance as the drawings representing these animalcules), without possessing the means required for similar investigations, nor the knowledge of their remarkable structure.
Though incomplete, this short historical sketch will suffice, I hope, for the intelligence of this Memoir, in which nothing farther is intended than the natural history of the thermal animalcules, which I observed last summer (1834), about the hot springs of Carlsbad.
