PROTOZOA. 541 



PROTOZOA (INFUSORIA AND RHIZOPODA). 



Ehrenberg's observations on the external and internal 

 structures, as well as on the habits of the Infusoria have 

 been briefly collected by Gravenhorst (Naturgeschichte der 

 Infusions-thiercheii nach Ehrenberg's grossem Werke iiber 

 diese Thiere, 1844), and a synoptical view of the genera, 

 without addition, however, of the generic characters, has been 

 given according to Ehrenberg's classification. 



Ehrenberg (Bericht iiber die Verhandl. der Akad. d. 

 Wissensch. zu Berlin a. d. I. 1843, p. 161, u. 259) found in 

 the deposits of the Elbe, near Hamburg and Gliickstadt, abun- 

 dance of the microscopic shields of marine Infusoria, belong- 

 ing to the siliceous-shelled Polygastrica and calcareous-shelled 

 Polythalamia. His examinations of the mud of the Scheldt 

 and Ems afforded similar results, as did that of the marine 

 deposit in various littoral regions of the North Sea and 

 Baltic. In the course of these researches five new r genera 

 and many new species were discovered. He has also con- 

 vinced himself of the enormous proportionate extent and 

 intensity of life in the highest latitudes, both at the south 

 and north poles, and at the greatest attainable depths of the 

 ocean. (Ib. 1844, p. 182.) Ehrenberg arrived at this con- 

 viction from the examination of the oceanic materials with 

 which he was furnished from the antarctic voyage of Captain 

 Ross, and also by Messrs. Schayer and Darwin, and which 

 afforded him the rare opportunity of investigating the amount 

 of life in the water taken from the polar sea in 70-78 S. L. 

 The same indefatigable explorer of microscopic organisms 

 recognised in dust, which fell upon a ship out at sea in the 

 Atlantic Ocean, various siliceous Polygastrica, and has shown 

 that this dust was derived from a desiccated marsh. (Ib. 1844, 

 p. 194.) He also recognised various siliceous Polygastrica, 

 and calcareous Poly thalarnia, with nine new species, in samples 

 of the marine deposits in the Sea of Marmora and the 



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