2 BRITISH FRESHWATER RHIZOPODA. 



Leeuwenhoek (circa 1675), with his simple lenses, 

 began to examine drops of pond-water, and discovered 

 some of the commoner ciliated forms. Continued 

 observation by this naturalist and his contemporaries 

 revealed a variety of life-forms ; and for many years 

 their origin, organization, and functions were matters 

 of lively controversy. The theory, at first prevalent, 

 of spontaneous generation, was in process of time 

 abandoned ; but even so late as the time of Ehrenberg, 

 one of the most assiduous, though not always most 

 accurate, of observers, their unicellular structure, now 

 universally conceded, was doubted. Imagination con- 

 ceived what the imperfect microscopical appliances of 

 the time failed to reveal, and the impression was formed 

 that they were possessed of organs analogous to those 

 of the Metazoa. Ehrenberg (1838) pictured them with 

 many stomachs, and from that fancied character applied 

 to them the title, now obsolete, of Polygastrica. 



The greater perfection and higher powers of modern 

 microscopes have contributed to the elucidation of the 

 structure of the Protozoa and of their life-functions. 

 Structurally they are simple cells, or single corpuscles, 

 of protoplasm. Siebold, Kdlliker, and Max Schultze 

 early demonstrated the groundlessness of Ehrenberg's 

 theory. Dujardin, together with Biitschli, Auerbach, 

 Claparede and Lachmann, Hertwig and Lesser, as well 

 as our own countrymen Dr. Wallich, Mr. H. J. Carter, 

 and Mr. William Archer, extended our knowledge of 

 the tribe materially. More recently the physiological 

 relations and classification of the Rhizopoda have been 

 studied, and the results recorded, by Professor Ray 

 Lankester and others, in the pages of the ' Encyclo- 

 paedia Britannica,' the ' Journal of the Linnean 

 Society,' the * Quarterly Journal of Microscopical 

 Science,' and elsewhere. Naturalists abroad have for 

 years worked unceasingly in the same field, and the 

 scientific publications of Germany, Switzerland, Italy, 

 and France, for more than a generation, have afforded 

 evidence of the keen observation of Green , Gruber, 



