12 PROTOZOOLOGY 



the term Protozoa, including in it the coelenterates. Ten years 

 later there appeared d'Orbigny's systematic study of the Foramini- 

 fera, which he considered "microscopical cephalopods." In 1828 

 Ehrenberg began publishing his observations on Protozoa and in 

 1838 he summarized his contributions in Die Infusionsthierchen als 

 Vollkommene Organismen, in which he diagnosed genera and species 

 so well that many of them still hold good. Ehrenberg excluded Rota- 

 toria and Cere aria from Infusoria. Through the studies of Ehrenberg 

 the number of known Protozoa increased greatly; he, however, pro- 

 posed the term "Polygastricha," under which he placed Mastigo- 

 phora, Rhizopoda, Ciliata, Suctoria, desmids, etc., since he believed 

 that the food vacuoles present in them were stomachs. This hypothe- 

 sis became immediately the center of controversy, which incidentally, 

 together with the then-propounded cell theory and improvements in 

 microscopy, stimulated researches on Protozoa. 



Dujardin (1835) took pains in studying the protoplasm of various 

 Protozoa and found it alike in all. He named it sarcode. In 1841 he 

 published an extensive monograph of various Protozoa which came 

 under his observations. The term Rhizopoda was coined by this 

 investigator. The commonly used term protoplasm was coined by 

 Purkinje in 1840. The Protozoa was given a distinct definition by 

 Siebold in 1845, as follows: "Die Thiere, in welchen die verschied- 

 enen Systeme der Organe nicht scharf ausgeschieden sind, und deren 

 unregelmassige Form und einfache Organization sich auf eine Zelle 

 reduzieren lassen." Siebold subdivided Protozoa into Infusoria and 

 Rhizopoda. The sharp differentiation of Protozoa as a group cer- 

 tainly inspired numerous microscopists. As a result, various stu- 

 dents brought forward several group names, such as Radiolaria 

 (J. Muller, 1858), Ciliata (Perty, 1852), Flagellata (Cohn, 1853), 

 Suctoria (Claparede and Lachmann, 1858), Heliozoa, Protista 

 (Haeckel, 1862, 1866), Mastigophora (Diesing, 1865), etc. Of Suc- 

 toria, Stein failed to see the real nature (1849), but his two mono- 

 graphs on Ciliata and Mastigophora (1854, 1859-1883) contain con- 

 cise descriptions and excellent illustrations of numerous species. 

 Haeckel (1873), who went a step further than Siebold by distinguish- 

 ing between Protozoa and Metazoa, devoted ten years to his study 

 of Radiolaria, especially those of the Challenger collection, and de- 

 scribed in his celebrated monographs more than 4000 species. 



In 1879 the first comprehensive monograph on the Protozoa of 

 North America was put forward by Leidy under the title of Fresh- 

 water Rhizopods of North America, which showed the wide distribu- 

 tion of many known forms of Europe and revealed a number of new 



