INTRODUCTION 11 



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 "proto- 

 plasm" was coined by Purkinje in 1840. The Protozoa was given 

 a distinct definition by Siebold in 1845, as follows: "Die Thiere, 

 in welchen die verschiedenen Systeme der Organe nicht scharf 

 ausgeschieden sind, und deren unregelmassige Form und einfache 

 Organization sich auf eine Zelle reduzieren lassen." Siebold sub- 

 divided Protozoa into Infusoria and Rhizopoda. The sharp dif- 

 ferentiation of Protozoa as a group certainly inspired numerous 

 microscopists. As a result, various students brought forward 

 several group names, such as Radiolaria (J. Miiller, 1858), Ciliata 

 (Perty, 1852), Flagellata (Cohn, 1853), Suctoria (Claparede and 

 Lachmann, 1858), Heliozoa, Protista (Haeckel, 1862, 1866), 

 Mastigophora (Diesing, 1865), etc. Of Suctoria, Stein failed to see 

 the real nature (1849), but his two monographs on CiUata and 

 Mastigophora (1854, 1859-1883) contain concise descriptions and 

 excellent illustrations of numerous species. Haeckel (1873), who 

 went a step further than Siebold by distinguishing between Pro- 

 tozoa and Metazoa, devoted ten years to his study of Radiolaria, 

 especially those of the Challenger collection, and described in his 

 celebrated monographs more than 4000 species. 



In 1879 the first comprehensive monograph on the Protozoa 

 of North America was put forw^ard by Leidy under the title of 

 Freshwater Rhizopods of North America, which showed the wide 

 distribution of many known forms of Europe and revealed a 

 number of new and interesting forms. This w^ork was followed by 

 Stokes' The freshwater Infusoria of the United States, which ap- 

 peared in 1888. Blitschli (1880-1889) estabHshed Sarcodina and 

 made an excellent contribution to the taxonomy of the then- 

 known species of Protozoa, which is still considered as one of the 

 most important works on general protozoology. The painstaking 

 researches by Maupas, on the conjugation of ciliates, corrected 

 erroneous interpretation of the phenomenon observed by Balbi- 

 ani some thirty years before and gave impetus to a renewed cyto- 

 logical study of Protozoa. The variety in form and structure of 

 the protozoan nuclei became the subject of intensive studies by 

 several cytologists. Weismann (1881) put into words the immor- 

 tality of the Protozoa. Schaudinn contributed much toward the 

 cytological and developmental studies of Protozoa. 



