INFUSORIA. 25 



Infusoria were discovered towards the end of the 17th century 

 in a vessel of stagnant w r ater by A. von Leeuwenhoek, who made 

 use of a magnifying glass for the examination of small organisms. 

 The name Infusoria, which was at first used to denote all animalcule 

 which appear in infusions and are only visible with the aid of a 

 microscope, was first brought into use by Ledermiiller and Wrisberg 

 in the last century. Later on the Danish naturalist 0. Fr. Midler 

 made valuable additions to our knowledge of Infusoria. He observed 

 their conjugation and their reproduction by fission and gemmation, 

 and wrote the first systematic work on the subject. 0. Fr. Miiller 

 included a much larger number of forms than we do nowadays, 

 for he placed among the Infusoria all invertebrate water animal- 

 cule without jointed organs of locomotion and of microscopical 

 size. 



The knowledge of Infusoria received a new impulse from the 

 comprehensive researches of Ehrenberg. The principal work of this 

 investigator, "Die Infusionsthiercheri als vollkommene Organismen," 

 discovered a kingdom of organisms hardly thought of. These were 

 observed and portrayed under the highest microscopic powers. Many 

 of Ehrenberg's drawings may even yet be taken as patterns, and are 

 hardly surpassed by later representations, but the significance of the 

 facts observed has been essentially corrected by more recent investi- 

 gations. Ehrenberg also conceded too great an extent to the group 

 of Infusoria, including not only the lowest plants such as Diatomatw, 

 Desmidiacece, under the name of Potygastrica anentera, but also the 

 much more highly organized Rot if era. As he chose the organization 

 of the last-named for the basis of his explanations, he was led into 

 numerous errors. Ehrenberg ascribed to the Infusoria mouth and 

 anus, stomach and intestines, testis and ovary, kidneys, sense-organs, 

 and a vascular system, without being able to give reliable proofs of 

 the nature of these organs. There very soon came a reaction in the 

 way of regarding the Infusorian structure ; for the discoverer of the 

 lihizopoda, Dujardin, as well as von Siebold and Kb'lliker (the latter 

 taking into consideration the so-called nucleus and nucleolus), referred 

 the Infusorian body to the simple cell. In the subsequent Avorks of 

 Stein, Claparede, Lachmann, and Balbiani numerous differentiations 



der Infusorien." Jen. Zeitschrift, Tom. VII., 1873. 0. Biitsclili, Studicn iiber 

 die ersten Entwickclungsvorgangc dcs Eizclle, die Zcllthciluny und die Conjuga- 

 tion dcs Infusorien, Frankfurt, 1876. Saville Kent, A Manual of th<; Infusoria, 

 London, 1880-2. Alaupas, " Sur la multiplication des Infusoires Cilies." Arch, 

 d. Zool. Exp. (2), 6, and "La Rajeunissement Karyogamique chez les Cilies, 

 ibid. (2), 7. 



