28 THE PROTOZOA 



The distinction which Spallanzani drew between large and small 

 forms was also adopted by O. F. Muller in his classification of the 

 Protozoa. The latter maintained, however, that the lower of his two 

 groups (Infusoria) were formed according to Buff on 's view, from the 

 disintegrated parts of higher organisms. These parts, after the 

 disintegration, collect, forming a slimy scum on the surface of the in- 

 fusion {Zooglced), which formed a most important adjunct in all 

 subsequent theories of spontaneous generation. Minute vesicles 

 arise later from this scum, and these remain as living organisms in 

 the form of " Infusoria," which included bacteria, spermatozoa, and 

 the smallest forms of flagellates. This mode of origin he limited to 

 those Protozoa which have no visible organs or means of locomotion. 

 The other group (Bullaria), which included the larger of the 

 animalcula (worms, ciliated Protozoa, rotifers, etc.), he maintained 

 were formed, as in the higher animals, from eggs. Muller also held 

 that these units mix with the inorganic particles to form the solid and 

 fluid portions of the body of higher forms, while alone, and without 

 contact with foreign matter, they form the nerves and " soul." 



Oken (1805), another advocate of the theory of spontaneous gen- 

 eration, held that all Protozoa arose in a similar manner. Since all 

 plants and animals were built up of these Infusoria, he named the 

 latter Urthiere, although, like Buffon, he held that they were 

 neither plants nor animals. Infusions demonstrated to him that all 

 plants and animals could disintegrate into Infusoria. Small Infusoria 

 at first joined together to form larger ones, and out of their union 

 arose the polyps and higher forms. While the outline of Oken's 

 view would seem to indicate a prophecy of the cell-theory, it is quite 

 evident from his book on creation that he had little real conception 

 of what we now regard as the essence of that theory. 1 



The majority of contemporary naturalists followed Buffon and 

 Oken, either absolutely or with slight modifications. Among these 

 Treviranus ('03), Goldfuss ('20), and Carus ('23) accepted Oken's 

 views, while Lamarck ('15), Blainville ('22), and Bory de St. Vin- 

 cent ('24) followed Muller in restricting spontaneous generation to 

 the simpler and smaller forms. 



Dallinger and Drysdale ('73— '75), taking turns over the microscope 

 by day and night, followed out the life-histories of many of these 

 simpler forms through the process of division and spore-formation, 

 thus showing that the monads arise, as do the higher Protozoa, from 



animaux inferieurs, le changement de demeure, de climat, de twurriture, doit produire pen 

 a peu dans les individus, et ensuite dans Vespcce, des modifications tres considerables qui 

 deguisenl a nos ycux les formes primitives" (cited by Dujardin ('41) from Spallanzani). 



1_ The name " Protozoa," given by Goldfuss ('20), meant the same as Oken's " Urthiere." 

 It did not acquire its present significance until 1S45, when von Siebold gave it a new meaning. 



