GENERAL CONSIDERATIONS 11 



stretched out one against another, they could not reach to the length of 

 a grain of coarse sand." Later he discovered parasite Protozoa in man 

 and beast, and bacteria in the human mouth. Of course Leeuwenhoek 

 made many other discoveries during his long life — his studies were not 

 confined to animalcules — but it is enough that he is justly regarded as 

 the Father of Protozoology and Bacteriology (Woodruff, loc. cit., p. 3). 



Obviously an immense field awaited intensive study, and this was be- 

 gun in a desultory way by many amateur and professional biologists dur- 

 ing the closing decades of the eighteenth century, the outstanding con- 

 tributions being made by O. F. Miiller in 1773 and 1786. And then 

 over half a century passed before Ehrenberg, in 1838, and Dujardin, in 

 1841, afforded a sufficiently broad view of the "simple" animals to justify 

 the establishment of the phylum Protozoa by von Siebold in 1845 

 (Woodruff, loc. cit., p. 4). 



Miiller, adopting the Linnasan nomenclature, described and named 

 some 378 species, of which about 150 are retained today as Protozoa. 

 His classification was the first successful attempt to bring order out of 

 the heterogeneous collection of forms included under the name animal- 

 cula. He used Ledermiiller's (1760-63) term Infusoria for the name of 

 the entire group, which he placed as a class of the worms (see Biitschli, 

 1883, p. 1129). While he eliminated many inaccuracies, he confirmed 

 the substantial observations of the earlier observers, extending many of 

 them to all groups of the Protozoa. He ascertained the presence of an 

 anus, showed that many Infusoria are carnivorous, and observed the 

 process of conjugation, his description of the latter being more accurate 

 than that of any of his followers until the time of Balbiani, in 1858-59- 



Like his predecessors, Miiller included among the Protozoa many other 

 organisms, placing here diatoms, nematode worms, Distomum larvae, 

 and larval forms of coelenterates and molluscs. The majority of these 

 miscellaneous forms were, however, properly classified before 1840, 

 while finally spermatozoa (discovered by Ludwig Hamm, who is said 

 to have been a pupil of Leeuwenhoek) and which had been universally 

 regarded as animalcula inhabiting the seminal fluid, were withdrawn 

 during the last century. 



Following John Hill (1752), MuUer did not regard the Protozoa as 

 complicated animals, but considered them as the simplest of all living 

 beings, composed of a homogeneous gelatinous substance, a view m 



