8 THE PROTOZOA 



contractile vacuole of Vorticella, with its regular pulsations, to a 

 beating heart, while Spallanzani, distinguishing the vacuole from its 

 canals, assigned to it the function of respiration. The mouth was 

 found in a number of forms, by Gleichen, who first used the now 

 common experiment of feeding the Protozoa with minute particles 

 of colored substances, such as carmine, indigo, etc. A considerable 

 knowledge of reproduction was also obtained. Longitudinal division, 

 discovered by.Trembley (1744), was confirmed by Spallanzani, who, in 

 addition, observed transverse division in no less than fourteen species, 

 while his friend Saussure followed out for the first time the division 

 of an encysted Colpoda ; an observation confirmed by Corti and 

 Gleichen as well as by Spallanzani himself, who saw a Colpoda slip 

 out of its cyst, which he not unnaturally mistook for an egg-case. 



These early discoveries were, in most cases, so bound up with fan- 

 tastic speculations that their zoological value was greatly impaired. 

 Many of these early inaccuracies were, however, weeded out by 

 Otto Friedrich Miiller (1786), to whom we are also indebted for the 

 scientific naming of the Animalcula, which up to his time had been 

 called by long descriptive names given according to the fancy of each 

 observer, and often based on far-fetched resemblances. Miiller, 

 adopting the Linnaean binomial nomenclature, described and named 

 some 378 species, of which about 150 are retained to-day as Protozoa. 

 His classification was the first successful attempt to bring order out 

 of the heterogeneous collection of forms included under the name 

 Animalcula. He used Ledenmiiller's {\"/6o-'6^) term Infusoria, for 

 the name of the entire group, which he placed as a class of the 

 worms. 1 While he eliminated the 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 predecessors or 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 ccelenterates and molluscs, as well as the 

 rotifers. The majority of these miscellaneous forms were, however 

 properly classified before 1840. The larvae of molluscs and ccelente- 

 rates, and the worms were the first to be removed from the "animalcula " 

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

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

 regarded as Protozoa inhabiting the seminal fluid, were withdrawn 

 during the present century. 



J Cf. Butschli ('83), p. 1 129. 



