172 LORANDE LOSS WOODRUFF. 



In 1841 Dujardin 6 recognized only two species of Paramecium, 

 P. aurelia and P. caudatum, and placed P. versutum of Muller 

 (=- P. busaria of Focke == Loxodes bursaria of Ehrenberg) in the 

 genus Bursaria, though apparently with some hesitancy. 



Claparede and Lachmann in their series of studies ( 1858-1 860) 7 

 distinguished eight species of Paramecium, including P. putrinum, 

 a new species which is still recognized, P. bursaria and P. aurelia. 

 They abolished P. caudatum with the remark "Le P. caudatum 

 Ehr. n'en est certainement pas specifiquement different. C'est 

 une simple variete qu'on pourrait meme a bon droit consideier 

 comme la forme typique de 1'espece." 8 



Thenceforth, for about thirty years, the name Paramecium 

 aurelia was applied indiscriminately to both P. aurelia and P. 

 caudatum. Most of the pioneer studies on conjugation, etc., were 

 made, as we know now, on P. caudatum, though it was called 

 P. aurelia. Then came the first hint which was to straighten 

 out the matter. Maupas in i883 9 noted a difference in the 

 micronuclear apparatus of certain paramecia, which led him in 

 i888 10 to announce definitely that the structure and number of 

 the micronuclei is a distinctive character and thus on this basis to 

 reestablish the two common species of Paramecium. Since 1889, 

 when both Maupas 11 and Hertwig 12 studied the nuclear phenom- 

 ena during conjugation of these forms, P. aurelia and P. caudatum 

 generally have been regarded as distinct species, and the validity 

 of this conclusion has been emphasized by Jennings and Hargitt, 13 

 and by Woodruff 14 using pedigree culture methods. 



Studies on the conjugation phenomena of P. bursaria by 



6 "Histoire naturelle des Zoophytes, Infusoires, etc." Paris, 1841. 



7 "Etudes sur les Infusoires et les Rhizopodes," Geneva, 1858-1860. 



8 Ibidem, part I., p. 265. 



"Contributions a 1'etude morphologique et anatomique des Infusoires cilies," 

 Arch, de Zool. Exp. et Gen., (2), I., 1883, p. 660. 



10 "Sur la multiplication des Infusoires cilies," Arch, de Zo"/. Exp. et Gen., (2), 4, 

 1888, p. 231. 



11 "Le rajeunissement karyogamique chez les cilies," Arch, de Zool. Exp. et Gen., 

 (2), 7, 1889. 



"Ueber die Konjugation d;r Infusorien," Abh. Kgl. bayr. Akad. d. Wiss., 

 Miinchen, 2, Cl. 17, 1889. 



13 "Characteristics of the diverse races of Paramecium," Journ. Morph., 21, 1910. 



14 "Paramecium aurelia and Paramecium caudatum," Journ. Morph., 22, 1911. 



