Races of Paramecium. 497 



with brief characterization; (11) precautions necessary in working 

 with pure races. 



Part 1. Number and Structure of the Micro-nuclei, 



AND the Species Question 



GEO. T. HARGITT 



The organisms in which we are interested were first described 

 by Mtiller in 1773 as Paramecium aurelia. A fuller account, 

 illustrated by figures, is given in MuUer's work of 1786. Miiller's 

 account fits any or all of the different races. Ehrenberg ('38) 

 attempted to distinguish two forms, a larger one, pointed behind, 

 being given the name Paramecium caudatum, while Miiller's name 

 aurelia was reserved for a smaller form, having the posterior 

 end less drawn to a point. There has been much difference of 

 opinion and discussion among later authors as to whether this 

 distinction was justified, and the two names aurelia and caudatum 

 have been used by some authors in a more or less indiscriminate 

 way. The history of the matter down to the time of Maupas 

 cannot be summarized better than in Maupas' own words : ''Ehren- 

 berg and Dujardin had distinguished two large Paramecia, P. 

 caudatum and P. aureUa. Their distinction was based solely on 

 external characters, the first species being held to be more fusi- 

 form and elongated, the second broader and stouter. Stein and 

 Claparede, still from the study of external features, contested the 

 validity of this distinction and reunited the two species under the 

 name of P. aurelia, thus suppressing P. caudatum. This reform 

 was accepted by all the observers that followed. It is thus that 

 Balbiani, Stein, Koelliker, Engelmann, Butschli and Gruber, 

 who have studied the conjugation of a large Paramecium, have 

 all given it the name of P. aurelia. It is further beyond question 

 that they have all dealt with one and the same species. Only 

 JickeH among recent authors appears, to have made anew the 

 distinction of the two Ehrenbergian forms, but he does not tell us 

 on what character he bases it. Nevertheless it is very real, as I 

 hope to demonstrate." (Maupas, '88, p. 230-231). 



