PARAMECIUM CALKINSI. 173 



Hamburger 15 and of P. putrinum by Doflein 16 apparently leave 

 no question in regard to the validity of these species, though both 

 species are remarkably similar. 



In addition to P. aurelia, P. caudatum, P. bursaria and P. 

 putrinum, which are accepted by Schewiakoff in his monographic 

 survey of the holotrichous Infusoria, 17 there must be mentioned 

 Paramecium trichium described by Stokes 18 in 1885, and P. 

 multimicronucleata by Powers and Mitchell 19 in 1910. 



Stokes discovered P. trichium in the zooglcea on an infusion of 

 dead leaves. His description, in part, is as follows: 



"It seems to be a distinct species, and one that can scarcely be 

 mistaken for any known form, except possibly for P. bursaria 

 (Ehr.) S. K., differing from the latter, however, conspicuously in 

 form, especially in the apparently oblique curvature of the 

 anterior extremity, in the absence of the truncation of the same 

 part, the absence of the rapid and continuous circulation of the 

 endoplasmic contents, and particularly the green coloration of 

 the cortex and sarcode. The two contractile vesicles, instead 

 of being placed one in each body-half, as in P. bur sat ia, are here 

 anterior and close together, contracting quickly, the one begin- 

 ning to again form almost before the completion of the other's 

 systole. Trichocysts are very abundant, and are so arranged 

 that they seem to elevate the cutictilar surface into the minute 

 hemispherical bosses that covei the entire body. When forcibly 

 extruded through the influence of the glycerole of tannin, the 

 distal end of each, for about one tenth of the entire length, is 

 conspicuously thickened, so that the trichocyst seems to be 

 supplemented by the addition of a minute pyramid." 



Schewiakoff considers P. trichium to be identical with P. 

 putrinum, but if Stokes' description is accurate there is no 

 warrant for this conclusion. Certainly further data are needed 

 before a final answer can be given. 



15 "Die Konjugation von Paramecium bursaria Focke," Arch. f. Protistenk., 4, 

 1904. 



16 "Lehrbuch der Protozoenkunde," 2 Auflage, Jena, 1909. 



17 "Organization et classification des infusoires Aspirolricha (Holotricha auc- 

 torum)," Mem. Acad. Imp. Sci., St. Petersbourg, Classe d. Sci. Phys. et Math., (8), 

 4, 1896. 



18 "Some New Infusoria," Amer. Naturalist, XIX., 1885. 



"A New Species of Paramecium (P. multimicronucleata') Experimentally 

 Determined," BIOL. BULL., 19, 1910. 



