PARAMAECIUM AURELIA AND PARAMAECIUM CAUDATUM 235 
Calkins, however, found nuclear fragmentation in degenerat- 
ing individuals of caudatum, Wallengren® and Kasanzeff* 
showed that various changes including fragmentation of the mac- 
ronucleus occur when paramaecia are starved, and Popoff?? 
described a large increase in size and fragmentation of the macro- 
nucleus in degenerating caudatum which paralleled the conditions 
observed in specimens ripe for conjugation. He also obtained 
similar changes by subjecting the animals to various reagents.”® 
Mitrophanow”* emphasized the fact that the structure of the 
macronucleus varied considerably under the influence of diverse 
conditions, and he described fragmentation and figured spherical 
pieces which very closely resembled micronuclei. 
It is evident, then, from my cultures that the macronucleus of 
both aurelia and caudatum is subject to great morphological vari- 
ation without appreciably affecting the rate of reproduction, L.e., 
it is entirely normal. It is also apparent from the work of the 
other authors cited that degeneration changes become manifest 
in the fragmentation of the macronucleus. Consequently the 
macronucleus presents no character which is of permanent diag- 
nostic value. 
Micronucleus. Maupas, as we have seen, regarded the micro- 
nucleus as the chief distinguishing character of aurelia and cau- 
datum, and my cultures substantiate his view. Fixed and stained 
individuals show that the micronuclei of the aurelia culture for 
over two thousand generations have conformed in a remarkable 
degree to the aurelia type as described by the French investi- 
gator, and the micronuclei of the caudatum culture have conformed 
to his caudatum type. 
Studies on the life history of Protozoa. IV. Death of the A Series, Jour. 
Exp. Zoél., 1, 3, 1904. 
% Tnanitionserscheinungen der Zelle, Zeit. f. allg. Physiologie, I, 1, 1901. 
*Experimentelle Untersuchungen ueber Paramecium caudatum. Inaug.—Diss., 
Ziirich, 1901. 
27Depression der Protozoenzelle und der Geschlechtszellen der Metazoen, 
Archiv fiir Protistenkunde, R. Hertwig Festband, 1907. 
28Experimentelle Zellstudien III. Ueber einige Ursachen der physiologischen 
Depression der Zelle. Archiv fiir Zellforschung. 4, 1909. 
22T,’appareil nucléaire des Paramécies, Arch. Zool. Exp. et Gen., (4), I, 1908. 
