I7O FLORENCE PEEBLES. 



in fifty per cent, of the nucleated fragments, while removal of 

 the posterior end caused irregular division in only twenty per 

 cent, of the pieces. 



3. Paramecia cut in half transversely usually die as the nucleus 

 is forced out by the pressure of the knife. When the nucleus 

 remains in one of the halves regeneration is followed in that 

 half by normal division. 



4. Monsters develop from fragments composed of more than 

 half of the protoplasm of a normal Paramecium, but never 

 develop when a cell is cut exactly in half. 



5. A fixed division plane is present in the normal cell as early 

 as two and a half hours after fission. It is possible in vegeta- 

 tive cells, where fission has been delayed for a period, that more 

 than one plane is laid down. This would account for the fact 

 that after cutting off one end of the cell several divisions follow 

 in quick succession. 



6. The power of regeneration varies in different races, and in 

 different individuals of the same race. It is the index of the 

 condition of the cytoplasm. 



7. The removal of a portion of the cytoplasm does not result 

 in the production of smaller individuals. After several genera- 

 tions have been produced the normal size is regained. 



BRYN MAWR, PA., 

 May ii, 1912. 



LITERATURE. 

 Calkins, G. N. 



'n Effects Produced by Cutting Paramecium Cells. Biol. Bull., Vol. I, p. 36. 

 Jennings, H. S., and Hargitt, G. T. 



'10 Characteristics of the Diverse Races of Paramecium. Jour. Morph., 



Vol. 21, No. 4. 

 Lewin, K. R. 



'10 Nuclear Relations of Paramecium caudalum during the Asexual Period. 



(Preliminary communication.) Vol. 16, Part i. 

 Popoff, M. 



'09 Experimentelle Zellstudien. 2. Ueber die Zellgrosse, ihre Fixierung und 

 Vererbung. Arch. f. Zellforschung, 3, p. 124. 



