158 



FLORENCE PEEBLES. 



B. The Behavior of Cells Cut in Half Transversely. 



It is extremely difficult to cut a Paramecium in half without 

 permanently injuring both halves. The macronucleus almost 

 <- invariably slips out and the pieces dis- 



integrate within an hour or two. If, 

 however, the nucleus is pushed for- 

 ward or backward, as the case may 

 be, into one of the halves that piece 

 lives and will finally divide into two 

 normal individuals. Out of forty cells 

 thirty died without fission, and ten 

 produced new races of the normal 

 size. 



All of the experiments described so 

 far were made, without exception, 

 upon cells in the vegetative condition. 

 None of the cells had recently divided 

 or were preparing to divide. 



C. The Formation of Monsters. 



Calkins ('n) has shown that it is 

 possible to produce from a small frag- 

 ment a mass of such dimensions and 

 structure that it represents many in- 

 dividuals, having several mouths, oral 

 grooves, and vacuoles. I have not 

 succeeded in obtaining more than a 

 dozen of these monsters in the course 

 of my investigations. Most of them 

 developed during the warm weather 

 in the latter part of June. Thinking 

 that the temperature had something 

 to do with their appearance I began 

 a series of experiments under various 

 degrees of warmth above that of the laboratory, but did not 

 succeed in producing any more monsters than at room tem- 

 perature. A brief description of several of these monsters may 

 throw some light on the question of their mode of origin. 



FIG. 3. Diagram giving the 

 history of the formation of 

 three normal races and two 

 monsters from a cell from which 

 the anterior end was cut off. 



