1 66 



FLORENCE PEEBLES. 



series of experiments on certain pure lines where the average size 

 was definitely ascertained before the operation was performed, 

 and the average length and breadth of all cells arising from small 

 fragments was compared. If these measurements had been 

 made from cells of the first few generations arising from such frag- 

 ments the conclusion would have been reached that it is not only 

 possible, but quite-a simple matter to produce a small race from a 



large one. It is necessary to keep such 

 cultures for many generations until after 

 repeated divisions the normal size is re- 

 gained. The method followed in these 

 experiments may be illustrated by giving 

 one example. All measurements were 

 made with a micrometer under a Zeiss 

 objective 3, ocular i, after the cells were 

 killed in Worcester's fluid. 



Experiment E. The anterior end of 

 the cell was removed (Fig. 15), and as 

 soon as the nucleated fragment divided 

 into a small and a large cell the two in- 

 dividuals were separated. The large 

 piece continued to divide forming a nor- 

 mal race which we shall distinguish as 

 E 1 . The small piece after a period of 

 growth divided irregularly into a small 

 anterior and a larger posterior cell. The 

 descendants of the posterior cell formed 

 a race which is designated as E 2 . The 

 next division of the small piece was again 

 FIG. 15. Diagram show- irregular, the posterior cell exceeding the 

 ing the formation of normal anterior in size. The race formed from 

 races after irregular division < i n j j ITS TU 



this large cell was designated E 3 . 1 he 



small anterior piece at the next division formed two cells of 

 equal size; these were called E 4 . There were then four races 

 E 1 , E 2 , E 3 and E 4 to be compared with the pure line E from 

 which they arose. Careful measurements were made from time 

 to time and during the course of the experiments, and all of the 



