ARTEMIA SALINA 



291 



ARTEMIA SALINA. 



Report of the Committee appointed to investigate the progressive adaptation 

 to new conditions in Artemia salina [Diploid and Octoploid, Partheno- 

 genetic v. Bisexual) (Prof. R. A. Fisher, F.R.S., Chairman ; Dr. K. 

 Mather, Secretary ; Dr. J. Gray, F.R.S., Dr. F. Gross, Dr. E. S. 

 Russell, O.B.E., Prof. D. M. S. Watson, F.R.S.). 



During the year experiments have been carried out on 16,540 tested nauplii, 

 distributed in five lines, of which tw^o have been carried to the fifth, one 

 to the fourth, and the remaining two to the third, selected generation. 

 Table I shows the number of tested nauplii in each generation of each line. 



The large increase in the extent of the experiments as compared with 

 previous years is due partly to the increased amount of time devoted to the 

 care of the cultures by Miss North and other members of the Galton 

 Laboratory, and partly to greater success in obtaining broods, especially 

 during the winter and spring months. More intense illumination may have 

 been one factor contributing to this success. 



The experiments have followed the programme, as originally laid down, 

 of testing each brood in six successive standard strengths of sodium arsenite 

 and selecting, in each generation, survivors from the higher strengths for 

 use as parents. Although, as will be seen, remarkable progressive changes 

 in tolerance were shown in several lines, the difficulty, noted in previous 

 reports, of broods from the same parents showing very unequal mortalities 

 has not yet been overcome. For example, we give in Table II the number 

 tested and surviving at different strengths in two large broods occurring 

 in succession in the unselected generation of C6. It will be observed that 



