420 Mr. G. Smith. 



Table I. 



Generation. 



Number of 



Number of offspring. 



Number of 



Number of offspring. 



parents. 



Female. 



iviaie. 



parents. 



Female. 



Male. 





Isolated at 27° 



0. 



Crowded at 27° C. 



1 



5 



35 







20 



47 







2 



13 



43 







20 



65 







6 



13 



80 















4 



4 



14 







10 



20 







5 



1 



22 







16 



28 







6 



11 



103 







20 



171 







7 



12 



331 







16 



147 







8 



9 



253 







24 



105 







9 



7 



120 







16 



20 







10 



6 



75 







8 



40 







11 



9 



112 













Totals 



90 



1188 







150 



643 











Generation. 



Isolated at 10-17° C. 



Crowded at 10 -I 



7°C. 



1 



5 



129 







20 



91 



7 



2 



8 



204 







33 



1035 



100 



3 



10 



319 







70 



482 



15 



4 



10 



157 







27 



242 



8 



5 



9 



168 







30 



190 







6 



7 



144 







65 



415 







7 



3 



49 







75 



452 



36 



8 



10 



250 







30 



470 



65 



9 



11 



253 



56 



15 



40 







10 



6 



99 







30 



87 



25 



11 



7 



88 







25 



60 







Totals 



86 



1860 



56 



420 



3564 



256 













Since it was found that the individuals crowded at 27° C. produced few 

 young and did not flourish, the experiment was subsequently continued in a 

 rather different way, only two kinds of conditions being employed, viz., isola- 

 tion at 27° C. and crowding at 10-17° 0. In this second experiment as 

 nearly as possible equal numbers of parents in each generation were used in 

 the isolated and crowded condition. Also a careful observation was kept to 

 see how many of the parents used became ephippial or sexual. This experi- 

 ment was made some time after the first with individuals that had been 

 propagating by parthenogenesis, so that the first lot of parents used were 

 about the 35th generation from the beginning of the cycle, i.e., the original 

 winter egg from which the first individual emerged. 



