LIFE CYCLE OF MM<)( KI'IIAI.US VETULUS. 63 



since these were pmb.ibly not perfectly normal, else they would 

 have lived longer, nor of broods beyond the sixth except to con- 

 sider them in determining the average number of broods per 

 stem mother, since the averages were not materially changed by 

 eliminating them. Accordingly only 24 stem mothers were 

 considered fit to include in the final averages, and for similar 

 reasons the number of mothers in the I-\. and F 3 generations were 

 reduced to 16 and 12 respectively. I was much surprised to 

 note the large proportions of males and sexual females in the 

 broods of these stem mothers. This observation suggested 

 the experiment of rearing several generations to discover the 

 relative proportions of males and sexual females in the first and 

 later generations, to compare the offspring of the stem mothers 

 with that of the females produced parthenogenetically, and to 

 learn what difference, if any, is to be found between the offspring 

 of sexual females after they have passed through the sexual state 

 and of those females which never pass through this state. It 

 seemed that even if passing through the sexual state did not 

 affect the ratio of the sexes, or of asexual to sexual females, in 

 the immediate offspring, that the effect might conceivably be 

 cumulative and would be apparent in the succeeding generations. 

 Hence the sexual and asexual females in the FI generation were 

 segregated and two distinct lines, one sexual and the other 

 asexual, were carried to the F 3 generation. Perhaps the most 

 conspicuous feature in the records of this experiment is one shown 

 only by the individual records of the females, namely that they 

 are variable in the extreme. A given stem mother may produce 

 nearly all males, or one kind of females, for several broods, or 

 throughout her life, or they may appear combined in all propor- 

 tions, just as is shown in the detailed individual records given in 

 experiment 2, female number 41. The most important facts 

 however are to be deduced from the summary given at the end of 

 the tabulated results. In order to facilitate the comparison of 

 results in the sexual and asexual lines in the second and third 

 generations, I have placed the figures in juxtaposition and have 

 reduced them to a percentage basis at the end of the table, 

 besides giving the chief data in simpler form following the main 

 summary of this experiment. Of course the results in all cases 



