238 BESSIE NOTES 



twenty-five eggs from the second generation in malted-milk 

 solution isolated from each individual. All individuals thus 

 separated deposited eggs of the usual thin-shelled type and 

 there was no indication of the appearance of the male form. 



To sum up, all individuals from the original clone have deposited 

 eggs; no males have appeared during changes in chemical con- 

 stitution of the medium, changes in temperature, or changes in 

 kind and concentration of food. Progeny of individuals recently 

 isolated from 'wild' ancestors likewise show a uniform produc- 

 tion of females. 



So, during the thirteen months that Proales decipiens has been 

 under observation, reproduction has been entirely by partheno- 

 genesis. Although no records have been kept of the generations 

 produced by mass cultures during this entire period, an estimate 

 of over 250 generations is conservative, calculated from records 

 of sixteen to twenty-three generations produced from single 

 ancestors during a period of thirty days' isolation. In this 

 species continuous parthenogenetic reproduction for this number 

 of generations has been accompanied by no evidence of weakening 

 in the race. At the close of the experiment the range of egg pro- 

 duction forlOO individuals in -^ per cent malted milk at laboratory 

 temperature was from 11 to 30 with an average of 19.50; the 

 range of the length of life was 4 to 7 days, with an average of 

 5.80 days. One hundred individuals early in the history of the 

 race under the same conditions, at about the same time in the 

 year, showed a range in egg production of 4 to 23, with an average 

 of 12.79 and a range in the length of life of 3 to 5 days, with an 

 average of 4.65 days. The hatching of eggs in fresh culture 

 medium takes place within twenty-four hours in 100 per cent 

 of the cases, and, barring accidents, the young individual begins 

 to deposit eggs within twenty-four hours after it is hatched. 

 While no definite measurements can be made of the body size of 

 the adult, owing to its constant movements, the dimensions 

 reached by the adult in the later generations are as ^reat as 

 those shown by any of the individuals produced in the early 

 history of the race. Continuous parthenogenesis for about 

 250 generations in Proales, then, has been accompanied by no 



