7O WVMAX REED GREEN. 



passage of small unicellular algae. After the first few days 

 rudually thickening film of green alga? grew on the sides of 

 the jars. To insure that slight accumulations of excreta and 

 other waste might not affect them the water was changed every 

 two days. No food was provided other than that which was 

 suspended in the water and which passed through the fine strainer. 

 They were thus subjected to the same culture medium, food and 

 the same night and day temperatures, as they were in the natural 

 environment. It was thus hoped to duplicate as nearly as possi- 

 ble the natural conditions of these ponds and to acquire positive 

 evidence as to the kind of offspring being produced under natural 

 conditions by testing only the first broods produced after the 

 females were collected. It will be noted that the tabulated 

 presentation of this experiment gives the dates of the collecting 

 trips in the first column, the number of specimens secured on 

 each trip in the second column, the dates on which all young were 

 separated from their mothers and placed in other similar jars 

 in the third column, the number of offspring removed on each 

 date in the fourth, the number of offspring which proved to be 

 female in the fifth, etc., Records w r ere kept of more than one 

 brood from the females collected on May 17, May 20 and May 25, 

 and it is interesting to note that the fourth brood produced by 

 the single female collected on May 17 consisted of 50 males and 

 one sexual female. In calculating the percentages of kinds of 

 offspring only those first removed \vere taken into consideration. 

 Of the 524 offspring in this category none is positively known 

 to be male and 98.8 per cent, are positively determined to con- 

 sist of females. All of the first offspring of the 19 females col- 

 lected on April 20, May 16 and May 23 were saved to test for 

 sexuality. It is seen that 95.6 per cent, were asexual, unless 

 possibly there were more than 7 sexual females in the brood of 

 77 produced by the single very large female collected on May 16. 

 Most of this brood died very early and the mother died also 

 without further progeny. Excluding this one female's offspring 

 the percentage of asexual offspring of the other iH females is 

 over 99 per cent. No sexual forms, either male or female, were 

 collected, but a few ephippial eggs were secured by skimming 

 the surface of the ponds and these on dissection seemed to be 



