LIFE-HISTORY OF ROTIFER 249 



of 6.17 days. When these percentages of alcohol are employed, 

 the reduction in the number of eggs deposited is not so marked as 

 in higher percentages, but the difference between the alcohol 

 lines and the line reared under normal conditions is still great. 

 There is little reduction in the average length of life in either 

 percentage of alcohol, just as was the case where 1 per cent and 

 2 per cent were used. 



The alcohol experiment was carried on for twenty-seven weeks 

 in the way just indicated; that is, 100 individuals each subjected 

 to J and ^ per cent alcohol solutions, and 100 controls, were 

 allowed to reproduce for a period of two weeks, when isolation 

 of 100 specimens was made from each line and the egg deposit 

 and length of life for all the individuals determined under each 

 of the three conditions; reproduction continued for another 

 two-week period, then another isolation made, etc., until the 

 end of the twenty-third week. At this time the alcohol cultures 

 were discontinued and progeny from both alcohol lines were 

 returned to malted-milk solution without alcohol. In t^his way 

 it was determined whether the effects of J and ^ per cent alcohol, 

 which had been acting continuously on the progenitors of both 

 lines for twenty-one weeks, had any lasting effect when the 

 progeny were returned to malted milk. At the beginning of the 

 fifteenth week progeny of the line reared in ^ per cent alcohol 

 were isolated and reared in 1 per cent and 1| per cent alcohol 

 for a period of two weeks and an isolation made at the end of 

 this time to determine if under the continuous action of ^ per 

 cent alcohol the organism had developed any degree of resistance 

 to higher percentages. 



The effect of the alcohol upon the organisms themselves was 

 marked only in the higher percentages. In many cases in these 

 percentages the increase in size, which usually continues until 

 near the close of the life-cycle, never took place and the indi- 

 viduals were thin and attenuated ; movement in many cases was 

 reduced even in the young individual, and the adults became very 

 sluggish. In the experiments where a low percentage of alcohol 

 (j, ^ per cent) was employed, the treated organisms resembled the 

 untreated checks except in the number of eggs deposited. 



