LIFE-HISTORY OF ROTIFER 253 



of 19.50 for checks reared continuously in malted milk. At 

 this time, after three generations spent in malted milk, all the 

 effects of alcohol upon egg production has been lost. 



To summarize: In Proales decipiens individuals of a line 

 subjected to the fumes of J and | per cent ethyl alcohol con- 

 tinuously for nineteen weeks show a decided reduction in egg 

 production while under the influence of the alcohol, but their 

 progenj^, returned to normal conditions, regain the normal 

 egg-producing power after the third generation. 



SUMMARY 



This paper is an account of the normal life-cycle of Proales 

 decipiens, with experimental studies of the production of males, 

 of the effects of selection during parthenogenetic reproduction, 

 and of the effects of alcohol on inherited characteristics. 



1. Statistics are given as to the length of life, the rate of 

 reproduction, the number and kind of eggs deposited, with study 

 of the variations in these matters. The animal lives about a 

 week, then dies with characteristic symptoms of senility. During 

 its life it produces several eggs per day, the number increasing to 

 a maximum, then decreasing with the onset of old age. 



2. Reproduction by parthenogenesis for about 250 generations 

 gave no indication of reduction of vigor in the race in any respect. 



3. During this period, no males appeared. Alteration of the 

 environment by changes in the nature and concentration of the 

 food, bj^ changes in the temperature at which cultures were 

 reared, and changes in the chemical constitution of the medium 

 were not accompanied by the appearance of the male form. So 

 far as known, the species may be quite without males, 



4. An attempt to increase the egg deposit and average length 

 of life through artificial selection carried on for three months, in 

 fifteen generations, was without avail, placing this organism in 

 the list with other parthenogenetic forms in which selection is 

 ineffective. 



5. Treatment with ethyl alcohol in a concentration of j and | 

 per cent for twenty weeks reduced the number of eggs produced 

 from an average of 15 to 24 in normal malted milk to an average 



