598 THE WONDER OF LIFE 



The abnormality seems to be induced by the nature of 

 the food ingested. Affected animals appear quite healthy 

 and reproduce freely. He found that although individuals 

 were removed to control conditions (of relative normality) 

 before the eggs were laid, the young developing from these 

 eggs exhibit the same abnormality as that which their 

 parents had acquired during their lifetime, as a direct 

 result of their environment. This result has been con- 

 firmed over and over again. Females with ripe eggs were 

 also removed from control conditions and put into the 

 particular culture which induces reflexion of the valves. 

 The young developed from these eggs were fully normal, 

 showing the persistence of the effects of normal environ- 

 ment. Subsequent broods of these females in the culture 

 became successively more and more reflexed, i.e. the 

 normality wore off just as the abnormality also does. 



In a second set of experiments by raising the temperature 

 (to 28-5 31-5C.) the size of the young Daphnids was 

 greatly reduced in their first, and indeed in all stages. The 

 rate of the life-cycle was also enormously increased, the 

 period from the birth of the parent to the birth of the 

 young being fourteen days at 16 and six days at 30. 

 The number of young per brood was diminished. The im- 

 portant results of the experiment were the following. The 

 specimens developing from eggs laid by parents a few hours 

 after removal from the higher to the lower temperature 

 were almost as small as those born at the higher temperature. 

 The subsequent eggs laid by the same parents, still under 

 control conditions, still remained affected by the smallness- 

 producing conditions, though to a rapidly diminishing 

 extent. 



In a third set of experiments a reduction of length was 



