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THE AMERICAN NATURALIST 



[Vol. XLVI 



But these results, with one possible exception, were 

 open to the criticism that they probably had to do with 

 mixed lines and could therefore be described by the no- 

 tation we have used. The experiments on pure lines have 

 given no such results. One should not be asked to accept 

 the results of the unguarded experiments and disregard 

 the results of the guarded investigations. 



The one possible exception alluded to above refers to 

 the experiments of Woltereck (Deut. Zool. Gesell., 19: 

 110-173, 1909) on parthenogenetic strains of Hyalo- 

 daphnia and Daphnia where there can be no question of 

 gametic recombination. This experiment is not beyond 

 criticism as will be seen later, but if it were our position 

 would not be affected. The results would still have to be 

 described by some fixed standard but the description 

 would be complicated. Since it is not beyond criticism, 

 there is yet no reason for such a complication. 



Woltereck 's work was primarily to show whether or 

 not acquired characters are inherited. It was a second- 

 ary object to find out whether small variations or distinct 

 sports occurred in the species. Those who use the work 

 as an argument for unit factor modification, therefore, 

 should also accept his inheritance of characters acquired. 



Woltereck tested the effect of selection on seven char- 

 acters. Selection gave no results in five cases. The first 

 supposedly successful case is for difference in head 

 height. In different pure lines he found an enormous 

 effect of environment. He therefore endeavored to plot 

 curves for different kinds of environment, food, tempera- 

 ture, generation number, etc. By comparing these 

 curves he makes an argument for the inheritance of 

 small acquired variations. In the absence of control cul- 

 tures, and from the fact that culture conditions very 

 uniform to Dr. Woltereck may have been somewhat ex- 

 treme to Mr. A. Daphnia, the argument has only the 

 value of the other numerous scholastic defences of in- 

 herited acquirements. It is criticized by Tower in a re- 

 cent publication. Woltereck did obtain one inherited 



