126 ZOOLOGY 



that the elimination has any effect beyond producing 

 (selecting) a race capable of withstanding the disease, 

 except in cases where there is a mixture of races, which 

 respond differently to the influence. In the latter class 

 of cases, the surviving type may be superior or inferior, 

 judged by general standards, to that perishing. Dr. 

 Pearl assumes, however, that the selective action of 

 alcohol or other poisons on the germ cells is such as to 

 eliminate all the weaker gametes, those which under 

 normal circumstances would produce the poorer class of 

 the population. Consequently, if Classes a and c are 

 large, the survivors (Class c) will really be the best 

 gametes,, not improved in any way by the alcohol, 

 but producing better zygotes on the average, because 

 originally more vigorous. The infertile eggs represent 

 the smaller, less viable elements of the ordinary chicken 

 population. 



In the guinea pig, on the other hand, while Class a is 

 approximately as in the fowl, Class b includes practically 

 all the survivors. Few cells escape some injury. Hence 

 Dr. Stockard's results. Why should guinea pigs and 

 fowls thus differ ? We cannot say at present, but it is 

 not surprising that the cells of such different creatures 

 should differ in their resistance to poisons. Analogous 

 differences can be observed in the' same species (e.g., 

 man), with regard to the poisons of different bacteria. 

 In some diseases most or all of those affected perish, 

 while the rest remain uninjured. In others, while some 

 perish and some escape, large numbers are variously 

 injured. As Pearl points out, the results will differ 

 according to the dosage. If the amount of poison used 

 is sufficient, all will fall in Class a ; that is, there will be 

 no offspring. Of course it may not always be possible 

 to attain this result without killing the parents. Short 



