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THE AMERICAN NATURALIST [Vol. XL V 



greatly reduced. We do not know to what extent the dif- 

 ferences in seed weight which give the low correlation in 

 his population are due to the mixture of races slightly 

 differentiated with respect to their vegetative characters. 

 If this differentiation be considerable, the seed weight 

 character with which Professor Johannsen has chiefly 

 worked, may not be inherited at all in the population 

 providing this population be one composed of individuals 

 with the same vegetative characters. It is not sufficient 

 to be assured that these classic beans differ "nur (oder 

 fast nur) " in seed characters ; more detailed information 

 is much needed, and until it is forthcoming I must differ 

 from most biologists in my opinion as to the importance 

 to be attached to the conclusions drawn from them. 



B. Improvement for any Single Character can not be 

 supposed to be Unlimited 



This is a fundamental consideration too often neg- 

 lected. 2 - A wheat is selected up to its maximum pro- 

 ductiveness, perhaps by getting the uppermost attain- 

 able limit at one choice from a large field. Then because 

 it can not be made to yield all grain and no stubble we 

 are told that selection can only isolate already existing 

 types. A sugar beet can not be all sugar and the cow 

 can not give pure cream. 



In arguing for Johannsen 's theory East 23 concludes 

 that since Illinois is no longer making progress in high 



- The principle, however, has been clearly seen by some biologists. For 

 instance, in his "Foundations of Zoology," Brooks says (p. 165): "A 



