No. 556] SHORTEB ARTICLES AND DISCUSSION 239 



Shull, G. H. 1911. Reversible Sex-mutants in Lychnis dioica. Bot. Gas., 

 42, p. 329. 



MENDELISM AND INTERSPECIFIC HYBRIDS 



The complications of modern Mendelism have greatly in- 

 creased the difficulty of discussing the practical applications of 

 heredity. The word Mendelism itself has two essentially different 

 meanings that are beinu' used indiscriminately. A particular 

 form of alternative inheritance is called Mendelism and the same 

 name is applied to a general theory of heredity. It is true that 

 the Mendelian theory was suggested by the Mendelian form of 

 inheritance, but the facts are also capable of other interpreta- 

 tions. Many of the proposed applications of Mendelism to breed- 

 ing and eugenics are in reality only inferences from the theory 

 and are not in real accord with the facts on which they are sup- 

 posed to be based. 



An example of such a discrepancy may be found in the Ameri- 

 can Naturalist for July, 1912, in a paper entitled: "Evidence 

 of Alternative Inheritance in the F 2 Generation from Crosses of 

 Bos indicus on Bos taunts." Though readers are evidently ex- 

 pected to believe that the hybrids are showing a typical Men-, 

 delian inheritance of the contrasted parental characters, the facts 

 stated in the paper show that the behavior of the hybrids is not 

 in accord with the Mendelian theory of heredity. Alternative in- 

 heritance is manifested in these bovine hybrids, but it is not the 

 Mendelian form of alternative inheritance, with the contrasted 

 parental characters behaving as independent units combined by 

 the laws of chance. Instead of showing a Mendelian freedom of 

 combination of the contrasted characters, these hybrids afford a 

 much better illustration of a different principle of heredity, the 

 coherence of characters derived from the same parental stock. 



As the paper by Dr. Nabours seems to represent the only at- 

 tempt that has been made to give a scientific account of a unique 

 series of hybrids, it would be very undesirable to have the general 

 conclusion regarding the application of Mendelism accepted 

 without challenge. In addition to the scientific questions in- 

 volved, the importance of finding the best way of securing a full 

 utilization of the tick-resistant Brahma cattle in Texas will ap- 

 peal to all who have had the pleasure of seeing Mr. Borden 's im- 

 ported animals and their hybrid offspring. But practical recom- 

 mendations are hardly in order until the facts are better under- 



