608 GENETICS IN RELATION TO AGRICULTURE 



For after all in spite of our present dearth of detailed knowledge of 

 heredity in domestic animals there is no real cause for discouragement. 

 It is not yet two decades since the rediscovery of Mendel's law of heredity ; 

 and the most rapid progress has been made within the last five years. 

 It is not, therefore, at all strange that we have not yet obtained extended 

 data from experimental research; in fact, most of the Mendelian data 

 we now have on the larger domestic animals is of the interpretive kind, 

 that is, the conclusions have been drawn from records already in existence. 

 Experimental research such as has been employed in the study of the 

 inheritance of coat color in rodents, has not yet been carried out to 

 determine the relations of the various coat colors and patterns in horses 

 and cattle; the best that has been found possible thus far is the study of 

 herdbook records and breeders' notes. 



The Need of Research. Students know too well how difficult it is 

 to make due allowances for all the variable factors which may enter into 

 a given body of data. Consequently, however simple the conditions 

 may be, those conclusions which are based on records as crude as those of 

 herd books and breeders' notes are subject to a great deal of uncertainty. 

 Moreover, it is usually impossible under practical conditions to find 

 matings which have been carried out in such a way as to give crucial 

 tests of a given hypothesis of factor relations. We have emphasized this 

 difficulty in the discussion of Mendelian inheritance in domestic animals, 

 pointing out that very often alternative interpretations could be made of 

 the crude data extant; interpretations which could be very easily sub- 

 jected to a crucial test in the case of accurate scientific research. In the 

 domestic animals, as in Drosophila, the ideal goal of genetic analysis 

 should be that which determines accurately the mode of inheritance 

 and expression of as many Mendelian factors as is possible. The task 

 is difficult, but the increasing knowledge of heredity in lower forms will 

 immensely simplify its execution. 



The time and expense necessary for carrying out studies of heredity 

 has often deterred investigators from attacking problems in higher 

 animals because the possibility of economic application of the results 

 has seemed to be remote or almost certainly nil. But this is not the 

 point at issue, as may be clearly seen when the interrelations between 

 factors are considered. Accurate determination, for example, of the 

 various factors and factor interactions in the heredity of coat color in 

 cattle would give a secure and definite basis from which to prosecute other 

 investigations more intimately concerned with problems of economic im- 

 portance. It is even highly justifiable to commend such investigations, 

 because the problem is then first approached in its simplest form. There 

 is grave question as to the advisability of plunging pell mell into difficult 

 problems before the simpler ones have been solved, were it not for the 



