Lush: A Notch In Ears of Jersey Cattle 



13 



TWIN DAUGHTliRS OF GAMBOGE'S RALEIGH 



These heifers both have moderately notched ears. They appear to be identical twins, as they 

 are alike in all other respects as well. Identical twins are developed from a single fertilized egg 

 cell. Some investigators have concluded on statistical grounds that identical twins do not occur 

 in cattle, so that this case is of interest in disproving such a theory. (Fig. 12.) 



reached from a statistical study^ that 

 few or no identical twins are produced 

 in cattle. 



There is no intrinsic economic value 

 in this notch just as there is none in 

 the peculiar color markings of different 

 breeds, but it is possible that other 

 factors economically important, but 

 difficult and expensive to trace, such 

 as the factors for high milk and fat 

 production, may be linked quite closely 

 to the factor for the notch. The fact 

 that the first daughters of Gamboge's 

 Raleigh are showing up well at the 

 pail will give an opportunity of seeking 

 for linkage when more of them have 

 begun production. Of course, the 

 chances are against finding such link- 

 age, since there are nineteen pairs of 

 chromosomes in cattle,^ but if enough 

 of these non-economic characters are 

 investigated, a few will ultimately be 

 found which will serve as guides to the 

 inheritance of the more important ones. 



Finally, as we learn one by one in 



our breeds of livestock, of additional 

 characters that are transmitted like 

 those of Drosophila and other labora- 

 tory animals, the idea will be dispelled 

 that domestic animals are a law unto 

 themselves, untouched by the knowl- 

 edge gained from the study of insects 

 and rodents in genetics laboratories. 

 When as many cattle as Drosophila 

 shall have been examined carefully, 

 it is not unreasonable to expect that as 

 many hereditary factors will be dis- 

 covered in them. A knowledge of the 

 relations of large numbers of hereditary 

 factors will ultimately offer a broader 

 control of livestock breeding than a 

 specific knowledge of the transmission 

 of a few, irrespective of any practical 

 value of the latter at present. Progress 

 in livestock breeding in the near future 

 will depend as much on the study of all 

 classes of characters, regardless of wheth- 

 er they are economic or non-economic, as 

 on an intensive study concentrated on 

 one or two particularly valuable traits. 



3 Gowen, John W. 1922, "Identical Twins in Cattle?" Biol. Bull. Vol. 42, No. 1. 

 * Wodsedalek, J. E., 1920, "Studies on the Cells of Cattle with Especial Reference to Spermat- 

 ogenesis, Oogonia and Sex-Determination." Biol, Bull. Vol. 38, No. 5. 



