Simpson: Coat-Pattern in Mammals 



335 



AN UNUSUAL HORSE BELT 



Bright bay mare with a seal brown belt encircling the body in the position where piebald 

 horses carry a white belt. The inheritance of this mutation was not tested further than 

 two colts that were normal. Photograph by Spillman and vSimpson. (Fig. 4.) 



Two hybrid belted-red sows, one with 

 belt on left side only, the other with 

 belt only on her right side, and each 

 devoid of white on opposite side where 

 it should be white, were each bred to a 

 pure Red-Tain worth male, causatively 

 for ascertaining the action of orienta- 

 tion in the first two cells of the blasto- 

 mere, and the polar localization of the 

 front and hinder ends of the lateral pair 

 of cells, to be determined b}^ the pattern 

 of their produce. To our surprise, in 

 the goodly number of young from each 

 sow there were no half -belts; and on 

 those having preponderance of belt on 

 one side, these did not correlate with 

 the unsymmetry of their dam as to same 

 side: for there were as many of right- 

 maximum from the left-belt sow, and 

 as many left -maximums from the right- 

 belt sow. There were too as many 

 perfect belts as from normal belt sows, 

 under Mendelian expectancy. This 



could be explained on the assumption 

 that the cytoplasm had effected pattern 

 proportion at the two-cell stage of the 

 unsymmetrical belts. If in the two-celled 

 stage of development these had sun- 

 dered, as is supposed in identical twins 

 of man, these one-side belts would have 

 each given phenomenon of "identical 

 twins," one of each belted, the mate 

 entirely selfed. I believe T. H. Morgan 

 has found vinegar-flies (Drosophila) 

 that had the right eye of one color and 

 the left of another, and the same has 

 been seen in man. We have, however, 

 other evidence, that the size of spots in 

 a pattern, and their location, is the 

 effect of a lineal family of chromosomes, 

 that at a fixed number of generations 

 from fertilization reach differentiation. 

 This is shown by paired anterior-poste- 

 rior markings ; and also by the fact that 

 when a spot is found on one side, its 

 mate at the same location may usually 



