34 Farmers' Bulletin 1167. 



This theory was that the first male to impregnate a female perma- 

 nently endowed the female with his characters, so that subsequently 

 she would always exhibit them in her progeny. If this male was of 

 another breed the female became a crossbred by means of this first 

 impregnation. The Lord Morton mare was a Thoroughbred; she 

 was mated with a quagga and produced a hybrid foal. She was 

 then mated to a Thoroughbred stallion and produced a foal with 

 stripes. In spite of the fact that Darwin knew that frequently horses 

 had both shoulder stripes and leg stripes, and that mules with leg 

 stripes were known to occur, he coupled this Morton case with the 

 erroneous beliefs of dog breeders and gave the theory in question 

 the powerful support of his authority. The theory has been com- 

 pletely disproved by Ewart, who has clearly shown it to have been 



Purebred Poland China sow. 

 FIG. 29. Contrast this picture with the photograph of the Piney-Woods sow. 



a manifestation of inheritance. Horses, asses, and other equine stock 

 have a common origin. With our present knowledge of Mendel's law, 

 which was unknown to Darwin, we can understand much more readily 

 that the appearance of stripes in horse stock is more likely due to the 

 unexpected appearance of a recessive character than to any residu- 

 ary effect of any impregnation on the chromosomes of the female 

 germ cells. Such a theory is utterly impossible if we accept the 

 known facts regarding the chromosomes and their behavior. 7 



Crosses most readily demonstrate the operations of Mendelism, 

 and the more violent the cross the more astonishing are the results. 

 It often happens that the cross of ass and mare brings to the surface 

 characters common to the horse ancestors of the distant past. An- 

 other interesting case is seen in crossing certain breeds of hogs, re- 



7 See pages 5-8. 



