LAW OF VARIATION. 59 



to induce the most vigorous condition possible. Of 

 this, too, we have proof in the phenomenon sometimes 

 observed by breeders, that a strong mental impression 

 made upon the female by a particular male, will give 

 the ofifspring a resemblance to him, even though she 

 have no sexual intercourse with him. Of this, Mr. 

 Boswell in his prize essay published in 1828, gives a 

 remarkable instance. He says that Mr. Mustard of 

 Angus, one of the most intelligent breeders he had ever 

 met with, told him that one of his cows chanced to 

 come into season while pasturing on a field bounded 

 by that of one of his neighbors, out of which field an ox 

 jumped and went with the cow until she was brought 

 home to the bull. The ox was white, with black spots, 

 and horned. Mr. Mustard had not a horned beast in 

 his possession, nor one with any white on it. Never- 

 theless, the produce of the following spring was a black 

 and white calf with horns. 



The case of Jacob is oiten quoted in support of this 

 view, and although many believe some miraculous 

 agency to have been exerted in his case, and though 

 he could say with truth, " God hath taken away the 

 cattle of your father and given them to me," it seems, 

 on the whole, more probable, inasmuch as supernatural 

 agency may never be presumed, except where we know, 

 or have good reason to believe, that natural causes are 



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