INHERITANCE OF ACQUIRED CHARACTERS 171 



resemble a previous jack sire would be quickly observed. 

 The writer l and C. B. Hutchison made an investigation 

 of a large number of the horse offspring of mares which 

 had previously foaled mule progeny from jack sires. 

 Many of the horse foals examined were from mares that 

 had produced more than one mule. In one case a mare 

 had given birth to thirteen mule foals in succession and 

 had then produced a horse foal. Many similar cases 

 gave opportunity to observe a number of examples in 

 connection with which full and favorable opportunity 

 was present for the display of the influence of a previous 

 impregnation. If, as some believe, the influence of a 

 previous impregnation is cumulative and the dam becomes 

 more and more completely infected by successive matings, 

 these results should give an excellent opportunity to 

 obtain some evidence on the theory of " infection " or 

 " saturation.' 1 



A total of 168 mares were located that had given birth 

 to mule foals and later had produced horse foals. Of 

 this number 108 produced their first foal to a jack and 

 later gave birth to horse foals. Among the number were 

 forty mares that produced their first foals to a stallion, 

 later producing mule foals and then again horse foals. 

 The remainder were bred in a somewhat irregular manner, 

 but all were alike in having produced horse foals following 

 mule foals. The number of mares producing one or more 

 mule foals each followed in every case by horse foals was 

 as follows : Eighteen males produced one mule foal each, 

 followed by a horse foal ; twenty-two mares produced 

 two mule foals each, followed by a horse foal; twelve 

 mares produced three mule foals each, followed by a 



1 Mumford and Hutchison, Unpublished Data of the Missouri 

 Experiment Station. 



