566 GENETICS IN RELATION TO AGRICULTURE 
The strength of the evidence in this case can be understood better by 
reference to Fig. 221, which shows the male quagga which Lord Morton 
used in his experiments, the hybrid which was produced by the chestnut 
Arabian mare when bred to this quagga, and the filly which she produced 
subsequently to the service of a purebred black Arabian stallion. 
Fig, 221.—Lord Morton’s male quagga, a hybrid between a Chestnut Arabian mare 
and this quagga, and a filly produced subsequently by the same mare when mated to a 
pure-bred black Arabian stallion. (After Ewart.) 
But although many scientists have granted the weight of this evidence, 
later scientific thought has questioned strongly even the possibility of 
such effect of the male upon the female. Accordingly many adverse 
criticisms have been made against the validity of this case, some of which, 
as for example that of J. Wilson, go so far as to deny the hybrid origin of 
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