518 GENETICS IN RELATION TO AGRICULTURE 
so that the hinny resembles the horse more than does the mule. There 
appears, however, to be some question about the explanation of this case, 
and it is a significant fact that Goldschmidt, who mentions common 
report in connection with this case, has seen fit to question the accuracy 
of it. Apparently many of the differences are due to individual differ- 
ences in the animals which have been used, and are, therefore, of no sig- 
nificance for determining differences in reciprocal crosses. 
The fertility of the mule is an everlasting question of dispute, for 
from time to time reports are made of fertile mare mules. Unquestion- 
ably such cases are very rare, and in most cases some doubt may be 
thrown either upon the question as to whether the mare “mule’’ was a 
Fre. 199.—The mare mule on the left. On the right, her foal by a jack. Note the resem- 
blance in markings of the leg. (After von Wahl.) 
mule at all, or whether, if a mule, she was not suckling the colt of some 
other dam, for there are abundant authentic instances of mare mules 
which have given milk. Among instances of fertile mules are those 
reported by von Wahl, who discovered two cases in Brazil of mules which 
had produced foals when bred to an ass. The foals were somewhat 
larger than their dams, and were throughout mule-like in appearance. 
Von Wahl reports, also, a case of a foal from a mare mule out of a stallion, 
but did not himself examine it. It is only fair to state that in these 
cases the chain of evidence is not complete. Lloyd-Jones has given a 
résumé of the evidence with respect to fertile mules, and has noted some 
new cases, all of which are, however, questionable. Mares apparently 
occasionally exhibit mule-like characters, and many of the cases reported 
appear to depend upon amistakeof such a mare fora mule. Figs. 199, 200 
and 201 seem to represent an instance of this kind. 
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