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 



i 



Fia. 199. The mare mule on the left. On the right, her foal by a jack, 

 blance in markings of the leg. (After von Wahl.) 



Note the resem- 



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 

 r6sum6 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 a mistake of such a mare for a mule. Figs. 199, 200 

 and 201 seem to represent an instance of this kind. 



