134 STERILITY FROM Chap. XYII1. 



judge, says, " it is remarkable that lions breed more freely in 

 " travelling collections than in the Zoological Gardens ; probably 

 " the constant excitement and irritation produced by moving from 

 " place to place, or change of air, may have considerable influence 

 " in the matter." 



Many members of the Dog family breed readily when confined 

 The Dhole is one of the most untamable animals in India, yet ; 

 pair kept there by Dr. Falconer produced young. Foxes, on the 

 other hand, rarely breed, and I have never heard of such an occur- 

 rence with the European fox: the silver fox of North America 

 (( anis argentatus), however, has bred several times in the Zoo- 

 logical Gardens. Even the otter has bred there. Every one 

 knows how readily the semi-domesticated ferret breeds, though 

 shut up in miserably small cages ; but other species of Yiverra and 

 Paradoxurus absolutely refuse to breed in the Zoological Gardens. 

 The Genetta has bred both here and in the Jardin des Plantes, and 

 produced hybrids. The Herpestes fasciutus has likewise bred ; but I 

 was formerly assured that the H. griseus, though many were kept 

 in the Gardens, never bred. 



The Plantigrade Carnivora breed under confinement much less 

 freely than other Carnivora, although no reason can be assigned 

 for this fact. In the nine-year Eeport it is stated that the bears 

 had been seen in the Zoological Gardens to couple freely, but 

 previously to 1848 had most rarely conceived. In the Beports 

 published since this date three species have produced young 

 (hybrids in one case), and, wonderful to relate, the white Polar 

 bear has produced young. The badger (Heles taxus) has bred 

 several times in the Gardens ; but I have not heard of this occurring 

 elsewhere in England, and the event must be very rare, for an 

 instance in Germany has been thought worth recording. 19 In 

 Paraguay the native Nasua, though kept in pairs during many 

 years and perfectly tamed, has never been known, according to 

 Eengger, to breed or show any sexual passion; nor, as I hear from 

 Mr. Bates, does this animal, or the Cercoleptes, breed in Amazonia. 

 Two other plantigrade genera, Procyon and Gulo, though often 

 kept tame in Paraguay, never breed there. In the Zoological 

 Gardens species of Nasua and Procyon have been seen to couple ; 

 but they did not produce young. 



As domesticated rabbits, guinea-pigs, and white mice breed 

 so abundantly when closely confined under various climates, it 

 might have been thought that most other members of the Rodent 

 order would have bred in captivity, but this is not the case. 

 It deserves notice, as showing how the capacity to breed sometimes 

 goes by affinity, that the one native rodent of Paraguay, which 

 there breeds freely and has yielded successive generations, is the 

 Cavia apera ; and this animal is so closely allied to the guinea-pig, 



19 Wiegmann's ' Archiv fur Xaturgesch.,' 1837, s. 162. 



