,g,,. NOTES AND COMMENTS. 729 



Rabbits. 



Mr, Miller Christy, in a communication " On the Extermination 

 of the Rabbit in Australasia" (Zoo/oo'/si', Nov.), refers to the remarkable 

 periodical variation in numbers exhibited by the Lepus americanus in the 

 Canadian North- West. He says that for several years in succession 

 the animal becomes so scarce as to be quite difficult to obtain, 

 increasing in the next few years to so extraordinary an extent as to 

 become the most abundant mammal in the country. After the 

 maximum of increase has been attained, the rabbits commence to die 

 off, and, before many weeks are over, their dead bodies strew the 

 woods in all directions, while a live rabbit is scarcely to be met with. 

 Mr. Christy agrees with Sir John Richardson (1837) that the disap- 

 pearance is due to an epidemic comparable to the "mouse-typhus" 

 of Loffler. Professor Hind (i860) thought exhaustion following a 

 severe winter accounted for the fact. But the numerous extracts Mr. 

 Christy quotes from many writers who have paid attention to the 

 subject, and more especially a brief newspaper paragraph which 

 professes to diagnose the cases — swollen throat, follow^ed by diarrhoea 

 and death — seem to prove that the disappearance of the rabbits is 

 due to disease. If this be so, and if the bacteriologists can find 

 some virulent disease peculiar to the rabbit, by all means let experi- 

 ments be tried for the wholesale extermination of the pest in Australia, 

 where, judging from all accounts, the second source of the wealth 

 of the colony, the sheep farm, is rapidly becoming a thing of the 

 past. 



Fossil Rhinoceroses. 



In a recent memoir published in the Bull. Soc. Imp. Nat. Moscoii 

 (vol. vi., pp. 146-231, pis. iii.-v.), Madame M. Pavlow continues 

 her elaborate researches on the phylogeny of the Ungulates, treating, 

 in this fasciculus, first of the fossil Rhinoceroses of Russia, and then 

 of the mutual relationships of all the members of the family. The 

 species found in Russia are comparatively few, and as they are all 

 identical with Western European forms, call for no particular remark. 



In treating of the phylogeny of the family, the authoress publishes 

 a genealogical table, in which the whole of the Rhinoceroses, both 

 fossil and extinct, are derived from the genus Systemodon of the Lower 

 Eocene of North America. That such a characteristically Old World 

 group should have had a Transatlantic origin appears startling, 

 although it is paralleled in the case of the Camels : and we are not 

 at present prepared to admit that the case is proved. Madame 

 Pavlow's genealogical table is open to a considerable amount of 

 criticism, but since Professor H. F. Osborn informs us that he is at 

 present engaged on working out th.e phylogeny of this group, we think 

 it better to defer such criticism until his memoir shall have appeared. 

 We may state, however, that in attempting to trace the origin of the 



