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THE ZOOLOGIST. 



subject in earnest. The matter is now rendered of still greater 

 interest and importance through the publication of Prof. Loffler's 

 highly-valuable observations on the bacillus of what he calls 

 " mouse-typhus," by means of which he was enabled to put an 

 end, with astonishing success, to a plague of Voles (Arvicola, 

 savii?) which was devastating Thessaly in the spring of the 

 present year.* 



That the almost complete periodic extermination of the 

 Rabbits in the Canadian North-West is due to some virulently- 

 infectious epidemic disease which develops itself periodically, 

 there seems no reasonable room to doubt. There is equally 

 little doubt that careful study would reveal the bacillus or germ 

 of this disease, and that this bacillus would be capable of being 

 transported to Australia, and of being successfully communicated 

 to the rabbits there, when it is probable that results would 

 follow precisely similar to those now commonly observed in 

 Canada. 



It is true the American rabbit is not identical with the 

 common English rabbit, Lepus cuniculus, which is the too 

 abundant rabbit of Australasia ; but the two species are so nearly 

 identical that it is probable that a disease which kills one would 

 be equally fatal to the other, especially as evidence quoted here- 

 after shows that at least four other species of American rabbit 

 are periodically exterminated by the same, or a similar, epi- 

 demic. 



This almost complete periodical disappearance of the rabbits 

 in North-West Canada has by no means been overlooked by 

 scientific observers who have travelled through the country. 

 The earliest traveller who makes any reference to the matter is 

 Sir John Richardson, who, in his 'Fauna Boreali-Americana' 

 (London, 1829-37, p. 217), says of Lepus americanus : — 



"This is a common animal in the wooded districts of North America, 

 from one extremity of the continent to the other. It abounds on Mackenzie's 



River, as high as the 68th parallel of latitude It has numerous 



enemies, such as wolves, foxes, wolverines, martens, ermines, snow owls, 

 and various hawks; but the Canada Lynx is the animal which perhaps 



* For a translation of the Professor's remarks, see ' The Zoologist ' for 

 1892, pp. 297 — 328. In justice to myself, I may explain that the whole of 

 this article (with the oxception of a few remarks I have now added near the 

 end) was written years before the appearance of Prof. Loffler's observations. 



