74 FROM AN EASY CHAIR 



of bubonic plague. To the naturalist it means a group 

 or natural cohort of small mammals similar to our 

 common rat and mouse, representatives of which are 

 found in every quarter of the globe and in almost 

 every island of the sea. The distinct "kinds 11 or 

 " species " are numbered by the hundred. They are 

 extraordinarily alike, and can only be distinguished 

 and classified into proper " species " by careful examina- 

 tion and measurement. Mr. Oldfield Thomas, of the 

 Natural History Museum, has made a special study 

 of them. To give an idea of his work, it may be 

 mentioned that ninety different names had been given 

 by previous writers to as many apparently distinct 

 kinds of rat occurring in India. But by careful 

 measurement and study of the relations to one another 

 of these rats, Mr. Thomas has reduced the number of 

 really distinct Indian species of rats and mice (for a 

 mouse is only a smaller rat) to nineteen. What we 

 call in English water-rats, or water-voles, field-voles, 

 and such little foreign beasts as the lemming and the 

 hamster, are very close to rats in appearance, but are 

 separated on account of clear differences of structure 

 from true rats and mice. 



At a meeting in London the total destruction of 

 " rats " was advocated. Whether it was affirmed at the 

 meeting, or was merely an error of those who wrote and 

 commented on the matter afterwards, I do not know, 

 but it was very generally stated in this connection that 

 the old Black rat (known to naturalists as Mus rattus) 

 is quite extinct in England, and that its place has been 

 taken by the Norwegian, or Grey rat (Mus decumanus), 

 also called the Hanoverian rat, because it became 

 noticeable by its abundance in this country at the 

 time of the accession of the Hanoverian kings. The 

 Black rat is not extinct in England, not even very rare. 

 Mr. Stendall lately sent me specimens caught in his ware- 

 house in the City of London, where they are abundant. 



