EBB AND FLOW OF ANIMAL LIFE 109 



The Muskrat's variation probably has relation chiefly 

 to the amount of water, which, as is well known, is 

 cyclic in the north-west. 



The general resemblance of Beaver and Otter lines 

 may not mean anything. If, as said, the Otter occa- 

 sionally preys on the Beaver, 

 these lines should in some de- 

 gree correspond. 



The Wolf line does not man- 

 ifest any special relationship 

 and seems to be in a class by 

 itself. The great destruction 

 from 1840 to 1870 was prob- 

 ably due to strychnine, newly 

 introduced about then. 



T 1 !^ "D^ TtnJ~ r^ Microtus pocket hole. Ed- 



Die Bear, Badger, and monton; May 10, 1907 



Wolverine go along with little 



variation. Probably the Coon does the same; the 

 enormous rise in 1867 from an average of 3,500 per 

 annum to 24,000 was most likely a result of accidental 

 accumulation and not representative of any special 

 abundance. Finally, each and every line manifests 

 extraordinary variability in the '30's. It is not to be 

 supposed that the population fluctuated so enormously 

 from one year to another, but rather that the facilities 

 for export were irregular. 



The case is further complicated by the fact that some 

 of the totals represent part of this year and part of 

 last ; nevertheless, upon the whole, the following gen- 

 eral principles are deducible: 



(a) The high points for each species are with fair 

 regularity 10 years apart. 



