5 2 MAMMALIA. 



out brown."* On this point Dr. Coues writes as follows: "The 

 question practically narrows to this : Is the change coincident with 

 renewal of the coat, or is it independent of this, or may it occur in 

 both ways ? Specimens before me prove the last statement. Some 

 among them, notably those taken in spring, show the long woolly 

 white coat of winter in most places, and in others present patches 

 generally a streak along the back of shorter, coarser, thinner hair, 

 evidently of the new spring coat, wholly dark brown. Other speci- 

 mens, notably autumnal ones, demonstrate the turning to white of 

 existing hairs, these being white at the roots for a varying distance, 

 and tipped with brown. These are simple facts not open to question. 

 We may safely conclude that if the requisite temperature be ex- 

 perienced at the periods of renewal of the coat, the new hairs will 

 come out of the opposite color; it not, they will appear of the same 

 color, and afterwards change; that is, the change may or may not be 

 coincident with shedding. That it ordinarily is not so coincident 

 seems shown by the greater number of specimens in which we ob- 

 serve white hairs brown-tipped. As Mr. Bell contends, temperature 

 is the immediate controlling agent. This is amply proven in the fact 

 that the northern animals always change; that in those from inter- 

 mediate latitudes the change is incomplete, while those from farther 

 south do not change at all."f 



Dr. Coues, it will be observed, states, without qualification, that 

 "temperature is the immediate controlling agent" in this change of 

 color, and remarks : " This is amply proven in the fact that the 

 northern animals always change," etc. Now the facts with which I 

 am familiar lead me to take a very different view of the case, and I 

 am of opinion that temperature, per se, has very little to do, either 

 with the time of the change, or the fact of the change; and in sup- 

 port of this view I adduce the following facts and let it be under- 

 stood that my observations pertain to the species as found in the 



* Quadrupeds of North America, Vol. II, 1851, pp. 62-63. 

 | Fur-bearing Animals, 1877, p. 123. 



