The Dying Fluanaco. 229 
coming home to be relieved from his sufferings, but 
the motive is the same in both cases; at the gate 
the only pain the animal has ever experienced has 
invariably begun, and there it has ended, and when 
the spur of some new pain afflicts him—new and yet 
like the old—it is to the well-remembered hated 
gate that it urges him. 
To return to the huanaco. After tracing the 
dying instinct back to its hypothetical origim— 
namely, a habit acquired by the anima] in some 
past period of seeking refuge from some kind of pain 
and danger at a certain spot, it is only natural to 
speculate a little further as to the nature of that 
danger and of the conditions the animal existed in. 
If the huanaco is as old on the earth as its 
antique generalized form have led naturalists to 
suppose, we can well believe that it has survived 
not only a great many lost mammalan types, but 
many changes in the conditions of its life. Let us 
then imagine that at some remote period a change 
took place in the climate of Patagonia, and that it 
became colder and colder, owing to some cause af- 
fecting only that portion of the antarctic region ; 
such a cause, for instance, as a great accumulation 
of icebergs on the northern shores of the antarctic 
continent, extending century by century until a large 
portion of the now open sea became blocked up with 
solid ice. If the change was gradual and the snow 
became deeper each winter and lasted longer, an 
intelligent, gregarious, and exceedingly hardy and 
active animal like the huanaco, able to exist on the 
driest woody fibres, would stand the best chance of 
maintaining its existence in such altered conditions, 
