A SHOT AT A MOUNTAIN SHEEP 187 



for ourselves, we applied them loosely. The ordinary 

 deer is sometimes known as the red deer, sometimes as 

 the Virginia deer, and sometimes as the whitetail deer 

 the last being by far the best and most distinctive term. 



In the present condition of zoological research it is 

 not possible to state accurately how many " species " of 

 deer and sheep there are in North America, both because 

 mammalogists have not at hand a sufficient amount of 

 material in the way of large series of specimens from dif- 

 ferent localities, and because they are not agreed among 

 themselves as to the value of " species," or indeed as to 

 exactly what is denoted by- the term. Of course, if we 

 had a complete series of specimens of extinct and fossil 

 deer before us, there would be a perfect intergradation 

 among all the existing forms through their long-vanished 

 ancestral types, as the existing gaps have been created by 

 the extinction and transformation of those former types. 

 Where the gap is very broad and well marked no dif- 

 ficulty exists in using terms which shall express the dif- 

 ference. Thus the gap separating the moose, the caribou, 

 and the wapiti from one another, and from the smaller 

 American deer, is so wide, and there is so complete a lack 

 of transitional forms, that the differences among them are 

 expressed by naturalists by the use of different generic 

 terms. The gap between the whitetail and the different 

 forms of blacktail, though much less, is also clearly 

 marked. But when we come to consider the blacktail 

 among themselves, we find two very distinct types which 

 yet show a certain tendency to intergrade; and with the 

 whitetail very wide differences exist, even in the United 



