THE GLANDS. 249 



wanting. In this regard he is precisely like our moose, so we 

 must dispense with his fourth section. 



We may briefly summarize these sections thus : First., where 

 the outside tuft is present and the inside wanting, Second, where 

 both are present, and Third., where the inside tuft is present and 

 that on the outside wanting. This certainly divides the genus 

 into very natural sections easily recognized. 



By a careful study of these tufts of liair and tlie structures 

 which they indicate and cover, I find we are enabled with equal 

 certainty to subdivide these sections and designate the species 

 composing them respectively. Dissection, with aid of the micro- 

 scope, shows ns that each of these tufts of hair indicates the place 

 of, and covers and surrounds a cutaneoiis gland, a distinct organ 

 which in the economy of the animal has its proper and peculiar 

 functions to perform. When we find such an organ present in 

 one class of animals, and absent in another class sufficiently re- 

 sembling them to be ranked in the same genus, we are almost 

 prepared to declare them to be specifically different, and are led 

 at once to look for other difference to corroborate the suspicion. 

 A distinct member, always constant in all its features, among all 

 the individuals of a class who freely associate together, wherever 

 such association is permitted without restraint, and who avoid 

 the society of all other similar animals destitute of that member, 

 — this peculiarity adds to the suspicion of a specific difference ; 

 and so on, whenever we can find differences either in structure 

 or habit which cannot be assigned to accidental or factitious cir- 

 cumstances or surroundings, such as climate, altitude, aliment, 

 and the like, we are more and more inclined to draw the dividing 

 line of species. But whenever we can ascribe peculiarities either 

 of structure or habit to such accidental surroundings, we may 

 conclude that the differences would gradually disappear on a 

 change of circumstances ; then we may be justified in the opinion 

 that the change is transient and we liave but a variety. 



I know of no feature or member of any of these a-nimals so 

 exactly alike, in dimensions, location, coloring, and structure, on 

 every individual of each species of our deer, as these tufts of 

 hair and tlie glands which they conceal, and yet those on the 

 outside of the metatarsus are entirely different from each other 

 on the different species, and this difference is so great that when 

 one's attention is once called to them the most casual observation 

 is sufficient to identify them, and enable us to say, with certainty, 

 to which species they belong. We look in vain for any other 



