192 THE TOWER MENAGERIE. 
their horns, which are formed of an elastic sheath en- 
closing a solid nucleus, and are for the most part com- 
mon to the females as well as to the males. They have 
no canine teeth, and exhibit no appearance of a beard 
such as is seen in the Goats. The horns vary greatly in 
the different races; they are sometimes straight and 
upright, at other times slightly curved, and frequently 
spirally twisted with the most beautiful regularity: they 
are usually surrounded by elevated rings or by a spiral 
ridge, are constantly of the same form in the same 
species, and are not subject to an annual falling off and 
renewal, as in the Deer, from which they differ also in 
their mode of growth, the horns of the latter group 
lengthening at their apices, while those of the former 
receive their increase at the base. 
In their natural habits the numerous species of which 
this group is composed approach very closely to the 
Deer; there is, however, considerable variety in their 
mode of life. They inhabit almost every description of 
country; the sandy desert, the open plain, the thicket, 
the forest, the mountain, and the precipice, being, each 
in its turn, the favourite haunt of the different races ; 
but, with the exception of a few species, they do not 
advance much beyond the limits of the tropics. The 
smaller ones usually prefer a solitary life, but the 
larger, for the most part, congregate together in herds, 
which are generally few in number. In their manners 
they exhibit much of that cautious vigilance and easily 
startled timidity, combined with a certain degree of 
occasional boldness and not a little curiosity, which are 
the natural consequences of their wild and unrestricted 
habits, of their trivial means of defence against the 
