Introductory 



he* dependent upon whether the animals live in herds or merely consort 

 in pairs. 



Less common is a gland situated on the inner surface of the hock, which 

 is anatomically equivalent to the ankle, or tarsus, of other animals. Hence 

 this gland and its tuft are termed the tarsal gland and tuft ; its position 

 being well shown in the coloured plate of the reindeer, where it stands out 

 in conspicuous whiteness from the dark colour of the rest of the limb. 



Lastly, the musks are peculiar in the possession by the males of a large 

 glandular pouch situated on the abdomen, and secreting the substance from 

 which these animals take their name. 



As non-scientific persons frequently have very hazy ideas as to the 

 nature and function of glands (which in truth are not fully known even to 

 the scientific), the following extract on this subject, taken from Sir William 

 Flower's above-mentioned article on the " Mammalia," may be quoted in 

 extenso. " Most mammals," writes Sir William, " have special glands 

 situated in modified portions of the integument, often involuted to form a 

 shallow recess or a deep sac with a narrow opening, situated in various 

 parts of the surface of the body, and secreting odorous substances, by the 

 aid of which individuals appear to recognise one another, and probably 

 affording the principal means by which wild animals are able to become 

 aware of the presence of other members of the species, even at great 

 distances. Although the commencement of the modifications of portions 

 of the external covering for the formation of special secretions may be at 

 present difficult to understand, the principle of natural selection will readily 

 explain how such organs become fixed and gradually increase in develop- 

 ment in any species, especially as there would probably be a corresponding 

 modification and increased sensibility of the olfactory organs. Such in- 

 dividuals as by the intensity and peculiarity of their scent had greater power 

 of attracting the opposite sex would certainly be those most likely to leave 

 descendants to inherit, and in their turn propagate, the modification." 



Classification. — Very different views as to the best way of classifying the 

 members of the Cervida? have obtained, and still obtain, among systematists ; 

 and the question, like others of a similar nature, depends largely upon the 

 individual bias of the particular writer. To some minds a system appears 

 to be more lucid when a number of divisions, based upon more or less 

 trivial characters, are adopted ; while to others greater clearness is obtained 



