150 PHILOSOPHY OF ZOOLOGY. 



These instances of monstrosity, as they occur but sel- 

 dom, and chiefly in domesticated animals, present few ob- 

 stacles to their systematical arrangement. It is frequently, 

 however, a matter of considerable difficulty to determine 

 the sexes at an early age, and the young from mature in- 

 dividuals of the same species. 



B. Varieties. — Although the vital principle of every ani- 

 mal is restrained, in all its operations, within certain limits, 

 peculiar to each species, these are not so very confined as 

 to prevent slight alterations of character from taking place, 

 without disturbing the harmony of the whole. 



Individuals of the same species, living in a wild state, 

 and exposed alike to the same physical circumstances, rare- 

 ly exhibit variations of character to any extent. When, 

 however, the individuals of the same species are compelled 

 to live in different countries, they are not placed in the same 

 physical circumstances. Constitutional efforts will be made 

 by each of these groups, to accommodate themselves to the 

 conditions of their station, and these will display themselves 

 in variations of colour, size, and even the form of certain 

 parts. 



As domestication subjects animals to the greatest variety 

 of changes in their physical circumstances, so it operates 

 most powerfully in the production of varieties. These 

 take place in obedience to the tendency to accommodation, 

 or redundant parts are produced in consequence of excess 

 of nourishment. 



Many of these variations are peculiar to individuals, 

 while others are permanent, and capable of being transmit- 

 ted to the off'spring. These permanent varieties in the 

 human species, now generally limited to five, the Cau- 

 cassian, Mongolian, Ethiopian, American, and Malay, 

 have given rise to the belief, that there are several species 



