being well known instances. In different continents or countries far 

 separated, the faunas and floras are usually radically different, being 

 derived from different stocks ; but in them all successive climatic 

 zones of life will be experienced in passing in a general north or 

 south direction. 



A careful study of the breeding ranges of the birds of Eastern 

 North America has clearly demonstrated this as regards our con- 

 tinent. The northern and southern limits of the breeding ranges of 

 the various species fall along certain more or less distinct lines, 

 where there are likewise decided changes in the flora as well as in 

 the climate and general character of the country. In this manner 

 the continent may be separated into several parallel zones, each of 

 which marks the northern and southern limit of the breeding range 

 of certain species. 



Besides the Tropical Realm which reaches the coast of southern 

 Florida, and the circumpolar Arctic Realm, five life zones are clearly 

 marked in eastern North America. These are known as the (1) 

 Louisianian, (2) Carolinian, (3) Alleghanian, (4) Canadian, (5) Hud- 

 sonian. Now it must not be supposed that the boundaries of these 

 zones compare in any way with the regularity of the parallels of 

 latitude, for they are, on the contrary, exceedingly broken and ir- 

 regular. This is of course due to the topography of tlie country, as 

 the elevated mountain ranges and plateaus, having of necessity a 

 cooler climate than the surrounding lowlands, carry a more northern 

 fauna and flora far southward, while on the other hand low open river 

 valleys are always milder in climate, and thus furnish avenues by 

 which the southern animals and plants extend their distribution 

 northward. We therefore find the boundaries of these " life zones " 

 extending up and down in a zig-zag manner as they follow the vary- 

 ing irregularities of the land. These irregularities of surface fre- 

 quently make the lines of separation between one zone and another 

 all .the more strongly marked, since on the precipitous side of a 

 mountain the change of climate as one ascends is much more rapid 

 than is experienced in traveling northward on the level. The 

 change in the vegetation is similarly sudden, the line between the 

 coniferous and deciduous forests being usually quite apparent, and 

 with the change in vegetation comes a corresponding change in the 

 birds and other animals. 



Of the four life zones already mentioned, three pass through 

 Pennsylvania and New Jersey. The Carolinian Zone occupies the 



