47 4 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



i. e., a region of palms at the base, a region of hard- wood 

 trees higher up, then a region of pines, a treeless region, 

 and a plantless region or perpetual snow. In the sierra, 

 which is in the temperate zone, the region of palms is 

 wanting, but all the others are present. To two thou- 

 sand feet or more hard-wood trees predominate, then 

 pines and spruces up to ten thousand to twelve thousand, 

 then shrubs and flowers, and finally perpetual snow. 



Zoological Temperature Regions.— Thus far 

 we have spoken only of plants, because their relations 

 are more simple and easily brought out on account of 

 their being fixed to the soil. But the same laws govern 

 animal species also. Animals also have their tempera- 

 ture regions. For example, the great cats, the hyenas, 

 the great pachyderms, the camels, the ostriches, parrots, 

 toucans, the reef-building corals, etc., are tropical, while 

 the polar bear, the civets, martens, seals, walruses, and 

 whales are predominantly arctic. 



COMPLETER DEFINITION OF TEMPERATURE REGIONS. 



i. The range of any organic form is the extent or 

 area of its distribution. It is most restricted for spe- 

 cies; is greater for genera, because when a species 

 ceases the genus may be continued by other species of 

 the same genus. It is still greater for families, because 

 when a genus ceases the family may still continue as 

 other genera of the same family, etc. The range is ex- 

 tensive in proportion to the largeness of the taxonomic 

 group. For example, we have said that the range of 

 the conifers in the sierra was from two thousand to ten 

 thousand feet. This is the range of the order, but no 

 species extend so far. If we take the genus Pinus we 

 have first the digger pine {P. sabiniana), then the yellow 

 pine {P. ponderosa), then the sugar pine {P. Lamberti- 



