VARIETY AND UNITY IX LIFE 



15 



record of each year we find about twelve thousand species, about 

 three times as many animals as in the whole " Systema Naturae." 

 Yet the field shows no signs of exhaustion. As the volumes of 

 the " Zoological Record " stand on the shelves, it is easy to see 

 that the later volumes are the thickest; and those of the new 

 century, with a general revival of interest in systematic zoology 



U: 



FIG. 4. California quail, Lophortyx californicus. (Two-thirds natural size.) 



and the study of geographical distribution, are the thickest of 

 all. The depths of the sea, the jungles of the tropics, the crev- 

 ices of the coral reefs, the tundras of the north, the limbs of 



