358 COMPARATIVE ZOOLOGY. 
‘Great fleas have little fleas and smaller fleas to bite ’em ; 
And these again have other fleas, and so ad infinitum.” 
Thus the ocean of life is inexhaustible. It spreads in 
every direction, into time past and present, flowing every- 
where, eagerly surging into every nook and corner of cre- 
ation. On the mountain-top, in the abysses of the Atlan- 
tic, in the deepest crevice of the earth’s crust, we find 
traces of animal life. Nature is prodigal of space, but 
economical in filling it.” 
Animals are distributed over the globe according to 
definite laws, and with remarkable regularity. 
Each of the three great provinces, Earth, Air, and Wa- 
ter, as also every continent, contains representatives of all 
the classes; but the various classes are unequally repre- 
sented. Every great climatal region contains some species 
not found elsewhere, to the exclusion of some other forms. 
Every grand division of the globe, whether of land or 
sea, each zone of climate and altitude, has its own fauna. 
And, in spite of the many causes tending to disperse ani- 
mals beyond their natural limits, each country preserves 
its peculiar zoological physiognomy. 
The space occupied by the different groups of animals 
is inversely as the size of the individuals. Compare the 
Coral and Elephant. 
Fauna now occupying a separate area is closely allied 
to the fauna which existed in geologic times. Thus, Aus- 
tralia has always been the home of Marsupials, and South 
America of Edentates. 
It is a general rule that groups of distinct species are 
circumscribed within definite, and often narrow, limits. 
Man is the only cosmopolitan; yet even he comprises sev- 
eral marked races, whose distribution corresponds with the 
great zoological regions. ‘The natives of Australia are as 
grotesque as the animals. Oertain brutes likewise have a 
great range: thus, the Puma ranges from Canada to Pata- 
