CONCLUDING OBSERVATIONS. 363 
The marine animals, as a whole, are equally superior to 
those of other regions; the seas teem with Crustaceans 
and numerous Cephalopods, together with an infinite va- 
riety of Gasteropods and Acephala. The Echinoderms 
there attain a magnitude and variety elsewhere unknown; 
and, lastly, the Polypes there display an activity of which 
the other zones present no example. Whole groups of 
islands are surrounded with coral reefs formed by these 
little animals.” 
632. This variety is made more striking by the fact 
that each continent has many animals in its tropical re- 
gion peculiar to itself. Thus the Giraffe and Hippopota- 
mus appear only in Africa} and that strange animal, the 
Sloth, is found only in America. The 300 species of Hum- 
ming-birds are exclusively American, nearly all of them 
being tropical. The Sunbirds, on the other hand, which 
are somewhat like them, do not appear at all in America, 
but are widely scattered over Asia, Africa, and the isl- 
ands of the Pacific. 
633. Some of the local Faunas have prominent pecul- 
iarities. The Fauna of Brazil is exceedingly rich, with 
its gigantic Reptiles, its Monkeys, its Edentata, its bril- 
liant Humming-birds, and its wonderful variety of insects. 
There is no part of the world that has so peculiar a Fauna 
as Australia. Here are great numbers of Marsupial ani- 
mals. Here, also, is that strange animal, the Duck-billed 
Platypus (§ 133); and here, too, is the Black Swan, sup- 
posed to be an impossibility till it was found in that sin- 
gular country. 
634. The pupil has by no means obtained an adequate 
idea of the abundance and variety of the animal kingdom 
from what he has seen in this book of its different depart- 
ments. In so small a space only a few specimens of each 
group could come under consideration. That you may 
have some idea of the extent of the field which zoology 
has opened, [ will give you some statements of the num- 
bers of animals from Agassiz and Gould. The number 
