360 COMPARATIVE ZOOLOGY. 
of the food. Carnivores have a wider range than herbi- 
vores. 
Life diminishes as we depart from the equator north or 
south, and likewise as we descend or ascend from the level 
of the sea. 
The zones of geography have been divided by zoologists 
into narrower provinces. Five vertical regions in the sea 
have been recognized: the Littoral, extending between 
tide-marks; the Laminarian, from low water to 15 fath- 
oms; the Coralline, from 15 to 20 fathoms; the deep-sea 
Coral, from 50 to 100 fathoms; and the Bathybian, from 
100 fathoms down. Every marine species has its own 
limits of depth. It would be quite as difficult, said Agas- 
siz, for a Fish or a Mollusk to cross from the coast of 
Europe to the coast of America as for a Reindeer to pass 
from the arctic to the antarctic regions across the torrid 
zone. Marine animals congregate mainly along the coasts 
of continents and on soundings. The meeting-place of 
two maritime currents of different temperatures, as on 
the Banks of Newfoundland, favors the development of 
a great diversity of Fishes. | 
Every great province of the ocean contains some repre- 
sentatives of all the subkingdoms. Deep-sea life is diver- 
sified, though comparatively sparse. Examples of all the 
five invertebrate divisions were found in the Bay of Bis- 
cay, at the depth of 2435 fathoms.** 
Distribution in the sea is influenced by the temperature 
and composition of the water, and the character of the 
bottom. The depth acts indirectly by modifying the tem- 
perature. Northern animals approach nearer to the equa- 
tor in the sea than on the land, on account of cold cur- 
rents. The heavy aquatic Mammals, as Whales, Walruses, 
Seals, and Porpoises, are mainly polar. 
The land consists of the following somewhat distinct 
areas: the Neotropic, comprising South America, Mexi- 
