LITTORAL. 797 
oxygen ; it is quite calm, for even the greatest storms are 
relatively shallow in their influence; there are no plants 
(except perhaps the resting phases of some Algz), for 
typical vegetable life depends upon light, and not even 
bacteria, otherwise almost omnipresent, are known to 
flourish in the great depths. A strange, silent, cold, dark, 
-plantless world! The animals feed upon one another and 
upon the débris which sinks from above. 
We do not clearly know when the colonising of the depths began, 
but there is much to be said for the view that an abyssal fauna was, at 
most, scanty before Cretaceous ages. But whensoever the peopling of 
the abysses occurred, it must have been gradual. It is likely that most 
of the pioneers migrated outwards and downwards from the shore 
region (in a wide sense), following the drift of food ; it is possible that 
others, e.g. some Crustaceans, sank from the surface of the open sea. 
The boreal character of many deep-sea animals has been often remarked, 
and it is plausible to suppose that there was a particularly abundant 
colonisation in the Polar regions, and a gradual’ spreading towards the 
Equator as the Poles became colder. - Perhaps the richness of the fauna 
at the Equator may be thought of as in part due to the meeting of two. 
great waves of life from the Poles. 
The abyssal conditions of life tend to uniformity over vast 
areas, just as in the open sea. But, on the whole, life must 
always have been harder in the depths that on the surface. 
The absence -of plants, for instance, involves a keener 
struggle for existence among animals. Thus, although 
many abyssal forms, ¢.g. sea-anemones, live a passive séden- 
tary life, waiting for food to drop into their mouths, the: 
majority are less easy-going. The deep sea has been a 
sterner school of life than the surface. 
Littoral.—At a very early date the shores were peopled, 
and the fauna is very rich and representative. From the 
strictly Littoral zone, exposed at low tide, with its acorn- 
shells and periwinkles, limpets and cockles, to the Lam- 
inarian zone (to 15 fathoms), with its sea-slugs and oysters, 
where the great seaweeds wave listlessly amid an extremely 
keen battle, to the Coralline zone (15-40 fathoms), with its. 
carnivorous buckies, what variety and abundance, what 
crowding and struggle ! ; 
There are Infusorians and Foraminifera, horny, flinty, and’ 
calcareous Sponges, zoophytes and sea-anemones, many 
“worms,” star-fishes and sea-urchins, crabs and shrimps, 
