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 Algae), for 

 typical vegetable life depends upon light, and not even 

 bacteria, otherwise almost omnipresent, are known to 

 flourish in the great depths. A strange, ^ilent, cold, dark, 

 plantless world ! The animals feed upon one another and 

 upon the debris 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, e.g. sea-anemones, live a passive seden- 

 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, 



