CH. Ill] LIFE IX THE SEA 57 



is due also the term benthos, coined the word " Nekton," and the 

 term has come into general use. There is, of course, no absolute 

 distinction between these three classes of organisms. That is, 

 there are creatures which, like the molluscs and Crustacea, belong 

 in their adult phases to the benthos, but which in the larval state 

 live among the plankton ; while on the other hand there are some 

 animals, such as the fishes, which are inhabitants of the nekton 

 but which are also in the young state to be reckoned among the 

 plankton. Then one at times finds it diflicult to say whether 

 organisms, like the medusae, which are carried about in great 

 swarms by tides and currents, but which nevertheless are capable 

 of some degree of locomotion, are to be included in the plankton 

 or in the nekton. But this lack of absolute distinction, which 

 is to be felt in all schemes of classification of natural objects, 

 is no argument against the use of a series of terms which are 

 sufficiently exact, are expressive, and have great practical con- 

 venience. 



Just because of this practical convenience we also still employ 

 Forbes' regions or zones, or some modification of these. They 

 apply only to the benthos or bottom-living population, but every- 

 one who has dredged or trawled recognises the variation in the 

 characteristic fauna and flora as we descend the sea slope from the 

 upper tide mark. Forbes' littoral zone is the foreshore, that 

 margin of sea-coast between high and low tide marks, the right 

 to which has so often been the subject of vexatious litigation, 

 On the foreshore we find a population, the nature of which varies 

 with that of the sea bottom. The littoral zone of Forbes was 

 a gravelly or rocky seashore and contained abundance of sea- weeds 

 such as the bladderwrack (Fucus), the fine green weed (Entero- 

 morpJia), or the sea-grass {Zostera). On it, in our country, are 

 abundance of shellfish like the mussels, dogwhelks {Purpura), 

 limpets and periwinkles. The acorn barnacle (Balanus) may cover 

 the stones. In the rock pools are crabs, small fishes, worms, 

 zoophytes and many other creatures. Such is the littoral 

 zone of the collector. But we may find that it is a shifting 

 expanse of sand or of sand and mud, and here there are none of the 

 organisms mentioned, or they occur very sparingly and an entirely 

 different fauna and flora are to be found. In their place may be 



