The universal features of zonation between tide-marks on rocky coasts

So much has already been discovered about life between tide-marks that it has become difficult to see the wood for the trees. Yet despite the host of publications dealing with intertidal life, the field untouched is so vast that our knowledge of the natural laws which control intertidal affairs is still elementary. For these reasons we must examine intertidal arrangements, where possible, on a broad scale as well as intensively. Until recently there has been a stronger tendency to study the problems of tidal biology in great detail on a small scale than in less detail on a large one. This has resulted in many accounts of the natural history of individual plant and animal species, and in numerous descriptions of the occurrence of plants, animals (or both) in small areas varying in size from square yards, individual rock-pools or narrow traverses to short stretches of coastline, estuaries and similar areas. The general examination of long stretches of coast, or of the coastlines of whole countries, has lagged far behind the more detailed studies, and there have been few examples of it. We have, it is true, such surveys as those of Fischer-Piette on the European coasts, of Ricketts on the Pacific coast of North America, and of the present authors and their collaborators in South Africa; but the list is not a long one. Recent progress in intertidal studies has been ably summarized by Fischer-Piette (1940), and the volume in which his paper appears represents, as a whole, an important contribution to the subject. At the present time there is evidence of a tendency to undertake the examination of long coastlines more readily than before, and this is of course facilitated by car and plane travel, and by the construction of roads in many places which were previously inaccessible. An example of such work is the survey, by Dakin and his assistants, of 1000 miles of coastline in New South Wales, the results of which were published in 1948. A series by R. G. Evans on parts of the British coast is at present appearing, and while this deals with much shorter stretches, its point of view is a broad one, looking towards an eventual general account of the British coasts. There is similar work now progressing in several parts of the