22 LIFE BY THE SEASHORE. 



when they are deeply fissured and hollowed out, leaving 

 many shady corners and deep pools ; for in the former the 

 sedentary forms will be found, while the latter act as traps 

 to the floating population. It is not, however, sufficient that 

 pools and fissures should exist : there must also be ready 

 access to them. In the case of stratified rocks readiness of 

 access depends largely upon what geologists call the dip. 

 The ideal case is, perhaps, that where the rocks run out to 

 sea in long ridges of which each stratum overhangs its 

 neighbour, while between successive ridges are long channels 

 whose contents are available until the tide actually covers 

 the ridge. When, on the other hand, the rocks dip outwards 

 to the sea, these same channels form dangerous pitfalls to 

 the too enthusiastic naturalist, who lingers on the distant 

 ridges regardless of the eddying currents which are cutting 

 off his retreat. This danger is sufficiently real to make it 

 decidedly worth while to take a general survey of the rocks, 

 and study their peculiarities before beginning serious work. 



This done, there still remains one more point to settle, 

 and that is the part of the rocks to which our energies are 

 to be devoted. Broadly speaking, there are two possibilities 

 the strictly littoral rocks, those which are exposed at 

 ordinary low tide, and are only completely covered for a 

 relatively brief period about the time of high tide ; and the 

 Laminarian zone, which is only accessible for a short time at 

 extreme low water during spring tides, and then only in 

 part. It is in the pools sheltered beneath the long fronds of 

 Laminaria, or oar-weed, that the greatest treasures are to 

 be found the tiny Eolis coronata, with its brilliant colour- 

 ing in blue and crimson; the active Galatheas, darting back- 

 wards through the pools; the larger Annelids, with their 

 bright pigments and gleaming iridescence, and many others 

 but the time during which these pools are accessible is 

 woefully brief, and the beginner is recommended to confine 

 himself, at least at first, to the rocks nearer the shore. 



Let us suppose ourselves, then, ready to start for an 

 introductory expedition to the rocks. First, as to the 

 equipment, let this be as simple as possible ; the danger lies 

 not in collecting too little, but in the general case in 

 attempting too much. According to my experience the 

 average beginner provides himself with numerous buckets 



