Royal Institution. 233 



this zone, wherever the ground is hard or rocky, thus affording secu- 

 rity for the gi'owth of marine plants and animals, presents similar 

 features and can be subdivided into a series of corresponding sub- 

 regions ; through all of which the common limpet {Patella v\d(jatd) 

 ranges, giving a character to the entire belt. Each of these sub- 

 regions has its own characteristic animals and plants. Thus, the 

 highest is constantly characterized by the presence of the periwinkle 

 Littorina rudis (and on our western shores, Littorina neritoides) along 

 with the sea-weed Fucus canaliculatus. The second subregion is 

 marked by the sea-weed Lichina and the common mussel {Mytilus 

 edulis). In common with the third subregion it almost always pre- 

 sents rocks thickly encrusted with barnacles, so that where our shores 

 are steep, a broad white band entirely composed of these shell-fish 

 may be seen when the tide is out, marking the middle space so con- 

 spicuously as to be visible from a great distance. In the third sub- 

 region the commonest form of wrack or kelp {Fucus articulatus) 

 prevails, and the large periwinkle {Littorina littorea) with Purpura 

 Capillus are dominant and abundant. In the fourth and lowest sub- 

 region the Fucus just mentioned gives way for another species, the 

 Fucus serratus ; and in like manner the shells are replaced by a fresh 

 Littorina {littoralis) and peculiar Trochi. 



Once below low-water mark the periwinkles become rare, or dis- 

 appear, and the Fuci are replaced by the gigantic sea-weeds known 

 popularly as tangles (species oi Laminaria, Alaria, &c.), among which 

 live myriads of peculiar forms of animals and lesser plants. The ge- 

 nus Lacuna among shell-fish is especially characteristic of this zone. 

 In sandy places the Zostera or grass-wrack replaces the Laminaria. 

 TheLAMiNARiAN ZoNE cxtends to a depth of about fifteen fathoms, 

 but in its lowest part the greater sea-weeds are comparatively few, and 

 more usually the prevailing plant is the curious coral-like vegetable 

 called NulUpore. 



From 15 to 50 or more fathoms we find a zone prolific m pecuUar 

 forms of animal life, but from which conspicuous vegetables seem 

 almost entirely banished. The majority of its inhabitants are pre- 

 dacious. Many of our larger fishes belong to this region, to which, 

 on account of the plant-like zoophytes abounding in it, the name of 

 Coralline Zone has been applied. The majority of the rarer shell- 

 fish of our seas have been procured from this region. 



Below 50 fathoms is the Region of Deep-Sea Corals, so styled 

 because hard and strong true corals of considerable dimensions are 

 found in its depths. In the British seas it is to be looked for around 

 the Zetlands and Hebrides, where many of our most curious animals, 

 forms of zoophytes and Echinoderms, have been drawn up from the 

 abysses of the ocean. Its deepest recesses have not as yet been ex- 

 amined. Into this region we find that not a few species extend their 

 range from the higher zones. When they do so they often change 

 their aspect, especially so far as colour is corcerned, losing brightnesa 

 of hue and becoming dull-coloured or even colourless. In the lower 

 zones it is the association of species rather than the presence of pecu- 

 liar forms which gives them a distinctive character. All recent re_ 



