CH. IXJ THE PRODUCTIVITY OF THE SEA 203 



Macrocystis pyrifera. This plant gi'ows on every rock from low 

 watermark to a great depth, both on the outer coast and within 

 the channels. I believe during the voyages of the Adventure and 

 Beagle not one rock near the surface was discovered which was not 

 buoyed by this floating weed." It grows up from the depth of 

 45 fathoms. " The number of living things of all Orders, whose 

 existence intimately depends on the kelp, is wonderful. A great 

 volume might be written describing the inhabitants of one of these 

 beds of sea-weed. Almost all the leaves, excepting those that float 

 on the surface, are so thickly encrusted with corallines as to be of 

 a white colour. We find exquisitely delicate structures, some 

 inhabited by simple hydra-like polypi, others by more organised 

 kinds, and beautiful compound ascidiae. On the leaves also, various 

 patelliform shells, Trochi, uncovered molluscs, and some bivalves, 

 are attached. Innumerable Crustacea frequent every part of the 

 plant. On shaking the great entangled roots, a pile of small fish, 

 shells, cuttlefish, crabs of all orders, sea-eggs, starfish, beautiful 

 Holothuria, Planaria, and crawling nereidous animals of a multi- 

 tude of forms, all fall out together.... I can only compare these 

 great aquatic forests of the southern hemisphere with the terrestrial 

 ones in the intertropical regions. Yet if in any country a forest 

 were destroyed, I do not believe nearly so many species of animals 

 would perish as would here from the destruction of the kelp. 

 Amidst the leaves of this plant numerous species of fish live, which 

 nowhere else could find food or shelter ; with their destruction the 

 many cormorants and other fishing birds, the otters, seals and 

 porpoises, would soon perish also ; and lastly, the Fuegian savage, 

 the miserable lord of this miserable land, would redouble his 

 cannibal feast, decrease in numbers, and perhaps cease to exist." 

 Just as the algal flora and the benthic and nektic life of 

 the temperate and polar seas are richer than those of the tropical 

 waters, so too the plankton of the colder waters is more abundant, 

 though perhaps less varied, than that of the warmer. The whale- 

 bone whales are plankton feeders, and one may well wonder at 

 the huge masses of pteropods that must exist in Arctic seas to 

 afford the necessary amount of food for these enormous creatures. 

 Then the richness of the diatom flora of the polar seas is well 

 known. At times the water is visibly discoloured by these 

 organisms, and we are told that fishing operations in northern 



