Microscope at Sea 31 



floating plants, large and visible like the sea-weeds of 

 the coast, form the floating masses known as Sargasso 

 seas ; more often the plants are minute, microscopic 

 specks visible only when a drop of water is placed under 

 the microscope, but occurring in incredible numbers, 

 and, like the green vegetation of the earth, forming the 

 ultimate food-supply of all the living things around 

 them. Innumerable animals, great and small, live on 

 the plants or upon their fellows, and, however far he 

 may be from land, the naturalist has always abundant 

 material got by his daily use of the tow-net. This 

 drifting population floats at the mercy of the waves. 

 Most of the animals are delicate, transparent creatures, 

 their transparency helping to protect them from the 

 attacks of hungry fellows. Nerves, muscles, skin, 

 and the organs generally are clear, pale, and hardly 

 visible. Such structures as the liver, the reproductive 

 organs, and the stomach, which cannot easily become 

 transparent, are grouped together into small knots, 

 coloured brown like little masses of sea-weed. Other 

 floating creatures are vividly coloured, but the hues are 

 bright blues and greens closely similar to the sparkling 

 tints of sea- water in sunlight. The different members 

 of this marine flotsam frequently rise and fall periodi- 

 cally: some of them sinking by day to escape the light, 

 others rising only by day ; others, again, appearing on 

 the surface in spring, keeping deep down in winter. 

 Perhaps the majority of them are phosphorescent, some- 

 times shining b}' their own light, sometimes borrowing 

 a glory from innumerable phosphorescent bacteria with 

 which they are infested. Nearly every class of the 

 animal kingdom contributes members to this strange 

 population. The j^oung forms of man}- fish, as for in- 

 stance of conger, flying gurnards, and some flatfish, are 



