must have been sufficient nitrogenous and other food material to make them thrive so well—possibly the excreta or rotting carcase of a whale!
Now in the Antarctic seas, especially during my cruise in 1892 and 1893, I have recorded in my diary day after day such entries as these: "sea dirty green"; "sea dirty brown"; "sea dirty olive-brown"; "brownish green sea"; "olive-brown sea"; "sea green"; "water olive-green colour," and so on. When the silk tow-net was put over, it was quickly filled with a gelatinous mass, which adhered persistently to the silk, and which, even after thorough washing, blocked up the fine meshes, which could not be washed clear of it. On examination I found this slimy mass to be composed of Corethron cryophyllum and other diatoms.
Like the yellow bands of algæ in the South Atlantic Ocean, the immense quantity of diatoms and other algæ floating in the polar seas doubtlessly forms the basis of the enormous abundance of animal life there, from the small copepods and euphausia to the innumerable birds, seals, and giant whales. The nature of this discoloration of Arctic waters was shown by the late Dr. Robert Brown (Transactions, Botanical Society, Edinburgh, vol. ix, 1867) to be due to the presence of enormous numbers of diatoms, among
