. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. 1 PELAGIC ANIMAL LIFE 579 No class of multicellular animals in the ocean is represented by any- Crusts thing like such countless forms and individuals as that of the Crustaceans • in the life of the ocean they play, according to Haeckel, a part corre- sponding to that of the insects in the land fauna. The Entomostraca include the most important groups, first the Copepoda, then the Ostracoda, and
. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. 1 PELAGIC ANIMAL LIFE 579 No class of multicellular animals in the ocean is represented by any- Crusts thing like such countless forms and individuals as that of the Crustaceans • in the life of the ocean they play, according to Haeckel, a part corre- sponding to that of the insects in the land fauna. The Entomostraca include the most important groups, first the Copepoda, then the Ostracoda, and the Cladocera. Among the larger Crustacea, the Schizopoda the Amphipoda, and the Decapoda are also very important but m abundance and specific variation they can never be compared to the groups of smaller crustaceans. The Copepoda as a rule, attain only a few millimetres in length, and Copepodn aie adapted to feed on the small plants of the oceanic flora in the upper ? " layers of all oceans. It may safely be asserted that they are the chief consumers of these minute plants, and in turn serve as food for arger animals. Giesbrecht1 discusses the geo- graphical distribution of 299 species of Copepoda, and divides the area of their distribution into three regions: (1) a warm region between 47°^ N. and 440 S., (2) a northern region, and (3) a southern region. The warm region comprises all the oceans, the warm - water species throughout the world being more alike than the species of warm and cold regions in the same ocean. Of the 299 species, no less than 254 belong exclusively to the warm region ; there are besides a few widespread forms and others peculiar to the northern or southern region. About 85 per cent of the species belong to the warm region, 5 per cent to the northern and 2 per cent to the southern region. As characteristic of the warm region Giesbrecht mentions the follow- ing genera : Augaptilus, Calocalanus, Copilia, Euchirella, Hemicalanus Monops, Pleuromma, P
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