LIFE IN THE OCEAN * 



By Austin H. Clabk 



PREFACE 



A comparison of the animals living in the sea with those inhabit- 

 ing the land brings out at once a most extraordinary paradox. 



About three-fourths of all known kinds of animals live on the 

 land; but this formidable array represents only a few of the major 

 types. The most numerous land creatures are the insects, of about 

 half a million sorts. Equal in importance, much larger, but much 

 fewer both in kinds and numbers, are the vertebrates. Next in sig- 

 nificance are the nematodes. Of much less importance are the mol- 

 lusks — snails and slugs — and the annelids — earthworms, land leeches, 

 and onychophores. The representatives of the other major types 

 found on the land, planarians and nemerteans, are not of much im- 

 portance in the picture as a whole. 



While in the sea there live less than one-fourth of all the animals 

 that so far have been described, these are widely distributed among 

 about three times as many major types as are those inhabiting the 

 land. 



Certain marine types, like sponges, ccelenterates , and polyzoans, 

 and some groups of annelids, are sparsely represented in fresh water, 

 which also has some types, like gastrotrichas and the rotifers, quite 

 or almost wholly restricted to it. But of the major animal types no 

 less than 10 (priapulids, sipunculids, phoronids, brachiopods, chse- 

 tognaths, echinoderms, enteropneusts, tunicates, and cephalochor- 

 dates), nearly half again as many as all land-living types together, 

 are exclusively marine. 



Qn land different localities and situations are extremely variable 

 as regards the physical conditions. We find hot, temperate, and 

 cold, and uniform and changing, regions; dry, damp, and wet areas, 

 permanent or changeable. All these features, together with the 

 chemical variability of the soil, are reflected in the flora of the land, 

 and all these features plus the superadded features of the flora, affect 



1 Reprinted, slightly abridged, by permission of the publishers, from Animal Life of Sea 

 and Land, D. Van Nostrand Co., New York, 1924. 



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