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SCIENCE 



[N. S. Vol. XXIX. No. 742 



tative Marine Biology and Metabolism of the 

 Sea. Part II. is, on the whole, the most satis- 

 factory portion of the book. The author is at 

 his best when dealing with actual observations 

 and matters of fact in such a way that his 

 general biological theories have no visible in- 

 fluence on his conclusions, and it is unfor- 

 tunate that the whole book could not have 

 been written with a mind thus unhampered. 



Although Mr. Johnstone's adherence to the 

 Hensen ideas is unqualified it is not slavish. 

 Most, though by no means all, of the more 

 telling criticisms passed upon the methods and 

 results of the Kiel school are duly heeded. 

 The methods of collecting developed up to 

 date are treated to the extent of nearly ten 

 pages, and Lohmann's interesting observa- 

 tions on the capture of plankton by appendi- 

 cularia is adequately noticed. The four 

 methods of estimating the quantity of 

 plankton, viz., the volumetric, chemical, gravi- 

 metric and numerical, are considered both as 

 to processes and reliability. Of these " the 

 actual counting of the organisms is the most 

 satisfactory." 



The surface distribution of certain kinds of 

 planktonic organisms in the north Atlantic 

 is illustrated chiefly by reference to Clove's 

 work. Two instructive charts accompany this 

 discussion. 



A chapter devoted to A Census of the Sea, 

 and another on The Productivity of the Sea, 

 summarizes considerable of the data on these 

 subjects, though by no means all that has 

 been gathered by the investigators of the 

 north Atlantic. 



On the question of the depletion of the sea 

 through fishing, the author, though admitting 

 the absence of conclusive proof on either side, 

 and noting the authoritative opinion against 

 exhaustion, thinks " we can not come to any 

 other conclusion than that fishing operations 

 as at present carried on, do cause a very ap- 

 preciable diminution of the stock of fish on 

 the sea bottom." More reliance is placed on 

 Hensen's investigations than on any others 

 for this conclusion. 



Greater productivity of the ocean in high 

 latitudes than in low is regarded by the au- 

 thor as proved. The three chief explanations 



of this supposed fact are considered in part 

 III. Brandt's conjecture that denitrifying 

 bacteria are more active in warmer waters 

 and hence prevent these from containing as 

 ample a supply of nitrogenous food-salts for 

 the phyto-plankton as the colder waters have, 

 is held to be " not the only hypothesis capable 

 of explaining" the phenomenon. ISTathanson 

 has suggested that in some localities at least, 

 colder waters may contain greater quantities 

 of organic matter because they have up-welled 

 from the bottom or deeper water where such 

 matter has gradually accumulated through 

 the settling into them of the carcases of or- 

 ganisms that have lived in the lighter waters 

 above; or through the transferrence to them 

 by convection-currents of warmer surface 

 water from middle latitudes that have been 

 enriched in organic matter by rivers from 

 land areas clothed with vegetation of tropical 

 luxuriance. Johnstone thinks this hypothesis 

 worthy of consideration. 



Finally the explanation proposed by Piitter 

 is presented. This author supposed, to state 

 the case in a nutshell, that animals inhabit- 

 ing warm waters live faster than those in- 

 habiting cold waters and so consume more 

 food. Consequently since the food supply is 

 everywhere limited, a less numerous popula- 

 tion can be maintained in the warmer than 

 in the colder seas. 



Among the many interesting subjects 

 treated in part HI., none is more interesting 

 than that of nitrogen in the sea and the re- 

 lation of bacteria to this element. 



That imagination would be dull indeed that 

 should not be kindled by the picture outlined 

 in this part of the book of what the earth 

 really is as a habitation for living beings. 

 The truly cosmic character of the problems 

 the threshold of which has been crossed by 

 Brandt and the few other foremost investiga- 

 tors in this realm, is well brought home to the 

 reader. 



The book ends with several useful append- 

 ices, one of which is a summary of A. B. 

 Macallum's interesting though not convincing 

 speculations on the chemistry of the early 

 seas, and the impress this has left on living 

 beings down to even the present. 



