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XV. Remarks upon the Theory of' Reciprocal Dependence in 

 the Animal and Vegetable Creations, as regards its bearing 

 upon Pala 'ontology. By Herbert Spencer'*, 



TPOM perusing an article which some time since appeared 

 *-^ in the Philosophical Magazine explanatory of M. Dumas' 

 views respecting the peculiar relationship that exists between 

 plants and animals f, in so far as their action upon the atmo- 

 sphere is concerned, it occurred to me that the doctrine there 

 set forth involved an entirely new and very beautiful explanation 

 of the proximate causes of progressive development; and as the 

 idea does not seem to have been yet started, perhaps I may be 

 allowed to make your Journal the medium for its publication. 



In unfolding the several results of the theory and exhibiting 

 its application in the solution of natural phaenomena, M. 

 Dumas adverts to the fact, that not only do the organisms of 

 the vegetable kingdom decompose the carbonic acid which 

 has been thrown into the atmosphere by animals, but that 

 they likewise serve for the removal of those extraneous sup- 

 plies of the same gas that are being continually poured into it 

 through volcanos, calcareous springs, fissures, and other such 

 channels. It is to the corollary deducible from this proposi- 

 tion, respecting the alterations that have taken place in the 

 composition of that atmosphere, that attention is requested. 



If it had been found that during the past epochs of the 

 world's existence animals had always borne such a proportion 

 to plants as to ensure the combustion of the whole of the 

 carbon assimilated by them from the air, or in other words, 

 if the carbon -reducing class had always been exactly balanced 

 by the carbon-consuming class, it would then follow, that as 

 the gas decomposed in the one case was wholly recomposed in 

 the other, the only change that could have taken place in the 

 character of the atmosphere would have been a deterioration 

 resulting from the continual influx of carbonic acid from the 

 above-mentioned sources. Such, however, were not the con- 

 ditions of the case, for it is manifest, not only from the nature 

 of existing arrangements, but likewise from the records of the 

 world's history, that the vegetable kingdom has always had 

 such a preponderance as to accumulate a much larger supply 

 of carbon than could be consumed by animals. This was 

 especially the fact in the earlier seras. During those vast periods 

 that expired before the appearance of mammalia, and whilst 

 animate life was chiefly confined to rivers and seas, nearly the 

 whole of the immense masses of vegetation that then covered 

 the land, apparently with a much more luxuriant growth than 



* Communicated by the Author. f Phil. Mag. S. 3. vol. xix. p. 337- 



