392 THE WORLD OF LIFE 



are secreted. It was on these special features of carbon that 

 Haeckel founded his celebrated carbon-theory of life, which 

 he has thus stated : '^ The peculiar chemico-physical properties 

 of carbon — especially the fluidity and the facility of decom- 

 position of the most elaborate albuminoid compounds of car- 

 bon — are the sole and the mechanical causes of the specific 

 phenomena of movement, which distinguish organic from in- 

 organic substances, and which are called life, in the usual sense 

 of the word.'' And he adds : " Although this ' carbon-theory ' 

 is warmly disputed in some quarters, no better monistic theory 

 has yet appeared to replace it." 



What a wonderfully easy way of explaining a mystery! 

 Carbon forms a constituent of the bodies and of the products 

 of all living things ; therefore carbon is the cause of life and all 

 its phenomena ! 



But besides the carbon in the atmosphere an immense quan- 

 tity exists in the various limestone rocks, consisting of car- 

 bonate of lime (CaCOg). It is quite possible, however, that 

 these are all results of animal secretions as in coral-reefs; or 

 of the debris of the hard parts of marine animals, as in the 

 Globigerina-ooze. Limestones exist among the oldest rocks, 

 but as we know that marine life was very much older, this is 

 no objection. All water holds in solution a large quantity of 

 carbonic acid gas, so that both air and water are the source 

 of the most essential elements for building up the bodies of 

 plants and animals. 



The ocean also holds a large amount of carbonate of lime 

 in solution, and this is kept permanently dissolved by the large 

 amount of carbonic acid gas always present, which is sufficient 

 to dissolve five times the amount of carbonate of lime which 

 actually exists. Deposits of inorganic limestone are, there- 

 fore, now never formed except by long-continued evaporation 

 in isolated bodies of salt water. This renders it more probable 

 that all pure limestone rocks are really very ancient coral-reefs 

 consolidated and crystallised by heat and pressure under masses 

 of superincumbent strata. 



