ii DECOMPOSITION OF CARBON DIOXIDE 29 



Hrematococcus lives in rain-water. This is never pure 

 water, but always contains certain mineral salts in solution, 

 especially nitrates, ammonia salts, and often sodium chloride 

 or common table salt. These salts, being crystalloids, can 

 and do diffuse into the water of organization of the ani- 

 malcule, so that we may consider its protoplasm to be con- 

 stantly permeated by a very weak saline solution, the most 

 important elements contained in which are oxygen, hydro- 

 gen, nitrogen, potassium, sodium, calcium, sulphur, and 

 phosphorus. It must be remarked, however, that the 

 diffusion of these salts does not take place in the same uni- 

 form manner as it would through parchment or other dead 

 membrane. The living protoplasm has the power of 

 determining the extent to which each constituent of the 

 solution shall be absorbed. 



If water containing a large quantity of Hsematococcus 

 is exposed to sunlight, minute bubbles are found to appear 

 in it, and these bubbles, if collected and properly tested, 

 are found to consist largely of oxygen. Accurate chemical 

 analysis has shown that this oxygen is produced by the de- 

 composition of the carbon dioxide contained in solution in 

 rain-water, and indeed in all water exposed to the air, the 

 gas, which is always present in small quantities in the 

 atmosphere, being very soluble in water. 



As the carbon dioxide is decomposed in this way, its 

 oxygen being given off, it is evident that its carbon must be 

 retained. As a matter of fact it is retained by the organism 

 but not in the form of carbon ; in all probability a double 

 decomposition takes place between the carbon dioxide ab- 

 sorbed and the water of organization, the result being the 

 liberation of oxygen in the form of gas and the simultaneous 

 production of some extremely simple form of carbohydrate, 

 i.e. some compound of carbon, hydrogen, and oxygen, 



