64 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



" (II.) The second series of researches dealt with the import- 

 ant observation that the hydrogen-ion concentration of sea- 

 water determining its degree of akalinity or acidity does not 

 remain constant throughout the year, but varies with the 

 relative activities of vegetable and animal organisms and acts 

 as an index to these activities. 



" There are two maxima of alkalinity, or minima of 

 hydrogen-ion concentrations, corresponding (with a slight lag 

 in time) to the two seasonal outbursts of diatoms. 



" The change observed indicates a synthesis at these 

 seasons of some tons (per acre of sea- water) of organic vegetable 

 matter for the nutrition of the animals. 



" The green plant or diatom breaks up the bi-carbonates 

 present in sea-water, and synthetically forms organic com- 

 pounds. The amount of the removal of carbon-dioxide is 

 shown by the increase in alkalinity. A portion of green plant 

 placed in sea-water and exposed to sunlight causes this decom- 

 position with remarkable rapidity. The rise in alkalinity is a 

 surprising one, and it has been shown that it has a very definite 

 end-point, namely that the plant continues its activity up to 

 the limit at which all bi-carbonates have been converted into 

 normal carbonates and then ceases. At this level the alkalinity 

 is equivalent to that of a deci-normal solution of alkaline 

 sodium phosphate (Na 2 HP0 4 ), and is outside the limits on the 

 Sorensen scale of even phenol-phthalein as an indicator. 



" In the open sea the amount of vegetation is not, of 

 course, sufficient to drive the reaction to this limit ; if it were, 

 the alkalinity would probably be sufficient to kill all the animal 

 plankton in the water. It is noteworthy that the spring 

 increase in alkalinity is just of the grade formerly shown by 

 Moore, Koaf and Whitley to be most favourable to rapidity of 

 subdivision in the initial stages of development of the eggs of 

 Echinus. 



