54 Prof. B. Moore, Messrs. E. Whitley, and T. A. Webster. 



rapid increase in hydroxyl-iou concentration and fall in liydrogen-ion 

 concentration. 



It is this accumulation of alkali which limits photo-synthesis by killing the 

 cell, for up to quite close to this " all-carbonate " point the cell flourishes and 

 synthesises rapidly, but if kept for some time by too violent exposure to 

 sunlight at this point, the algae turn yellow and the growth is killed, for 

 there is no recovery, even if removed from the strong light. The degree of 

 alkalinity reached by the green cell before death is, however, remarkable. 

 It is much greater than anything which can be borne by any mammalian 

 cell, and even by any delicate marine animal organism, such as a developing 

 embryo plaice or a fertilised echinus egg. 



The increase of hydroxyl-ion concentration and corresponding decrease in 

 hydrogen -ion concentration are such ' that the water shows a full pink with 

 phenolphthalein, and is more alkaline than the full strength of the deci- 

 normal " alkaline phosphate " (Na2HP04) in the Sorensen phosphatic mixtures 

 for determination of hydrogen-ion concentration. This means, expressed in 

 the usual logarithmic notation, a concentration of less than Ph, 10~^'^. 



This increase of alkalinity is about equal to that shown in 1905 by Moore, 

 Eoaf, and Whitley* to promote disordered cell-division, and, later, death in 

 the dividing cells of fertilised echinus eggs. Now, when the sunshine is 

 strong in Spring and Summer, in every pool upon the seashore above half- 

 tide level, when isolated from the sea, such active photo-synthesis must 

 proceed with development of alkalinity, and such changes must have a marked 

 effect upon any animal forms of life in the pool. Such environmental 

 changes, with their stimulating action upon cell-division may play a part in 

 originating deviations and producing variations. In "Winter such influences 

 would be slight, but as the Spring days lengthen and the altitude of the sun 

 increases their power augments and reaches a maximum just as reproductive 

 processes and rapid cell-division are at their height. In the experiments 

 recorded below, in order to prevent death from alkalinity, a supply of 

 carbon dioxide was given by blowing air from the lungs through the sea- 

 water in which those algse were immersed, which were exposed to full day 

 or sunlight whenever the titrations showed an approach to the lethal limit. 



The main series of experiments was carried out during the period of 

 March 28th till April 5th, 1919, in two sets of twelve each of the Kilner 

 fruit-preserving jars, each of about 800 c.c. capacity and provided with air- 

 tight screw-down lids, as described in a previous pa per f Afterwards, for 

 purposes of analysis, the two sets at the end were combined and preserved 



* Moore, Eoaf, and Whitley, ' E07. See. Proc.,' B, vol. 77, p. 102 (1905). 

 t Moore and Webster, loc. cit. 



