3. 



and NH4OH. The acids wore HC1, CK3COOH and C02 and the salts Na2C03, NaHCOg, 

 Ka2HP04 and NaH2P04. Those workers found th^t bases, exoept NH4OH, give 

 acceleration of development in low concentrations, while higher concentrations 

 cheek development and finally kill. Acids all inhibit. The primary factors 

 affeoting the rate of growth appear to be the variations in concentration of 

 hydrogen and hydroxyl ions. Thus all of the caustic alkalies are of approx- 

 imately equal power and there is little or no action of the cations. But in 

 the case of the phosphates, where the hydrogen-hydroxyl ion concentrations are 

 comparatively low, there seems in addition to be a specific factor. The 

 extreme limits of variation of hydrogen and hydroxyl ion concentrations within 

 which growth is possible are shown to be very narrow, .0015 M. caustic alkali 

 or .001 M acid practically stopping all development. Whitley (1905) showed 

 the same relationship between hydrogen-hydroxyl ion concentration and development 

 to hold for the eggs of Pleuronctes platsssa. He gives three reasons why 

 alkali is less harmful than acid: 



1* Alkali added to sea water is immediately thrown out as insoluble 

 hydrates or oarbonates. 



2. Alkali is constantly used up to neutralize CO2 produced by the 



animal. 



3. Loeb has shown a low quantity of alkali increases the permea- 

 bility to 03. This may increase the resisterce of the egg. 



Finally Grace Medes (1918) has shown that changes in the composition of the sea 



water by concentration, dilution or addition of acids, bases or salts in non 



concentrations 

 lethal cause a retardation of development of the eggs of arbacia punctuUta. 



Excepting for the experiments of Loeb in 1898 on Fundulus eggs, 



nearly all of the work so far done on the effects of bases and acids on 



development has been done upon marine animals. Many of the most serious 



