Vol. XLV1I December, i Q2 4 No. 6 



BIOLOGICAL BULLETIN 



THE INFLUENCE OF HYDROGEN ION CONCENTRA- 

 TION ON THE DEVELOPMENT OF NORMALLY FER- 

 TILIZED ARBACIA AND ASTERIAS EGGS. 



HOMER W. SMITH AND G. H. A. CLOWES. 



(From the Lilly Research Laboratory, Indianapolis and the Marine Biological 



Laboratory, \Yoods Hole). 



The belief that cessation and initiation of development in the 

 marine egg depended in some manner on the ionic equilibria of 

 sea water led Loeb (i) to examine the influence of changes in the 

 concentration of H- and OH-ions on the development of normally 

 fertilized eggs. He found that the development of the eggs of 

 Arbacia is retarded and finally prevented if increasing quantities 

 of acid are added to sea water, and that the development to the 

 pluteus stage is accelerated in alkaline sea water. The latter fact 

 was indicated by the advanced size and development of the plutei 

 formed from the treated eggs as compared with controls. On 

 subsequent investigation he concluded that alkali does not ac- 

 celerate the early cleavage rate, but only the later development 

 from the blastula to the pluteus. The addition of excessive 

 quantities of alkali had an injurious effect. The maximum stimu- 

 lation was observed when 1.7500. N/io NaOH were added to 

 100 cc. sea water. He attempted to raise the newly fertilized 

 eggs of Strongyloccntrotns in a neutral Ringer's solution without 

 success, but found that with the addition of a small quantity of 

 KOH, or better NaHCO 3 , good larvae might be obtained. He 

 concluded that a neutral or faintly alkaline solution is necessary 

 for normal development (2). This conclusion was reached from 

 other points of view by Herbst (3) and Peter (4). 



Moore, Roaf and Whitley (5) performed similar experiments 

 with the eggs of Echinus esculentus; the addition of small amounts 



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