THE INFLUENCE OF HYDROGEN ION CONCENTRA- 

 TION ON UNFERTILIZED ARBACIA, ASTERIAS ANT) 



CHJETOPTERUS EGGS. 



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



(From the Lilly Research Laboratory, Indianapolis and the Marine Biolog- 

 ical Laboratory, Woods Hole.) 



In a previous paper the writers briefly reported experiments on 

 the effects of increased H-ion concentration in sea water on the 

 fertilization and development of the normally fertilized eggs of 

 the star fish (Astcrias forbesli) and sea urchin (Arbacia punc- 

 tulata) ( i ) . This work has since been repeated and extended in 

 several directions and more complete reports on these subjects 

 are now ready for publication. The experiments to be reported 

 in this paper deal with effects of acid and alkaline sea water on 

 the rg.te. of ageing of unfertilized Arbacia, Asterias and Cliatop- 

 terus-^gg-s,- and with the artificial activation of Clicetopterus eggs 

 by acid sea wateV. These experiments, beside affording a neces- 

 sary basis for further studies of the influence of variations in H- 

 ion concentration on the fertilization and developmental processes, 

 furnish important information on the relation of the physiological 

 activity of the egg cell to its environment. 



PREPARATION OF ACID AND ALKALINE SEA WATER. 



Certain of our experiments, which will be described in a sub- 

 sequent paper, have shown that CO 2 exerts a profound effect, 

 distinguishable from the effects of H ions, on many of the physi- 

 ological processes of marine eggs. Since sea water naturally con- 

 tains a considerable quantity of combined carbonic acid, it is 

 necessary in all experiments designed to observe the effects of 

 H ions per se to work with sea water from which the CO 2 has 

 been removed. The CO.,-free sea water used in these experiments 

 was prepared as follows : To each liter of fresh sea water was 

 added 5 cc. of N/2 HC1 and 5 cc. of N/io NaH 2 PO 4 ; this mix- 

 ture was aerated with a water vacuum pump over night. No pro- 



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