NERVE-CONDUCTION IN CASSIOPEA XAMACHANA. 



By Alfred Goldsborough Mayer. 



It is the author's privilege to acknowledge his indebtedness to kind 

 friends for advice and aid : To Professor George A. Hulett, of Prince- 

 ton University, for having had prepared in his laboratory the con- 

 ductivity water used in this research; to Professor J. F. McClendon, of 

 the University of Minnesota, for valued advice and aid, and to Professor 

 L. R. Cary, of Princeton, for permission to make use of his recent deter- 

 minations of the rate of nerve-conduction at different temperatures. 

 By means of the generous interest of Professor E. G. Conklin and the 

 authorities at Princeton I have enjoyed the excellent facilities afforded 

 by the Biological Laboratory in Guyot Hall, wherein the kymograph 

 records taken at Tortugas were studied and the results tabulated. 



METHODS AND CORRECTIONS. 



The object of this research was to obtain an accurate quantitative 

 determination of the rate of nerve-conduction in natural and in diluted 

 sea-water at constant temperature, and also to estimate the effects of 

 various artificial sea-water solutions containing all or some of the 

 sodium, magnesium, calcium, and potassium cations of sea-water. 

 The effects of temperature upon nerve-conduction are also of great 

 importance. 



These studies were carried out in June and July 1916, upon Cassiopea 

 xamachana, a rhizostomous scyphomedusa which is abundant in the 

 salt-water moat surrounding Fort Jefferson at Tortugas, Florida, and 

 is also conmion upon the bottoms of many of the shallow, semi- 

 stagnant lagoons of the West Indian region. It is thus accustomed to 

 a considerable range both in saUnity and temperature, and being 

 infested with commensal plant cells, it is in some measure independent 

 of the oxygen-supply of the surrounding water, and even pulsates at a 

 nearly normal rate in sea-water which has been deprived of air by 

 boiling. The medusa thrives in confinement in glass aquaria and can 

 be maintained alive in the laboratory for months while experiments 

 are being performed upon it. Thus it is one of the most favorable of 

 marine invertebrates upon which to conduct physiological studies. 



An aboral view of Cassiopea xamachana is shown in figure 1 , plate 1 ; 

 figure 2 is an oral view of the subumbrella with the stomach and 

 mouth-arms removed, and in figure 3 we see an annulus made by two 

 circular cuts, one removing the marginal sense-organs and the other 



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