46 J. WILLIAM BUCHANAN 



The data indicate that the stimulation of the cells near the 

 anterior cut surface of the piece and concerned in the formation 

 of the new head is a general protoplasmic excitation and that 

 the stimulation of the whole of the piece exclusive of these cells 

 is largely of nervous origin. 



Anesthetics alter head frequency, 1) by direct inhibition of 

 the processes of development of the cells near the anterior cut 

 surface; this inhibition decreases head frequency; 2) by inhibi- 

 tion of the increase of metabolic activity of the whole of the 

 piece after section; in pieces from certain regions this effect 

 overbalances the direct effect on the developmental processes 

 of the cells near the anterior cut surface, and in such pieces head 

 frequency is increased. 



A preliminary account is given of experiments which show 

 that head frequency can be controlled by subjecting the pieces 

 throughout the entire period of regeneration to concentrations 

 of anesthetics so dilute as not to inhibit the stimulation of section. 



The oxygen consumption of pieces subjected to weak solu- 

 tions of anesthetics rises continuously. At the end of two weeks 

 the rate of pieces in ethyl alcohol is several times that of the 

 control. The rate of pieces in chloretone, chloral hydrate, and 

 chloroform solutions is also higher than that of the controls at 

 the end of two weeks. 



BIBLIOGRAPHY 



Bellamy, A. W. 1919 Differential susceptibility as a basis for modification and 

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BiRGE, E. A., AND JuDAY, C. 1911 The inland lakes of Wisconsin. Wisconsin 

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Child, C. M. 1911a Experimental control of morphogenesis in Planaria. 

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1911b Studies on the dynamics of morphogenesis and inheritance in 

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1911c Die physiologische Isolation von Teilen des Organismus. 

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1913 a Studies, etc. V. The relation between resistance to depress- 

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