422 HENRY C. TRACY. 



Schwartze, E. W. 



'22 Functional Evidence of the Phylogeny of the Nervous System as Shown 

 by the Behavior and Resistence of the Developing Rat to Strychnine. 

 Jour. Pharm. and Exper. Therap., XIX., p. 237. 



Shelford, V. E. 



'23 The Determination of Hydrogen-ion concentration in connection with 

 Fresh Water. Biological Studies, Bull. Nat'l Hist., Illinois, Article IX., 

 Vol. XIV., p. 379. 



Smith, H. W., and Clowes, G. H. A. 



'24 The Influence of Carbon Dioxide on the Velocity of Division of Marine 

 Eggs. Amer. Jour. Phys., LXVIII., p. 183. 



Stockard, Charles R. 



'21 Developmental Rate and Structural Expression. Amer. Jour. Anat., 28, 

 p. 115. 



Waller, A. D. 



'96 On the Influence of Reagents on the Electrical Excitability of Isolated 

 Nerve. Brain, Vol. XIX., p. 43. 



Wintrebert, P. 



'14 Sur le determinisme des premiers mouvements et specialement leur adapta- 

 tion au volume et a la forme de 1'oeuf chez les vertrebres inferieures. 

 Comp. Rend. Soc. de Biol., 76. 



'20 La contraction rythme aneurale des myotomes chez les embryons de 

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EXPLANATION OF TABLES AND CHARTS. 



Charts I. to V. are records of specimens just hatched, bclore the beginning of 

 respiration. 



Charts VI. to XI. are records of specimens at the beginning of the free swimming 

 stage. 



Chart XII. is the combined record of the movements of the just hatched larvae 

 under all concentrations of COj. 



Chart XIII. is the combined record of the movements and respiration rate of 

 the free swimming larvae under all concentrations of COa. 



Two minute spaces are marked off on the horizontal base line: height of the 

 line indicates the average amount of movement (estimated as described on p. 10) 

 made in each minute of the two-minute period by the specimens in each concentra- 

 tion of COj. The average amount of movement each minute under normal condi- 

 tions for the time observed (15 minutes to i hour) is indicated by the arrow at 

 the beginning of each chart, marked A. N. M. The arrow marked A. M. R. 

 indicates the average movement per minute when the larvae are returned from the 

 acidulated water back to the normal. 



In Charts VI.-XI. and XIII. the respiration record of the free swimmers is 

 superimposed on the movement record (respiration not being established in the 

 just hatched larvae). The height of the short horizontal line in each two minute 

 space indicates the number of seconds (usually the average of three observations 

 in each minute) taken for 10 respiratory movements (average for all the specimens 

 of each concentration of COi). Hence a drop in the line means increased respira- 

 tory rate, and vice versa. The observed normal rate (average for each minute) is 

 indicated at the beginning of each chart by an arrow marked A. N. R. 



