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Pig. 13. Curves showing the average velocity ot development of pupae 

 under different conditions of approximately constant temperature and humidity. 

 The velocities are derived, from data in Tables XII and XIII, by dividing the 

 mean pupal life in days into 270, and are shown immediately adjacent to the 

 curves. Each curve has its base on the humidity which is mean for the obser- 

 vations; this mean is shown at the left as a scale applicable to the beginnings 

 of all curves. The double squares indicate the mean points through which the 

 curves were originally drawn. The broken lines indicate the curves drawn 

 through these double squares. The solid lines, which are the curves used in 

 subsequent work, resulted from smoothing the various velocity lines of Pig. 14A. 



