272 



THE RATE OF GROWTH 



[CH. 



Both experiments give us fairly smooth curves of growth within 

 the period of the observations; and, with a shght and easy extra- 

 polation, both curves draw to the base-hne at zero (Fig. 84). More- 



Fig. 84. Curve of regenerative growth in tadpoles' tails. 

 From M. L. Durbin's data. 



Fig. 85. Tadpoles' tails : , amount regenerated daily, in mm. 

 (Smoothed curve). 



over, if from the smoothed curves we deduce the daily increments, 

 we get (Fig. 85) a bell-shaped curve similar to (or to all appearance 

 identical with) a skew curve of error. In point of fact, this instance 

 of regeneration is a very ordinary example of growth, with its 



