SUMMARY AND CONCLUSIONS 249 



with a, and is not reached by a sliding backwards 

 down the line 0, a. 



Thus, although the most recently acquired 

 features may disappear first, degeneration is not 

 an actual retracing of steps until the point of 

 departure is reached. The degenerate condition 

 is a new point, and really the term retrogressive 

 evolution is misleading. 



