' Myriads of types, unready and conservative, have passed out of being ; that which 

 they had, but did not improve, has been taken from them, whilst others, by steady 

 improvement of what they had, have had more and more hfe given to them. But not 

 always by slow, steady increment " during long ages," has the advance been made. 

 Nature does, now and then, make amazing leaps, certain types taking on sudden 

 metamorphosis, and, in the fraction of a lifetime, the low is transformed into the high.' 

 Professor W. Kitchen Parker, On Mammalian Descent, p. 93. 



