to the Lysite. Granger, Bull. ^Amer. Mus. Nat. Hist., Vol. XXXIII, 



In certain cases the paleontological evidence is in- 

 decisive, as between tlie hypothesis of successive muta- 

 tion in loco and the hypothesis of continuous evolution 

 in an unknown center of evolution followed by discon- 

 tinuous immigration of later stages into the region under 

 observation. Such a case is described by Matthew^ as 



