PLATE I. 



FIG. I. Embryo of Porpoise to illustrate form of Tail. 

 (From Kiikenthal.) 



FIG. 3. Hand of Beluga, showing com- 

 mencing bifurcation of finger. 

 (From Kiikenthal.) 



FIG. 2. Hand of Balanoptera muscitliis, 

 showing disappearing ringer. 

 (From Kiikenthal ) 



[ To face page g. 



