Natale: Two morphologically distinct life stages of the same organism

This is an example of different life stages of a Rana sylvatica.  They were both photographed at 42°14'11.98" -71°37'49.87".  In the left picture, a late tadpole can be seen.  It has all four legs but it still also has a long tail from when it was a tadpole.  In the right picture a frog is visible.  It has all four legs and all visible signs of a tail are missing.  In the life stages of a Rana sylvatica, it goes from an egg, to a tadpole without legs, to a tadpole with legs, to a frog.