Waagen's law of mutation, or the appearance of new parts or organs so gradually that they can be perceived only by following them through successive geologic time stages, appears to be directly contradictory to the saltation principle; it is certainly one of the most firmly established principles of palaeontology, and it constitutes the contribution par excellence of this branch of zoology to the law of evolution, since it is obvious that it could not possibly have been deduced from comparison of living animals but only through the long perspective gained by comparison of animals succeeding each other in time.
Phyletic gaps began to be filled in this general way, however, by discovery, especially through remarkable 1 The Dutch botanist, De Vries, has employed the term in another sense, to mean a slight jump or saltation.
Saltation The genesis of powder snow avalanches is also thought to sometimes arise from a saltation layer on the surface of a dense avalanche.
Saltation cannot be initiated within the vegetation, because of the zero wind velocity at the surface.