Politically, indeed, the whole period was one of retrogression and stagnation.
As a matter of fact, as far as modern Europe is concerned, there has twice been a progression, separated by a period of retrogression, and it is to the latter that Bucher's picture of the agricultural and strictly protectionist town (the geschlossene Stadtwirtschaft) of the 14th and r 5th centuries belongs, while Sombart's notion of an entire absence of a spirit of capitalistic enterprise before the middle of the 15th century in Europe north of the Alps, or the 14th.
The transition from the medieval to the modern order was now secured if not accomplished, and a Rubicon had been crossed from which no retrogression to the past was possible.
With certain modifications in principle not very important, but characterized by much more elaborate detail, Aldrovandus adopted Belon's method of arrangement, but in a few respects there is a manifest retrogression.
He also demonstrated that mutations have this special or distinctive character, that they repeat in the same direction without oscillation or retrogression.