Morphological strategies for inflectional exponence have traditionally been associated with different stages in the evolution of languages. Moreover, the so-called morphological cycle (or the typological cycle in morphology) is claimed to involve a unidirectional sequence of changes that leads from isolation to agglutination (separative exponence in inflection) and subsequently to fusion (cumulative exponence). But this rigid schema happens to exclude a wealth of diachronic developments that are solidly attested in the history of various languages: the shift from cumulative toward separative exponence perhaps constitutes the strongest challenge to the unidirectionality hypothesis implied by the classic typological cycle. Here I survey the data illustrating agglutinative developments inside fusional systems, a task that first requires a canonical definition of morphological techniques. Then the mechanisms underlying this significant typological change are classified and analyzed in detail. The final part of the article is devoted to discussing the possible causes behind the reversal of the morphological cycle. The diachronic evidence at our disposal points to a rather clear differentiation between the language-internal causes that seem to determine the shift from agglutinative to fusional structures and the language-external causes (contact influence of a particular kind) that commonly lie behind the reverse morphological change.