[Cloacogenic transitional epithelium of the anal canal and Solère's theory on cloacal partitioning].

A transitional zone, between the squamous and columnar epithelium is described at the anorectal junction. Its existence, unknown in most of the Histology text books is an indirect evidence of the theory of SOLERE (1969). According to this author, there is a flattened sagittal entoblastic bud, shared by uro-genital and anal zones, achieving the closure of the cloacal cavity in its distal part. Some data which agree with this theory are discussed.