  A detailed study of nearby, morphologically normal Sa galaxies reveals that
about half show some spectrocopic evidence for kinematically distinct
components despite their undisturbed optical appearance. In eight of nine
objects mapped in the 21 cm HI line, the HI distribution extends far outside
the optical disk and warps of the HI disk are complex. The multiwavelength
evidence can be interpreted in terms of the kinematic "memory" of past minor
mergers in objects that otherwise exhibit no morphological signs of
interaction.
