The vestibular apparatus of the opossum (Didelphis virginiana) prior to and immediately after birth.

The vestibular apparatus of the opossum was examined shortly before and immediately after birth. A band of about 20 sensory cells was observed within the forming utricle by 24 h prior to birth. Stereocilia projecting from the apices of the sensory cells appeared intimately associated with a well-defined population of overlying otoliths. These morphological observations suggest that a functional utricle may be present at the time of birth and together with other senses (tactile, olfaction) may aid the newborn of this species in its migration from the birth canal to the pouch.