Homology of retractile filaments of vampire squid.

The axial filament nerves of Vampyroteuthis infernalis are joined to two separate parts of the brain. One branch of the nerve, apparently efferent, arises from the anterior portion of the middle subesophageal mass, and the other, apparently afferent. enters the ventral magnocellular lobe. Since this innervation is entirely different from that of the arms, the filaments can no longer be considered homologous with the arms. The validity and primitive nature of the order Vampyromorpha, therefore, needs to be reexamined.