The Infraorbital Canal, Its Lateral-Line Ossicles and Neuromasts, in the Minnows Notropis volucellus and N. buchanani

To determine the role of the neuromast in bone formation, histological and osteological studies were made of the infraorbital canal in Notropis volucellus and N. buchanani. Special emphasis was placed on the histological structure of the superficial and canal organs. The infraorbital canal in N. volucellus is complete or incomplete, while that in N. buchanani is absent or rudimentary. The number of infraorbital ossicles in N. buchanani has been reduced from five, as in N. volucellus, to two or three. In both species the sustentacular cells of the neuromasts extend upward to surround the cells. The cells are strongly polarized and apically bear two sense hairs each. In N. volucellus a cellular enlargement in the innervating nerve of the canal neuromast was described. It was concluded that lateral-line bones are of composite origin, part stemming from anasmestic forces and part from the tropic activities of the neuromast.