The innervation and general morphology of the lateralis organs of Xenopus laevis are described. Each group of organs is innervated by two large and two or fewer small fibres. Each of the large fibres gives off a branch to each of the lateralis organs in the group, but the branching of the small fibres is less regular. Each lateralis organ is therefore innervated by two large and up to two small fibres. The large fibres branch extensively at the base of the organ, the small fibres less so, and the nerve endings lie basal to or between the sensory cells. No terminal swellings could be seen. The endings of a particular fibre are not restricted to any one region of the organ.
No special function could be assigned to the dual arrangement of the innervation.
The original accounts of the structure of the lateralis organs were adequate. The recently suggested division of the supporting cells into three types is not justified.
It is probable that a cupula exists on the lateralis organs but it could not be observed.
It is suggested that the supporting cells secrete the cupula.