Neuromast-centered canal morphogenesis and fusion of adjacent canal segments. A) Stages of neuromast-centered canal morphogenesis (Stages I-IV [29, 31]): Stage I – neuromast found in general epithelium, Stage IIa - neuromast sinks into depression, Stage IIb - neuromast in groove with ossified canal walls forming on either side of neuromast, Stage III - neuromast enclosed by soft tissue canal roof, Stage IV - neuromast enclosed in canal and canal roof ossified over neuromast. Canal morphogenesis continues with the gradual fusion of adjacent canal segments. Adjacent canal segments grow toward one another (B) and make contact (C). The two adjacent segments fuse (D), leaving a pore between them (E), thus forming a continuous lateral line canal. Black = bone, Gray = general epithelium and neuromasts.