Fig. 4. The relationship between the number of hair cells (each with one kinocilium) and the flexural stiffness of the cupula [(EI)_cup]. Mean values (±1s.d., numbers next to points denote the sample size for each point) are shown for neuromasts of a variable number of hair cells. The trend line represents a significant (P<0.015) weighted linear regression that suggests that most of the variation (r²=0.81) in flexural stiffness is related to the number of hair cells. This trend was predicted by our hypothesis (Eqn 5), which interprets the slope of this line (2.4x10^–21 N m²) as the stiffness generated by a single kinocilium.