The electrophysiology of the retina ofPeriplaneta americana L.

Retinula cells ofPeriplaneta in the same state of morphological adaptation differ among themselves in absolute sensitivity by up to 1 log unit (tenfold).Morphologically dark-adapted retinula cells are, on average, ten times as sensitive as light-adapted cells to light on the optical axis.All retinula cells are about 5 times as sensitive to plane polarized light in the plane of its optimum effectiveness as in the orthogonal plane.Retinula cells fall into two groups with optimum plane of polarization 90 ° apart, corresponding with the 2 planes of rhabdomeric microvilli.