Distribution of photoreceptors inducing ciliary reversal and swimming acceleration in Blepharisma japonicum

The distribution of photoreceptors was examined with respect to those initiating ciliary reversal and those inducing acceleration of swimming. Ciliary reversal was caused when a light stimulus was applied to the anterior end of the animal; the response did not occur when the light was applied to a region within the posterior three‐fifths of the animal. On the other hand, acceleration of swimming was induced by light application to both anterior and posterior fragments. These differences in response suggest that the photoreceptors initiating ciliary reversal are different from those inducing acceleration of swimming.