Fig. 1. Photolysis of caged calcium. An image of a pinhole with a diameter of 400 µm was focused onto the specimen. (A) 300–400 nm UV light was collected by a UV-transmitting objective lens to produce a small UV spot on the specimen. (B) A Paramecium caudatum cell. Approximately 15 000 cilia are present on the cell surface. The length of each cilium (approx. 10 µm) is equivalent to the diameter of the UV spot (A) in which photolysis was induced. Bar, 30 µm.