The Spectral Sensitivity of the Echinoid Diadema Antillarum Philippi

Abstract

1. The spectral sensitivity of Diadema antillarum has been determined using as an index the spine response to shadows cast on the internal or extenal surface of the test. 2. With shadows cast on the internal surface sensitivity is consistently greatest at 465 mµ. On the external surface sensitivity is usually greatest at either 465 or 475 mµ. 3. The action spectrum is narrow and resembles some of those obtained from the frog's retina 4. There is as yet insufficient evidence to indicate that the abundant naphtha-quinone pigment (λ_max. 463) oaming in this urchin, is involved in photoreception.