Some new forms of visual purple found in sea fishes with a note on the visual cells of origin

Extract

This paper records the measurement of the absorption curves of a number of new forms of visual purple which have been found among fishes. For reasons which will be given immediately it was hoped that we could correlate these results either with the habits of the species or with the microstructure of their retinae, but the attempt was not successful. We believe the results in themselves to be important because they show that light-sensitive substances of varying absorptions can be found in the retina and it may not be impossible to discover substances which form intermediate links in the perception of colour. The retinae of fishes have attracted considerable attention from histologists because of their large and easily studied visual cells and the extent of their photomechanical changes. The results reported here on the types, distribution, and behaviour of the visual cells in the species examined are not claimed to be either exhaustive or final. The histology was carried out under difficulties and it was only possible to examine a few specimens of each species. It was found, however, that where other workers have also reported on the same retina (as in the elasmobranchs, eel, trout, etc.) the observations were always in agreement.