Occurrence of Triple and Quadruple Cones in the Retina of the Minnow (Phoxinus laevis)

Abstract

TRIPLE cones have previously only been observed in the retinæ of a frog, Rana temporaria ¹, and of a gecko, Aristelliger praesignis ², and in both these animals they are rare and atypical. I have examined many retinæ of trout, Salmo trutta, of all ages, and I have found a considerable number of triple cones which, from their distribution in the cone pattern, appear to be anomalous double cones. In the minnow, however, triple cones are abundant and predominate in most regions of the retina, and quadruple cones are numerous enough to suggest that they may have a significant function.