The structure and development of normal and mutant eyes in Gammarus chevreuxi

Abstract

It is well known that in the Amphipod Gammarus chevreuxi Sexton a great number of mutant types have been found and described during the last 20 years (of. Sexton and Wing, 1916; Allen and Sexton, 1917 , 1920; Sexton and Huxley, 1921; Sexton and Clark, 1926; Sexton Clark and Spooner, 1930). Most of these mutant types concern the eyes, which show a great variety from the normal wild type to a practically eyeless form. Although the variation is not so great as that shown by the eyes of Drosophila, it seemed to be fo interest to investigate the microscopic structure of these various types, and their development during embryonic life. The work may supplement in useful way similar studies on Drosophila, as Gammarus has an indefinite development and its embryonic life can be easily followed from step to step almost from the first cleavage until hatching, and is not interrupted by a complicated process of metamorphosis. Our first task was to investigate the microscopic structure of adult eyes. Here the particular problems were the structural basis of the mutant phenotypes:-