retinal growth in double dorsal and double ventral eyes in xenopus the growth of normal and surgically produced compound dorsal and ventral retinae in xenopus laevis has been studied autoradiographically following injections of 3h thymidine at stages 50 and 58 the animals were sacrificed 3 weeks after metamorphosis the histogenetic pattern of the dorsal and ventral retinal halves was different at the three time points investigated ie up to stage 50 between stages 50 and 58 and between stage 58 and 3 weeks after metamorphosis asymmetrical dorsal retinal growth occurred up to stage 50 from stage 50 onwards the retinal growth tendency reversed so that more ganglion cells were produced along the ventral than the dorsal ciliary margins the overall preponderance of ventral retinal growth was 324 in cell number and 124 in retinal length from early embryogenesis to 3 weeks after metamorphosis the characteristic histogenetic pattern of the dorsal and ventral retinal halves was maintained in an ectopic position in the compound eye indicating that this particular property of the retinal halves is intrinsically determined