Inhibition of development ofPlanorbis exustus by chloramphenicol

Summary The effect of chloramphenicol (CP) on the development ofPlanorbis exustus has been studied. The antibiotic is found to inhibit cleavage at high concentrations. At low concentrations development is blocked at early gastrulation. There are indications that the effect cannot be reversed by mere transfer of the embryos into normal medium, if they have been treated for 48 hours. If transfer into normal medium is made 24 hours after commencement of treatment, development is resumed.Gastrulae developed normally even in the presence of CP. In low concentrations of CP a characteristic delay in development is observed between the trochophore and hippo stages.The significance of this developmental inhibition has been discussed in relation to synthetic processes occurring in the various phases of development.The antilytic property of CP is evident in these experiments.