Developmental modification and elimination of the larval stage in the ascidian, Corella willmeriana

Abstract

Abstract The eggs of Corella develop in the atrial chamber of the parent at a pH below that of normal sea‐water (pH 7.4 ±). When removed to normal sea‐water in early stages and under certain other experimental conditions, larval development is more or less inhibited, the tail being most inhibited, the dorsal region somewhat less. The free larval stage may be eliminated and later development and metamorphosis may proceed normally to an advanced stage in the chorion and give rise to normal ascidians. The region most inhibited are, in general, those which possess the highest reducing power, as indicated by KMnO 4 . Experiments made in the attempt to control development all agree in indicating that the early stages are adjusted to a certain CO 2 concentration approximately that of the atrial chamber and presumably near that of the body. Solutions of the same pH may or may not inhibit development according to their CO 2 content. The tail, the region of highest reducing power in the embryo during its development, is most inhibited; the dorsal region, the next most rapidly reducing region, is next in degree of inhibition. All differences in reducing power disappear when, or soon after, the animals are killed by other agents before treatment with KMnO 4 .