Development and metamorphosis of the larvae of Ascidia malaca in different experimental conditions.

In larvae of Ascidia malaca that have developed in sea-water without sulphate ions, the cells of the caphalo-ventral region are devoid of sulphated mucopolysaccharides, and the chordal and muscular cells of the tail turn out to be altered; after metamorphosis no adhesive ampullae appear. The addition of cysteine to water lacking sulphate ions leads to a normal synthesis of sulphated mucopolysaccharides in the cells of the cephalo-ventral region, and to a normal secretion of matrix by the chordal cells; but the larvae do not regain the ability to swim. The addition of N-dichloroacetyl-DL-phenylalanine to sea-water does not alter the synthesis of sulphated mucopolysaccharides in the cells of the cephalo-ventral region, but, probably by acting as a competitive inhibitor of phenylalanine, it causes alterations in the muscular cells of the tail.