DEVELOPMENT OF PIGMENT IN THE LARVA OF THE SEA URCHIN, LYTECHINUS VARIEGATUS

¹ Department of Zoology, Florida State University, Tallahassee, Florida

1. A pigment having the properties of echinochrome is synthesized in the embryo of the sea urchin Lytechinus variegatus. Differentiation of the echinophores and synthesis of the echinochrome begins at the gastrula stage.

2. Echinophores differentiate from the veg₁ cell layer of the embryo, become amoeboid and migrate into other ectodermal regions.

3. Echinophore differentiation appears to depend upon a normal relation of the "double gradient" system of the embryo. Since echinophores were produced in exogastrulae, normal juxtaposition of the germ layers is not essential.

4. The sperm nucleus was found to have no essential role in the pigmentation process. Pigment formed according to the maternal pattern in hybrid and parthenogenetic embryos.

5. Of a variety of chemical substances tested, including several respiratory and other inhibitors, only those agents which inhibited gastrulation of the embryo caused failure of pigment formation.

6. Echinochrome synthesis is apparently related to protein synthesis in the embryo.