STUDIES IN THE PIGMENTARY SYSTEM OF CRUSTACEA

I. COLOR CHANGES AND DIURNAL RHYTHM IN LIGIA BAUDINIANA

¹ From the Bermuda Biological Station for Research, Inc., and the Biological Laboratories, Harvard University

1. The bodily changes in color of Ligia baudiniana upon black and upon white backgrounds are due chiefly to a dispersion and concentration of pigment granules within melanophores.

2. When the animals are kept in constant darkness, there is a diurnal rhythm in pigmentary activity, the isopods being dark during the day, and light at night.

3. Injection of aqueous extracts of heads into the body spaces of dark Ligia brings about lightening in color by a concentration of the melanophores.

4. Extracts from the heads of dark and of light specimens in the two conditions of diurnal rhythm are practically equally effective in concentrating the melanophores of dark isopods. It may be concluded from this that the diurnal pigmentary activity is not due to a cycle of exhaustion and elaboration of secretory material in the endocrine gland controlling the color changes.