Abstract
The hemoglobin of the "thin" sibling species of Thyonella gemmata (phylum: Echinodermata; class: Holothuria) has three electrophoretically distinct polypeptide chains. In "stout" sibling species of T. gemmata there are only two chain types. These results account for the greater number of multiple hemoglobins in "thins" than in "stouts," as well as for differences in the amounts of some of the multiple hemoglobins when comparisons are mnade of hemolyzates of erythrocytes from the water vascular systemn and from the main body cavity of the "thin" but not the "stout" sibling species.