THE CELLULAR ELEMENTS IN THE PERIVISCERAL FLUID OF ECHINODERMS

¹ BIOLOGICAL LABORATORY, WESTERN RESERVE UNIVERSITY

From a comparative study of the cellular elements in the perivisceral fluid of a representative group of Echinoderms found in the vicinity of the Puget Sound Biological Station the following conclusions have been reached:

1. The leucocytes are constant in the perivisceral fluid of the Echinoderms.

2. The leucocytes in all of the Echinoderms studied are phagocytic and thromboblastic and in some species appear to be scleroblastic and associated with the replacement of resected skeletal areas.

3. Hemocytes (cells with hemoglobin) are found only in certain of the Holothuroidea and are correlated with the development of a highly muscular body.

4. Modifications of the breathing organs have apparently no effect on the cellular contents of the perivisceral fluid, so that no specific oxygen-carrying cells are developed in those forms with a rigid non-muscular body wall despite the limitations of the breathing organs.

5. Of the "ambocytes with spherules," those with colorless spherules are present in the Ophiuroidea, Echinoidea and Holothuroidea and are predominant in the last class. "Ambocytes with red spherules" are present in the Echinoidea, where the size and number present is correlated with the depth of color of the body wall.

6. Vibratile corpuscles are present in the Ophiuroidea, Echinoidea and in Stichopus californicus alone of the Holothuroidea studied. In the latter species they are pigmented and are regarded as cells which function as do the hemocytes in other muscular-bodied Holothuroidea.