CELL TYPES AND CLOTTING REACTIONS IN THE ECHINOID, MELLITA QUINQUIESPERFORATA

Abstract

There are 2 types of leucocytes and 4 types of amoebocytes in the perivisceral fluid of the sand-dollar Mellita. Both types of leucocytes and an amoebocyte containing a brown fluid and scattered granules are phago-cytic. Fat is present in amoebocytes with red spherules, but is not normally present in other cell types. When emulsions of olive oil and egg yolk are injected into the perivisceral cavity, droplets are taken in by the leucocytes alone. Clotting involves the cellular elements of the perivisceral fluid, but does not include the plasma. When the perivisceral fluid is shed the leucocytes with large pseudo-podial lobes produce a sticky substance to which moving amoebocytes and other leucocytes adhere, and finally become entangled in small clumps. As the end point is reached there is a general contraction of the clump, entangled amoebocytes become spherical, and their spherules break down. Isotonic solns. of KCl and CaCl2, a hypertonic soln. of NaCl and 5% C2H5OH decrease the time of clotting. Nacitrate and K-oxalate increase the time of clotting, whereas MgSO4 retards clotting indefinitely.