Some Physicochemical Properties of Dissociated

It has been known since Wilson's discovery (I) that dissociated ceils of Microd~a come together and form aggregates, which by further transformation develop into new sponges. Similar processes were observed in fresh water and in calcareous sponges (2, 3), and in hydroids and alcyonarians (4, S). Recently one of us (6, 7), in studying the behavior of dissociated cells of Microdona, found that the formation of aggregates is due to the ameboid movement of so called arch~o.cytes, that is, unspecialized cells of the sponge mesenchyme, which upon separation creep in various directions and coalesce with other cells of the same species which happen to lie on their route. AccordLug to these observations, aggregation is easily affected by changes in the surrounding medium. In pure isotonic solutions of NaCI or KC1 the ameboid movement is entirely inhibited, and the addition of at least one of the alkaline earth metals, either Ca or Mg, is necessary to produce the aggregation of cells. The addition of acids or bases to a suspension of cells also causes significant changes in their behavior, inhibiting their movement and changing the adhesive properties of the protoplasm. In mixed suspension, the cells coalesce only with cells of their own species, forming separate aggregates; whale in alkaline sea water the Microdona aggregates become surrounded by the Cliona cells. The present investigation is an attempt to deal in a quantitative manner with the equilibrium relations involved between the cells of two siliceous sponges, Microciona proHfera Vex. and Cliona celata Gr., and acid or base. 239