It is a well-known fact that individual cells carry electric charges a t their surfaces. This is demonstrable by the cataphoretic method, and charges of blood cells and bacteria have often been measured. On the contrary, the surface charge of marine egg cells is not known, in spite of the fact that these cells have been widely studied from other standpoints.
There are, it is true, a few scant observations concerning egg cells, but these are at best roughly qualitative. Inasmuch as bacteria and blood cells are more or less inert and specialized types of cells whereas marine eggs are more active and thus more interesting in many respects, it is important to discover, if possible, the nature and the magnitude of the surface charge of these cells.
McClendon ('14) after making a qualitative study, concluded that the egg jelly of the sea urchin (Toxopneustes) was negatively charged while the perivitelline fluid of the fertilized egg must be positively charged, and he developed the theory that the fertilization membrane might be the precipitation membrane between two oppositely charged colloids (a theory now generally abandoned). On the other hand Szent-Gyorgyi ( '21) using a cataphoresis chamber of his own type, contended that sea urchin eggs (Echinus vulgaris) did 'This and a second paper constitute a thesis presented to the faculty of the Graduate School of the University of Pennsylvania in partial fulfillment of the requirements f o r the degree of Doctor of Philosophy.