Electrical characteristics of Triturus egg cells during cleavage.

The membrane potential in the blastomeres of dividing Triturus egg cells increases progressively from the first cleavage to the late morula stages. Both the animal and vegetal poles show the same increasing trend in potential; there is no significant potential difference between them. Upon first cell cleavage, the total resistance of the egg cell surface in contact with the exterior decreases to about one-tenth of its value before cleavage, and then remains rather constant up to the late morula stage. The specific resistance of this membrane surface drops rather abruptly upon first cleavage, and rises progressively during the morula stage. The resistance of the junctional membrane surface of the blastomeres, that is, the membrane formed at the former planes of cleavage, is small in relation to that of the cell surface in contact with the exterior. As a result, the blastomeres are electrically coupled throughout all stages of embryonic development examined.