CERTAIN CHEMICAL FACTORS INFLUENCING ARTIFICIAL ACTIVATION OF NEREIS EGGS 1 -2 PAUL G. LEFEVRE Marine Biological Laboratory and Zoological Laboratory, University of Pennsylvania INTRODUCTION Stimulation must involve physicochemical changes within cells, and the nature of such changes has been the subject of much investigation, both experimental and speculative. The process of fertilization, and the closely related process of activa-tion in artificial parthenogenesis, have attracted special attention ; and evidence has been presented for a number of interesting interpretations of this type of activation. This report concerns a group of experiments indicating a peculiar relation of picric acid to the artificial activation of the eggs of Nereis. The proper interpretation of these experiments might contribute to the understanding of the stimulatory process. The experiments described developed from incidental observations in connection with heat-activation, during investigations concerned with the more general question of the mode of action of heat on protoplasm. The peculiarities of heat-activation of the unfertilized Nereis egg were first de-scribed by Just (1915), who was able to interpret all his data in harmony with Lillie's "fertilizin" theories. In particular, Just attributed the gradual loss of sensi-tivity to heat, in eggs left standing in sea water, to the diffusion from them of some fertilizin-like substance, essential to the activating process. Heilbrunn (1925) took exception to this notion, in suggesting a "colloid chemical" interpretation of heat-parthenogenesis ; he believed the decrease in sensitivity to heat might be due to the gradual loss of CO 2 from the medium, resulting in alkalinization of the intracellular fluid. Heilbrunn described three experiments in which the addition of 2^ volumes per cent of n/10 HC1 to old insensitive egg-suspensions restored their original sensi-tivity to heat. To reveal a possible general relation between intracellular acidity or carbon dioxide concentration and the response of cells to increased temperatures, these three observations were extended. Heilbrunn's findings were in part confirmed ; but with the accumulation of large numbers of experiments, considerable variation was encountered in the response of the heat-sensitivity of the eggs to increased CO 2 concentration through acidification of the sea water. Though such pronounced ef-fects as described by Heilbrunn were often repeatable, as many batches of eggs seemed totally unresponsive to the same treatment. In the course of testing several organic acids in this connection, however, the anomalous properties of picric acid (2, 4, 6-trinitrophenol) came to light. Extension of these properties to processes of activation by means other than heat was then attempted. 1 This study was carried out under the direction of Dr. L. V. Heilbrunn. I gratefully ac-knowledge his helpful suggestions throughout the investigations, and his valuable assistance in interpreting the results. 2 A dissertation submitted to the faculty of the Department of Zoology of the University of Pennsylvania in partial fulfillment of the requirements for the degree of Doctor of Philosophy. 144
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