HEAT PRODUCTION BY THE EGGS OF ARBACIA PUNCTULATA DURING FERTILIZATION AND EARLY CLEAVAGE

The heat production of the eggs of Arbacia punctulata has been measured before, during, and following fertilization, through development into the eight cell stage. It has been found that the rate of heat production at the instant of fertilization is ten to twelve times that of the unfertilized egg. After fertilization the rate of heat production decreases constantly for twenty minutes, when it reaches about 65 per cent. of the value at fertilization, and remains constant until the first cleavage, at about 50 minutes after fertilization. At the first cleavage the rate drops suddenly by more than 10 per cent., and then remains constant until the eggs are in the eight cell stage, which is as far as the work has been carried. The rate of heat production of the unfertilized eggs was found to be about 0.08 calories per hour per million eggs, and that of the fertilized eggs about 0.52 calories per hour per million eggs after the one cell stage.

An experiment on Arbacia sperm indicates that when placed in contact with sea water, its heat production is similar to that of an exothermic chemical reaction of the first order.

The suggestion is offered that the heat evolution occurring immediately upon fertilization is the result of an oxidative process which takes place in the cortex (chiefly) of the egg and which leads to the elevation of the fertilization membrane.