The eggs of A. punctulata have a high temperature coefficient in the resting state: Q 10 = 4.1. On fertilization and on cytolysis the temperature coefficient falls to less than half the resting value: Q 10 = 1.8 and 1.9 respectively. The factor by which oxygen consumption increases on fertilization is a variable, its magnitude depending on temperature as well as on egg species. It is nearly ten times greater at 11°C. and only double at 29.9°C. By extrapolating to 32°C. there would be no increase on fertilization. Critical thermal increments common to many oxidations, 6,500, 10,800, and 12,500, have been found. The possible significance of these results is discussed in relation to the catalytic mechanisms and structural organization of the egg cell.

Methods used in preparing Arbacia eggs for respiration studies, in carrying through the manometric determinations, and in estimating egg quantities have been reexamined. Discrepancies in previous results are almost entirely due to a steady error in measuring egg volume by centrifuging. Volumes so obtained averaged 80 per cent too high. The respiration of unfertilized eggs of Arbacia punctulata at 21°C. is 0.9 c.mm. O 2 per hour per 10 c.mm. of eggs.