“…In regard to the effect of carbon monoxide on unfertilized sea urchin eggs, Rothschild (1949) was able to demonstrate a photo-reversible inhibition of O,-uptake when account was taken of a CO-induced stimulation and a lightinduced inhibition of respiration. Concerning the effect of temperature on respiratory rates, further measurements (Tyler and Humason, 1937;Borei and Lybing, 1949) have shown no significant differences between unfertilized and fertilized sea 'rchin eggs. -Permanent address : Department of Zoology, University of Cambridge, Cambridge, England.…”