ABSTRACT
When sea-urchin eggs are fertilized an acid, the fertilization add, diffuses out of them into the surrounding sea water. A claim has recently been made that the fertilization add may be lactic acid, which is oxidized shortly after its production.
There is no significant difference between the amounts of lactic add produced by unfertilized and just-fertilized eggs of Echinus esculentus.
The amount of lactic add produced by fertilized eggs of this species is too small to explain the evolution of CO2 observed when the eggs are fertilized in manometer vessels.
The sea water round just-fertilized eggs was found to contain markedly less bicarbonate than the sea water round unfertilized eggs, confirming that an acid diffuses out of the eggs after fertilization.
There is some evidence that the small quantities of lactic add produced by unfertilized and just-fertilized eggs of this spedes do not diffuse into the surrounding sea water.
It is conduded that the fertilization add is not lactic add.
Misprinted on p. 269 as ‘mg. lactic acid In a letter dated 11 June 1958, Dr Aketa kindly gave me some information which indicates that 120 μg. lactic acid/mg. protein N is equivalent to about 1·4 mg. lactic acid/106 eggs, or 10 mg. lactic acid/100 mg. N, which is ten times Runnström’s value, cited by Örstrom & Lindberg (1940).
Dr H. Barnes kindly estimated the total N content of these eggs for me and obtained the value 67 mg. N/106 eggs. Ballentine (1940) found 5·8 mg. N/106 eggs of Arbacia punctulata, whose radius 37μ M (Harvey, 1956). The ratio of these values, per ml. of eggs, is 1·01.
