ABSTRACT
In the previous papers (Carter, 1930, 1931) results were recorded which led to the conclusion that the egg-secretions of these species of Echinus contain a substance which is similar to thyroxine in its action upon the activity of the sperm. The experiments to be discussed in the present paper were undertaken with the object of observing whether thyroxine is also able to produce effects in the cytoplasm of the egg similar to those normally produced by the secretions.
These substances were des-iodo-thyroxine, tyramine, di-iodo-tyrosine, tyrosine, tryptophane, potassium iodide and iodate, and free iodine. The methods by which solutions of these substances were made have been described in the previous paper (1931, p. 179). The solubility of thyroxine in sea-water has also been discussed in that paper. The concentrations of thyroxine given in this paper refer, as in the previous paper, to the amount of the drug added, not to the concentration of dissolved thyroxine present, which is always much less.
