THE EFFECT UPON DEVELOPING EGGS OF EXTRACTS OF EMBRYOS OF THE SAME SPECIES

1. Extracts of Arbacia larvæ in the 128-256-cell stage, in the early and in the late blastula, gastrula, and pluteus stages, when present in a sufficiently high concentration, definitely retard the development of eggs of the same species.

If these extracts are used in very low concentrations, the retardation may well lie within the limits of experimental and observational error.

2. The retardation noted is manifested slightly in the early cleavage rates, and more markedly in the later stages of development.

3. Besides retarding development, these embryological extracts often cause cytolysis, arrests of development, and a very noticeable failure of the eggs to develop beyond the early non-motile blastula stage.

4. The very evident tendency of the eggs to stop at the blastula stage suggests that possibly this stage is a stage peculiarly susceptible to the extract and characterized by a general lack of resistance.

5. It is possible that extracts made from larvæ in a certain stage differ qualitatively from those made of larvæ of an earlier or a later stage, but we do not know that this is true, nor do we know that the retardation is associated with any modification of the rate of enzyme action, or permeability, or oxidation, or any specific process. Probably it depends upon the great complexity of the protoplasmic system, and the fact that no one part of that system may be altered considerably without disturbing the equilibrium of that whole system.

6. It is not possible to say at this point that the retardation caused by the extract affects the same metabolic processes as do the KCN, CH₃COOH, NaOH, etc., but the use of the extract results in arrests and retardations of development such as are apt to be caused by these chemical agents, and the various types of malformations resulting are often similar.

7. This work does not indicate, then, either the presence or the absence of formative stuffs, but shows that under the conditions given they do not appear. Two possibilities present themselves. If formative stuffs exist, they would seem to be unable to pass into solution in sea water, in lipoid-soluble substances, and in solvents which are able to dissolve carbohydrates. Therefore, if present, they appear to be complex in character and in close association with the protein molecule. The other possibility is that these hypothetical substances may go into solution in certain solvents, but yet may not be able to register any effect upon the developing eggs, because the cell walls of the latter may not be permeable to the formative stuffs in solution.