i c h i g m
Earlier study has shown that all agents which cause artificial parthenogenesis in the sea-urchin egg produce a coagulation in the cytoplasm (Heilbrunn, '15). This does not mean that all types of coagulative change cause the egg to begin its development, for, as is fairly obvious, some coagulations cause only death.
It is well known that other eggs differ from the sea-urchin egg in their susceptibility to various parthenogenetic agents, and it is of interest to study these eggs and t o compare them with each other and with the sea-urchin egg. It is of particular importance to include eggs in different stages of maturation. The sea-urchin egg is already mature when it is shed into the sea-water7 but many eggs at the time of fertilization have not completed the first maturation division and still retain the first maturation spindle. The behavior of these eggs is particularly interesting, for they already have a spindle, and it is difficult to understand what effect a coagulation might have upon them. Other eggs are in the germinal vesicle stage at the time the sperm enters, and yet they, too, may be made to start their development artificially.
I n the second paper of this series I tested the effect of all parthenogenetic agents on one egg. I n the present study I have attempted to determine the effect of a single parthenogenetic agent on several types of eggs.
Of all parthenogenetic agents heat is perhaps the most generally applicable. Heat parthenogenesis has been described 243