JL50 



matured. If such lots of eggs be shaken violently for a few minutes 

 before the spermatozoa are added, a much larger percentage of the 

 eggs will develop. In one case recorded where the eggs were shaken 

 forty-five eggs segmented and only eight remained unsegmented, while 

 similar eggs not shaken gave only twenty-six eggs segmenting out of 

 one hundred and eighty unsegmented. This is not due to removal of 

 the egg membrane allowing the spermatozoa to enter more readily, 

 because as Mr. A. P. Mathews pointed out to me, a much larger per- 

 centage of polar bodies are extruded from the shaken eggs than from the 

 normal unshaken eggs, and this I have found will take place whether 

 spermatozoa have entered or not. 



After a few minutes of shaking the eggs seem to loose their nuclei, 

 but a study of stained preparations shows that the shaking has only 

 caused the nuclear membrane to disappear (?), so that the chromatin 

 and nucleolus are set free in the protoplasm. 



Has the breaking down of the nuclear membrane pre- 

 cipitated the ripening of the eggs? Similar results follow when the 

 immature (?) Arbacia eggs are shaken, with the exception that the 

 nuclear membrane does not seem to break down in these eggs except 

 very rarely. 



In both cases in some way or other the shaking brings about the 

 maturation of a larger percentage of unripe eggs — a fact remarkable 

 in itself, even if we cannot understand how it comes about. 



III. 



It was noticed that after the star-fish (Asterias) eggs were shaken 

 and fertilized with Arbacia sperm, a small percentage of embryos de- 

 veloped, but similar eggs would give nearly the same small percentage 

 when no sperm was added, and moreover normal eggs not fertilized 

 or shaken gave the same result. Undoubtedly the sea-water entering 

 the laboratory through the pipes always contained a small percentage 

 of the spermatozoa of Asterias. Similarly with Arbacia. Among the 

 embryos a few in the crossed experiments differed from the 

 normal. The experiments were repeated and precautions "taken to 

 prevent contamination of the water and also to eliminate sources of 

 error by check experiments. All water used was heated to 70 ° C and 

 allowed to cool. All dishes were soaked in fresh water and extreme 

 care taken with pipettes and other instruments used. The following 

 gives the result of the most satisfactory experiment. 



First experiment. Normal eggs of Asterias fertilized by Asterias 



