360 ALVALYN E. WOODWARD AND FLORENCE S. HAGUE. 



cytolysis were obtained by Loeb, 1 McClendon, 2 and Glaser, 3 in 

 Arbacia eggs, by placing them in sea-water diluted with distilled, 

 or in pure distilled water. In the latter case, the eggs became 

 "ghosts" of their former selves, since the pigment dissolved out 

 and increased osmotic pressure caused the egg to absorb water 

 and swell enormously. If an excess of iodine is added to normal 

 eggs, they also become pale, but due to a precipitation of the 

 pigment, which gathers as a small dark mass near one side of 

 the egg. There is seldom indication of swelling or ghost forma- 

 tion. 



The membranes obtained by the iodine method weie identical 

 with the true fertilization membranes which appear when the 

 sperm enters the egg. They do not resemble the membranes 

 formed by treatment with butyric acid and hypertonic sea-water, 

 which Loeb describes as very difficult to see, excepting by the 

 trained observer. This normal appearance of the membranes 

 was noted by others accustomed to distinguishing types of mem- 

 brane in Arbacia. The significance of the nature of this mem- 

 brane will be discussed in a later paper 



Reference to Table I. brings out a result that was wholly un- 

 expected. It is commonly supposed that eggs shed by the 

 animal are in better condition and more fertile than those taken 

 from the ovary. The results with one female, whose shed eggs 

 produced only 3 per cent, cleavages, while those shaken from the 

 same ovaries gave 94 per cent., were so striking that the averages 

 were computed. It was found that the shed eggs averaged 

 only 43 per cent, as against 80 per cent, cleavages from the 

 eggs shaken from the ovaries. It is planned to test this during 

 the height of the breeding season, so as to discover whether this 

 is a normal occurrence or whether the "shed" eggs are more 

 likely to be "over-ripe" than the others, late in the season. 



1 Loeb, Jacques, " Die chemische Entwicklungserregung, etc.," Julius Springer, 

 Berlin, 1909. 



2 McClendon, J. F., " On Artificial Parthenogenesis of the Sea-urchin Egg," 

 Science. 1909, Vol. 30, pp. 454-455. 



3 Glaser, O. C., " On Inducing Development in the Sea-urchin (Arbacia punc- 

 tulata), Together with Considerations on the Initiatory Effect of Fertilization," 

 Science, 1913, Vol. 38, pp. 446-450. 



