Errect oF ARTIFICIAL MEMBRANE FORMATION 77 
It is of interest to add that fertilized eggs can also be caused 
to show this process of droplet formation during the first seg- - 
mentation, namely if they are caused to segment in an abnormal 
solution. It depends upon the degree of abnormality whether 
or not such eggs can afterward develop into normal larvae. 
When unfertilized eggs of S. purpuratus were exposed for about 
two hours to a hypertonic solution and fertilized with sperm 
immediately after they were taken out of the solution they were 
able to develop, but the first segmentation occurred often with 
droplet formation in the plane of division. When they were 
fertilized after they had been in the normal sea-water for some 
time they segmented normally. 
While the artificial membrane is enough to initiate the act 
of development, something is abnormal in the egg in so far as the 
process of cell division leads to its destruction. We should 
therefore expect that if we inhibit the process of cell division, 
the eggs would not perish. This conclusion is correct. 
It has been mentioned that cell division can be prevented 
in the fertilized sea-urchin egg by depriving it of oxygen or 
stopping oxidation by certain poisons, such as KCN. We will 
now proceed to show that if we deprive the sea-urchin egg of 
oxygen after artificial membrane formation, or put it in sea- 
water with a little KCN or chloral hydrate, we then inhibit the 
disintegration described above." Membrane formation was pro- 
duced in the eggs of a sea-urchin by treating them with butyric 
acid. The eggs were then divided into three portions. One 
remained exposed to the air, a second was placed in a flask 
through which was passed a stream of pure oxygen, the third 
in a flask of sea-water out of which practically all air had been 
driven by a stream of hydrogen, and in which the current of 
hydrogen passed through the vessel during the whole of the 
experiment. The eggs which had been exposed to oxygen in 
1Loeb, Untersuchungen ueber kinstliche Parthenogenese, D- 483; Biocheme 
Zeitschr., I, 192, 1906. 
