252 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
divide. Segmentation proceeded in both groups. Five hours 
after the butyric-acid treatment or sperm fertilization, respec- 
tively, the position was as follows: The eggs fertilized with 
sperm were all in the sixteen-cell stage. Only 10 per cent of 
those treated with butyric acid had divided, and they were in 
the eight- to sixteen-cell stage. The others had not divided 
and showed no change. But soon after a change overtook 
them. Small clear droplets formed irregularly at the surface 
of the eggs similar to those extruded from sea-urchin eggs during 
heat or alcohol cytolysis. Ali the eggs of Asterina which formed 
these drops disintegrated. Often only a part of the Asterina 
eggs showed this formation of drops. In this case, only those 
eggs disintegrated which exhibited this formation of drops on 
their surface. The eggs that showed no drop formation, and 
segmented normally (i.e., about 10 per cent of the eggs with 
butyric-acid membrane), developed into normal larvae just 
like the eggs fertilized with sperm, all of which produced normal 
larvae. 
These experiments are very interesting, since they show 
that a not inconsiderable percentage of the eggs of Asterina will 
not disintegrate after artificial membrane formation, but will 
develop. These eggs therefore behave as if they already con- 
tained the substance or structure which we assume is formed 
under the influence of the second treatment. We may perhaps 
be justified in stating that in Asterina only 90 per cent of the 
eggs disintegrate after artificial membrane formation, while 
10 per cent are able to develop. All the eggs of the sea- 
urchins (S. purpuratus and Arbacia) disintegrate after artificial 
membrane formation unless they undergo a second treatment. 
But some of the eggs of the sea-urchins at Naples seem to be 
able to develop after mere artificial membrane formation. 
2. Ralph Lillie in working on the eggs of a starfish of the 
Atlantic coast, Asterias forbesii, found that a short heating 
of the eggs to between 35° and 38° C. caused them to form a 
