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. All 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 



