AUTO-PARTHENOGENESIS IN ARBACIA AND ASTERIAS. 393 



10.50 Fertilization membranes 10.53 Fertilization membrane3 



indicated. indicated. 



12.15 P.M. Many eggs elongated. 

 2.00 Fertilization membranes. 2.00 P.M. Frequent cleavages. 



Frequent cleavages. 



9.00 A.M. Cytolysis. 9.00 A.M. Numerous dead blastulae. 



One free swimming bias- Much gastrulation. 



tula. 



In other tests similar results were obtained. Unfortunately 

 this work came at the end of the Asterias breeding season, and 

 further experiments were impossible. Those performed however 

 are sufficient to show that parthenogenesis can be induced in 

 Asterias as in Arbacia by the use of its own egg-secretion. Owing 

 to the existence of a perivitelline space within which the cleavage 

 products of the Asterias egg are held, it appears likely that better 

 results w r ill ultimately be achieved than in the auto-partheno- 

 genesis of Arbacia. In fact as indicated above, even without 

 hypertonic after-treatment, which in first experiments was always 

 omitted for the sake of control, one of my auto-parthenogenetic 

 Asterias cultures proceeded to the gastrula stage. 



" HETERO-PARTHENOGENESIS." 



" Hetero-parthenogenesis " as the sequel will show, is prooably 

 not the correct word, but I use it here as a convenient heading 

 for experiments in which development was initiated in Asterias 

 eggs by the use of Arbacia secretion. Such experiments sug- 

 gested themselves, as the result of the earlier observations on the 

 increase in the permeability of various types of cells. From 

 these one might anticipate " hetero-parthenogenesis, " a process 

 which was indeed successfully induced as the following experiment 

 indicates: 



10.35 A.M. i volume mature Asterias eggs, 

 i volume Arbacia secretion. 

 No immediately visible effect. 

 10.50 Fertilization membranes indicated. 



2.00 P.M. Numerous cleavages. 



THE FERTILIZIN THEORY. 



After I had discovered auto-parthenogenesis through the ob- 

 servation that the egg-extracts are permeability increasing agents, 

 I consulted with Professor F. R. Lillie who had been performing 



