AUTO-PARTHENOGENESIS IN ARBACIA AND ASTERIAS. 395 



F. R. Lillie has also offered an interpretation of my results on 

 auto-parthenogenesis. He suggests that in the initiation of 

 development by employment of the egg-secretion, essentially 

 the same chemical chain is involved as in normal fertilization 

 except that the sperm, and naturally the sperm-fertilizin reaction 

 also, is dropped. In other words, in auto-parthenogenesis, the 

 egg-receptors are thought of as combining with the ovophile 

 side-chains of fertilizin which has not been bound to sperm- 

 receptors through its spermophile groups. 



Off-hand this supposition does not appear unreasonable. The 

 fertilizin is certainly present in abnormally high concentration in 

 the secretion as used for auto-parthenogenetic initiation, and the 

 mere fact that the secretion is a permeability-increasing agent 

 does not preclude the possibility that one of its constituents may 

 play an additional role in the initiation of development. If this 

 is true, it should be possible to block auto-parthenogenesis in 

 accordance with the scheme outlined above, although the absence 

 of the sperm and the sperm-fertilizin reaction restricts the op- 

 portunities to i, the loss of fertilizin; 3, the occupancy of the 

 egg-receptors; and 4, the occupancy of the ovophile side-chain of 

 the fertilizin. 



METHODS OF PREVENTING AUTO-PARTHENOGENESIS. 

 i. The Prevention of Auto-parthenogenesis by Washing the Eggs. 

 Several preliminary experiments in which the eggs before being 

 exposed to the action of the secretion were washed from 20 

 minutes to half an hour in great excesses of sea-water, proved 

 conclusively that this procedure very materially reduces the 

 number of cleavages, and the number of larvae, afterwards found 

 in the cultures. These results led to a more careful test carried 

 out on eggs which had been washed in excesses of sea-water for 

 24 hours. The sea-w r ater was changed frequently but at irreg- 

 ular intervals. These eggs were then treated in the usual way 

 with the secretion, but not a single cleavage was found. Thus 

 the effect of even slight washing is noticeable whereas prolonged 

 washing effectually prevents the auto-parthenogenetic cleavage. 

 From this we might conclude that something essential for the 

 initiation of development had been removed from the eggs. 



