AUTO-PARTHENOGENESIS IN ARBACIA AND ASTERIAS. 403 



chiefly I believe because the evidence in support of it has been 

 unfortunate not only in a purely technical sense which has been 

 justly criticized, but also because it was gathered under a mis- 

 apprehension apparently as to exactly what R. S. Lillie had 

 suggested. So far as I can see, experiments in which the perme- 

 ability of fertilized eggs is compared with that of unfertilized 

 have no bearing on the question, for no such difference was 

 postulated, but only that the "increased permeability is ... 

 temporary in normal or in favorable parthenogenetic fertilization" 

 ('ii, p. 307). 



If this idea is correct we might expect two things to happen at 

 fertilization in the egg of Arbacia. Since this egg before im- 

 pregnation actively secretes materials that discolor the sea-water, 

 the discoloration produced by eggs undergoing fertilization might 

 be greater. I have found (*I4 2 ) that it is one and a half times 

 that of eggs not undergoing impregnation. Further, fertilized 

 eggs, after the process is complete, do not discolor the sea-water. 

 In the second place even a temporary increase in permeability 

 should result in a change in volume if the eggs remain in a medium 

 that remains constant during the period under discussion. 

 Measurements show ('I4 1 ) that the eggs of both Arbacia and 

 Asterias are smaller in volume after fertilization than before. 



I therefore consider the idea of increased permeability during 

 fertilization correct, and that we may suppose all cases of fer- 

 tilization, whether with sperm or without to have this one point 

 in common. Since many of the results now published had not 

 been found at the time I wrote my preliminary paper ('I3 1 ) I 

 threw emphasis on this common attribute in section VIII. This 

 emphasis I do not wish to withdraw as the result of later work, 

 for this has only strengthened my conviction that in fertilization 

 an increase in the permeability of the ovum actually occurs. 

 The only question at issue seems to me to be the significance of 

 this change for the initiation of development. 



On this particular point I also postulated the loss of substances 

 antagonistic to oxidation. This suggestion was based on the 

 fact that substances are lost during the act of fertilization at a 

 higher rate than before, and finally that the presence of egg- 

 secretion in certain concentrations retards development. The 



