436 J, GRAY 



facts of nonucil and hybrid fertilization. Tho theory of fertiUza- 

 tion put forward by F. R. LilHe does not appear to be apphcable 

 to the facts of artificial parthenogenesis. 



2. The facts of normal fertilization appear to indicate that 

 the action of the spermatozoon on the egg is essentially of 

 a physical nature. 



3. Evidence is advanced in favour of the view that the activa- 

 tion of an unfertilized egg by a spermatozoon is due to the 

 electro-motive force set up when the two gametes come into 

 contact. The inert egg is activated by the spermatozoon in the 

 same way as any other resting cell is activated when in intimate 

 contact with an active neighbour. 



4. After activation normal development only occurs if two 

 asters are present in the egg. Under normal circumstances the 

 second aster arises in the egg in conjunction with the male 

 pro-nucleus ; in artificially activated eggs the second aster arises 

 when the egg is treated with hypertonic solutions. 



5. In the case of the echinoderm egg the formation of the 

 fertilization membrane is discussed. One essential step in the 

 activation of these eggs is the removal of a continuous lipoid 

 lilm from the surface of the unfertilized egg. 



6. The view is expressed that the only essential effect of egg- 

 secretions on spermatozoa is the capacity of these substances, 

 in certain cases, of increasing the activity of the male gametes. 



References. 



1. Bredig und Weinmayr. — ' Zeit. f. Physik. Chem.', vol. 42, p. 602, 1903. 



' Biochem. Zeit.', vol. 6, p. 283, 1907. 



2. Buchanan, R. E. — ' Journ. of Bacteriology ', vol. 4, p. 73, 1919. 



3. Cohn, E. J.—' Biol. Bulletin ', vol. 34, p. 167, 1918. 



4. Darling, C. R. — ' Liquid Drops and Globules ', London, 1914. 



5. Doncaster, L.— ' Phil. Trans. Roj'. 8oc.', vol. 196 B, 1903. 



6. ElUs, R.— ' Zeit. f. Physik. Chem.', vol. 78, p. 321, 1911 ; vol. 80, 



p. 597, 1912. 



7. Glaser, O.— ' Science ', vol. 38, p. 446, 1913. 



8. Gray, J.—' PhU. Trans. Roy. Soc.', vol. 207 B, p. 481, 1916. 

 9. ' Proc. Roy. Soc.', vol. 91 B, p. 147, 1920. 



10 Ibid., vol. 93 b, p. 122, 1922. 



