402 



Prof. E. W. MacBride. 



[Nov. 7, 



spermatozoa into the sea-water about the same time. One cannot help 

 wondering whether some of Vernon's results may not have been due to the 

 neglect of the precaution of sterilising the sea-water. 



When the eggs of Echinus esculentus which have been fertilised with the 

 sperm of Echinocardium eordatum in sterilised sea- water are examined 

 under the microscope, many of them are seen to exhibit the fertilisation 

 membrane, showing that the spermatozoa have entered them. Their 

 cytoplasm is seen, however, to be undergoing the form of degeneration 

 known as cytolysis, that is, it is breaking up into globules. One of these eggs 

 is represented in text-fig. 4. Now Loeb (8) has produced the formation of 

 the fertilisation membrane and of the initial stages of development in 

 unfertilised eggs, by treating them'with butyric acid ; unless, however, they 

 were subsequently treated with hypertonic sea-water, cytolysis set in. He 

 consequently assumes that the spermatozoon has two actions on the egg : it 

 starts cytolysis, to which the formation of the membrane is due, and it also 

 checks the cytolysis which it has started. The spermatozoa of Echinocardium 

 act on the eggs of Echinus like butyric acid without the addition of hypertonic 

 salt solution. 



Fig. 4. — Au Egg of Echinus esculentus, which has been fertilised with the Sperm of 

 Echinocardium eordatum. 

 /., fertilisation membrane. 



Loeb (7, 8), Godlewski (3) and Kupelwieser (6) have been able to cause 

 the eggs of sea-urchins to develop, by adding to them the sperm of animals 

 belonging to quite different classes, such as Starfish, Crinoids, and Mollusca, 

 when the alkalinity of the sea- water in which the experiments were made 

 was artificially increased, and in all cases the resulting larvae exhibited 

 purely maternal characters. In endeavouring to apply this method to the 

 fertilisation of the eggs of Echinus with the sperm of Echinocardium 

 I made mixtures of 100 c.c. of sterilised sea-water with 1 c.c, 1-|- c.c, 2 c.c, 

 and 2| c.c. respectively of an N/10 solution of NaOH in distilled water, and 

 in these mixtures the cross-fertilisation was attempted. In the culture 

 which was made with a mixture of 100 c.c. of sea- water and 2 c.c. of N/10 

 solution of NaOH a few unhealthy granular blastulas were found, but none 

 developed into larvse. 



