170 A. H. REOTNAT-D BULLER. 



tact with its outer surface, and also in tlieir becoming 

 attached to the living egg. 



6. The vast number of eggs, and still vaster number of 

 spermatozoa produced, together with the motility of the 

 latter and the action of sea-currents, quite suffices to bring 

 the male sexual cells into contact with the zona pellucida. 



7. Many writers have supposed that chemotaxis is a 

 constant factor in the fertilisation of animal eggs. This 

 generalisation, which has been made by arguing from the 

 attraction of the spermatozoa to the eggs of certain plants, 

 is as yet entirely without experimental justification. From 

 my own results with the Echinoidea, which are in accordance 

 with those obtained by Massart in the case of the frog, and 

 with the work of Dewitz upon the fertilisation of the eggs of 

 certain insects, I have been led to suppose that chemotaxis, 

 at least for a great number of animal species, plays no 

 role whatever in bringing the sexual elements together. 



The work for the above paper was done at the Stazione 

 Zoologica, Naples, during the months of Mai'ch and April of 

 each of the years 1900 and 1901. It gives me much pleasure 

 to thank the Committee of the British Association for grant- 

 ing me the use of the table, and also to acknowledge my 

 indebtedness to the staff of the Stazione Zoologica for 

 supplying me with material and apparatus during the 

 research. 



