64 PROBLEMS OF FERTILIZATION 



are prevented from meeting rapidly, e.g., by the use of 

 anaesthetics, as in E. B. Wilson's experiments (1901), 

 the sperm nucleus may grow to the size of the egg nucleus, 

 and, after recovery from the anaesthetic effect, the two 

 equal nuclei unite. 



We have, therefore, to consider two questions to 

 the extent that morphological observation admits: 

 (a) What determines the movements of the germ nuclei 

 within the egg and their union ? (b) What is the nature 

 of the union quantitatively and qualitatively ? 



a) As regards the first question, Roux, in 1883-87, 

 resolved the movements of the sperm nucleus w^ithin 

 the egg into two components, which he called the pene- 

 tration path and the copulation path. His observations 

 were made on the frog's egg, in which the spermatozoon 

 leaves behind it a trail of pigment, marking out its 

 path, which is usually curved or exhibits an angle. He 

 conceived the first part of the path to be a continua- 

 tion of the direction of penetration; the second part 

 of the path he conceived to be determined by an attrac- 

 tion between the egg nucleus and the sperm nucleus. 

 That there is an energy of penetration of the sper- 

 matozoon which persists in the same direction after 

 entrance into the egg is scarcely tenable, because 

 the penetration itself is not a result of the locomotor 

 energy of the spermatozoon; there is also no reason 

 to assume that the nuclei as such exert attraction on 

 one another. Such an assumption has no basis in 

 fact beyond the actual meeting of the germ nuclei, 

 which can equally well be explained on other more 

 reasonable and less mystical grounds. The view has 

 been presented that the movements of the sperm nucleus 



