EGG OF ALLOLOBOPHORA FOETID A. 57 



tion sphere. You remember that in the ^^^ of Allolobophora 

 foetida (and this is true of a great many forms) there is no 

 sperm attraction sphere until the middle-piece enters the ^g^. 

 Thus the spermatozoon's having no middle-piece is in entire 

 accord with the fact that after it has entered the &gg we find 

 no sperm attraction sphere. 



It seems to me that we must study the centrosome under 

 the microscope to arrive at even approximately definite ideas 

 regarding these puzzling questions. We need our own obser- 

 vation to guide us through the labyrinth of conflicting views. 

 If one studies the attraction sphere through the literature alone, 

 the different theories and the shades of disagreement between 

 the numerous authors make any definite conception of the sub- 

 ject very difficult. I should suggest a sort of centrosome creed, 

 and then you can change it every time you read a new paper 

 on the subject. If you do not read too fast, you will perhaps 

 not have to change it oftener than forty times a year. 



My creed just now — just now, remember, this minute — is 

 something like this: 



I believe in the centrosome. 



I believe in tzvo centrosomes, the egg centrosome and the 

 sperm centrosome. 



I believe that the centrosomes of botJi sperm and egg are 

 cytoplasmic elements — and so on. 



I could make a very long creed; but the final article must be: 



I believe I really know very little about the subject, and 

 when I have read more I shall probably know less. 



