CLEAVAGE OF LEPIDOSIUEN 505 



( y 2 and 5f 8) are seen to be tlisplaced in each case so that their 

 outer ends reach one of the meridional furrows, and in the case 

 of one of them the furrow has become practically latitudinal. 

 Owing to the increasing frequency of such displacements 

 combined with increasing ' loss of step ' of the various blasto- 

 meres in their successive fissions, the regularity of the segment- 

 ing process becomes from now onwards completely obscured. 

 In conclusion I desire to thank Professor Graham Kerr 

 both for providing me with the material on which these notes 

 are based, and also for his kind supervision during the course 

 of the work. I should like further to thank the Carnegie Trust 

 for providing the illustrations to this paper, and Mr. A. Kirk- 

 patrick Maxwell for the care and skill with which he has carried 

 them out. 



