The Cleavage of the Egg of Lepidosiren 

 paradoxa. 



By 

 Agnes E. Miller, 3I.A., 



Department of Zoology, University of Glasgow. 



With 12 Text-figures. 



The process of cleavage in Lepidosiren was tirst described 

 by Professor Graham Kerr in his paper on the development 

 of the external features of this animal in the ' Philosophical 

 Transactions of the Eoyal Society ', B, vol. cxcii, 1900. Since 

 the date of Professor Kerr's expedition additional material has 

 become available from which it has been possible to make up 

 a more completely graduated series of segmentation stages. 

 The following paper deals with this material and may be 

 regarded as supplementing Professor Kerr's paper. In referring 

 to the various stages I use the same numbers as Professor 

 Kerr used in the paper already mentioned and also in his 

 ' Normentafel '.^ 



Stages 2-3 . — Professor Kerr's earliest cleavage stage (2) 

 showed the first meridional furrow bisecting the finer-grained 

 apical cap but not extending beyond its margin ; while in 

 the second stage figured by him (3) the first meridional furrow 

 had spread down to the equator of the egg, while the second 

 meridional furrow at right angles to the first extended to just 

 beyond the margin of the apical cap. 



Amongst the new material is an egg (Text-fig. 1) in which 

 the first meridional furrow has extended right to the abapical 



^ Keibel's ' Normentafeln zur Entwicklungsgeschichte der Wirbeltiere ', 

 Zehntes Heft, 1909. 



NO. 268 L 1 



