28 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the vertical fibres, and before the transverse walls are 

 complete vertical walls are initiated within the fibres, 

 commencing on both sides of the transverse wall, 

 gradually extending until the lower tier of nuclei are 

 enclosed in four separate cells, and the upper tier are 

 enclosed in four deep pockets, open to the cytoplasm 

 above. Simultaneous division now takes place in the 

 upper tier of free nuclei, and transverse and vertical 

 walls are again formed ; there are now two enclosed tiers 

 and one open tier. The next and last division that occurs 

 within the egg takes place in the lower tier. The 

 preceding appears to be the normal course of development 

 of the four pro-embrvos within the egg. 



This sequence of division, however, occasionally 

 varies ; instead of the second division taking place in the 

 upper tier of nuclei, it sometimes occurs in the lower ; and 

 the third division may take place in the upper tier instead 

 of the lower ; I have excellent examples illustrating 

 both varieties. What effect these apparent^ abnormal 

 divisions have upon the further development can only be 

 conjectured. Even though development continue, it is 

 highly probable that it will be limited, and not result in 

 the production of an embryo. I have many preparations 

 in which this group of cells is disintegrating, and others 

 with distinct abnormal development, one, for instance, in 

 which the upper tier have grown into the egg as elongated 

 cells, apparently suspensors ! 



While these five divisions have been proceeding other 

 great changes have been taking place within the egg ; its 

 cytoplasm has been constantly renewed by the outpourings 

 of the jacket cells, and as constantly used by the dividing 

 cells, until when the sixteen cells are fully developed, the 

 jacket cells are practically empty, and the egg cytoplasm 

 is nearly all used up. 



