Mouse Anatomical Dictionary - Stage 1 (One cell egg)

TS1:    
|   TS1: first polar body [1] 
|   TS1: one-cell stage [2] (fertilized egg,1-cell stage,1-cell embryo)
|   TS1: polar body  
|   TS1: second polar body [3] 
|   TS1: zona pellucida [4]