224 



GENERAL EMBRYOLOGY 



Z> 



FIG. 106. Diagrams illustrating the distribution of the paternal and maternal 

 chromosomes during cleavage. A. Zygote containing sperm, d\ and egg, 2 , 

 pronuclei, with similar chromosome groups. B. First cleavage figure. All the 

 chromosomes on the spindle, and each divided. C. Two-cell stage, each nucleus 

 containing equivalent chromosome groups of paternal and maternal origin. 

 D. Second cleavage figure; the first figure is repeated in each cell. E. Four-cell 

 stage. Nuclei all alike, and each composed of similar contributions from each 

 parent. 



