Ii6 



PRINCIPLES OF EMBRYOLOGY 



FlGUKE 7.4 - 

 Isolation and grafting of blastomeres in ascidians. 

 {a) Separation of the 8-cell stage of an ascidian into four pairs of cells. The 

 two posterior animal cells give ectoderm, and the two posterior vegetative 

 ones mesoderm, including muscle, and endoderm; this corresponds with 

 their prospective fate. But the anterior animal ones give only ectoderm, with 



