Developmental Biology (A) Cleavage Figure 5.8 anning electron micrographs of the cleavage of a frog egg. (A) First cleavage,(B) cy between the animal and vegetal cells after arising from the third division (A'n Second cleavage (4 cells). (C)Fourth cleavage (16 cells), showing the size discrepa from Beams and Kessel, 1976, courtesy of the authors: B and C courtesy of L. Biedler)Developmental Biology