The photo below shows an early frog embryo after three mitotic divisions of a fertilized egg. this embryo has how many cells?

This embryo has 8 cells.

Explanation:

Just after fertilisation the embryo under goes cleavage.In frog, the first division takes place at the vegetal pole .Before the first division completes the second division begins at the animal pole, at right angles to the first division.At this stage the embryo has four cells.The third division occur at the equitorial plane, but slightly towards the animal pole.this third division divides the embryo into two regions: a ) rapidly dividing dividing region of micromeres  b) slowly dividing region of macromeres.after third division there are 4 micromeres towards the animal pole and 4 macromeres at the vegetal pole.

Mg is used to measure mass