Who observed that embroys never pass through adult stages of their ancestors

Who proposed for the first time that developing animal embryo passes through stages resembling adults of its ancestors.

During embryonic period, animals repeat embryonic stages of their ancestors. This law is called :

The phenomenon observed when a beam of light is passed through a colloidal solution is

Bouquet stage is observed in :-

What is especially observed when a beam of light is passed through a colloidal solution?