By changing the controlled variable.
The slide of stages in starfish development illustrates stages from unfertilized egg to gastrula—typical of echinoderms and chordates that have very little yolk in the egg. Three embryonic cell layers—ectoderm, endoderm, and mesoderm—are established. All adult tissues are derived from these layers.
criminal sad because Grandma Sammy is the best in the world because you can say, some can a movie about it and but it can be good and I don't know
