Terrestrial And Sigman Metazoans

Stages of Terrestrial Evolution
protozoa, some swimming with cilia;

a clump of aggregated cells;

a hollow sphere;

two concentric spheres;

spheres with specialized inner and outer walls and an opening at either end for intake and excretion;

colonies like sponges and corals;

cells joined end to end as segmented worms;

complex organisms retaining bilateral symmetry and an oral-digestive-anal tract;

branched-off organs like heart and lungs adopting the canal principle.

Stages of Sigman Evolution
spheroidal, not flat, protozoans with universally spaced cilia for swimming and whipping food towards the animalcule which is permeable, without orifices;

cells joined by linking cilia which became tubes for support and fluid conveyance;

complex organisms comprising spheroids connected by rods with axial or radial, not bilateral, symmetry and permeable skin;

possibly sensing and thinking with the whole body, not needing a brain, thinking more slowly but also more deeply.

Conclusion
Human beings have a lot to learn from the disgusting looking alien.