This document describes and compares protostomes and deuterostomes. Protostomes are animals where the blastopore becomes the mouth, and have spiral cleavage, mesoderm from the 4d cell, and a trochophore larva. Deuterostomes are animals where the blastopore becomes the anus, and have radial cleavage, mesoderm from pouches off the gut, and a dipleurula larva. Sexual reproduction in protozoans involves fusion of gametes through syngamy or amphimixis, and can include conjugation during unfavorable conditions.