Complex sentence: The pouch serves as an incubator for a larval Goa'uld, known as a "prim'tah", which improves their ability to successfully take a host upon maturation from 50% to nearly 100%.
Split into simpler sentences: The pouch serves as an incubator for a larval Goa'uld. Implanted during a "coming of age" rite known as a "prim'tah", the pouch improves the Goa'uld's ability to successfully take a host upon maturation from 50% to nearly 100%.