1. Ectoderm: The outermost layer, which gives rise to the skin, nervous system, and sensory organs.

2. Mesoderm: The middle layer, which develops into muscles, bones, circulatory system, and excretory system.

3. Endoderm: The innermost layer, which forms the lining of the digestive tract and associated organs.

It's important to note that these layers are not just present during embryonic development but continue to contribute to the formation of different tissues and organs throughout the life of the worm.