Final answer:
The epithelium of phoronids is embedded with specialized cells such as nerve cells, contractile epithelial cells, enzyme-secreting cells, and nutrient-absorbing cells.
Step-by-step explanation:
The epithelium of phoronids is embedded with specialized cells such as nerve cells, contractile epithelial cells, enzyme-secreting cells, and nutrient-absorbing cells. These cells are found in the gastrodermis, which is the inner layer of the phoronid's body. The epithelial layers of phoronids are derived from the endoderm and ectoderm of the embryo.