Final answer:
Blood fluke embryos develop inside freshwater snails, which serve as an intermediate host for this parasite.
Step-by-step explanation:
Blood fluke embryos develop inside specific intermediate host organisms; these hosts are often certain species of freshwater snails. Blood flukes are a type of parasite that can cause the disease schistosomiasis in humans. The entire life cycle of blood flukes involves several developmental stages and at least two different hosts. The intermediate hosts, the freshwater snails, play a crucial role as the environment where the blood fluke embryos mature. Humans or other mammals serve as the definitive hosts where the flukes reach maturity and reproduce, continuing the cycle of infection.