an apparatus and process are disclosed for growing tubular crystalline bodies according to the edge defined , film - fed growth process , wherein the apparatus has at least one exterior passage and at least oen interior passage formed in its crucible die assembly and associated parts , whereby gases introduced into at least one exterior passage will be delivered to the zone located outside the growing crystalline body adjacent to the growth face on the die member , and gases introduced into at least one interior passage will be delivered to the zone located inside of the hollow crystalline body adjacent to the growth face on the die member , whereby the atmosphere in each of the zones may be separately controlled .