asal Capsules From fishes to tetrapods, the nasal cap have had a complex history. The nasal capsules hol the olfactory epitheliur he form of a paired nasal sac(figure 7.27a). In actinop the nasal sac typically not open directly it rior(incurrent) and post the mouth. Instead, its ante current) narial openings establish lay across the for or a rout tory epithelium, del ring to it fresh chemical odors. By contrast each na of tetrapods opens directly into he mouth via an interna aris, or choana(figure 7.27b) Each na Way of an external naris establishing a respiratory route for airfn In additton to internal and ex ing within the