Experimental studies on the columella-capsular interrelationship in the turtle Chelydra serpentina.

THE reciprocal effect of two neighbouring structures of different origins on each other during development is of considerable interest to the embryologist. Such a relationship exists between the columella auris and the auditory capsule in the vicinity of the fenestra ovalis. This particular relationship, in addition, embraces an aspect of fundamental importance to the morphologist viz. the possible derivation of part of the columella from the capsule. The vast literature pertaining to this latter aspect and particularly in regard to the development of the human stapes, was recently reviewed in great detail by Strickland, Hanson & Anson (1962). References to literature related to other vertebrates are found in e.g. van der Klaauw (1924), Versluys (1936), and Werner (1960). An earlier paper (Toerien, 1963) deals with the rather specialized problem of Amphibian stapes development The results of certain extirpation procsduivS on early embryos of the turtle {Chelydra serpentina) throw interesting h^ .. on the cclumella-capsule interrelationship. The planning of the operations was based on the following earlier observations: