THE DEVELOPMENT OF THE SPIRACULAR CARTILAGES OF THE SPINY DOGFISH, ACANTHIAS VULGARIS (SQUALUS ACANTHIAS)

Abstract

In A. vulgaris there are 2 spiracular cartilages in the anterior spiracular wall. These cartilages were studied in a number of developmental stages, and it was concluded that they represented mandibular rays. This conclusion is based on the following facts: 1) Their relation to the mandibular arch is the same as that of branchial rays to the branchial arches. 2) They chondrify at a later period than this arch, as do the ordinary branchial rays with respect to their corresponding arches. 3) At a certain stage of their development they branch, thus resembling the branching hyal rays. 4) They have never been found in continuity with the palatoquadrate, and hence could not represent the separate otic process of this cartilage.