SECRETION AND STABILIZATION OF THE LAYERS OF THE EGG CAPSULE OF THE DOGFISH SCYLIORHINUS-CANICULA

The egg capsule of the dogfish is a unique, collagenous, layered structure secreted by the nidamental gland which has nine, remarkably discrete, transverse zones of tubular glands. The present paper traces the origin of the four layers of the capsule to particular zones within the gland. Evidence is presented for the existence of DOPA, DOPA oxidase, protein(s) rich in tyrosyl residues and a peroxidase within the same storage granules within the secretory cells of the C and E zones. It is suggested that these interact when secreted to cross-link the inner and outer surfaces of the egg capsule. Evidence is presented that the middle layer which forms the bulk of the thickness of the egg capsule and has the highest collagen content may be partly stabilized by the peroxidation of tyrosyl residues. The mechanical significance of cross-linking in this system and the possible cytological mechanisms involved in the secretion of the tanning agents and enzymes are discussed.