Ultrastructural characteristics associated with the anchoring of corneal epithelium in several classes of vertebrates.

The electron microscopic examination of the basal cells of corneal epithelium certain species of Mammalia, Avia, Reptilia, Amphibia and Pisces was directed particularly towards the hemidesmosomes. Sections cut normal to the basal lamina and sections cut parallel to it were studied in order to establish the number, shape and distribution of the hemidesmosomes. Four basic types of hemidesmosome distribution were recognised among a limited representation of the classes studied. (1) Linear chains of hemidesmosomes (Mammalia, Rana, Bufo). (2) Rosette arrangement of hemidesmosomes surrounding pockets of basal plasma membrane (Avia, Anolis, Xenopus). (3) Punctate hemidesmosomes with no arrangement (Thamnophis). (4) Absence of hemidesmosomes (Carassius). All animals showed a basal lamina, basal pinocytotic vesicles, anchoring filaments, tonofilaments, and interdigitating foot-processes. It is suggested that anchoring filaments deserve to be studied more thoroughly in certain other types of epithelia which do not have focal hemidesmosomes, but require firm anchorage to a basal lamina.