HISTOLYSIS AND REGENERATION OF ANURAN TAIL SKIN

¹ DEPARTMENT OF BIOLOGY, UNIVERSITY COLLEGE, NEW YORK UNIVERSITY

1. Uniform-sized tail-skin grafts were secured from extreme dorsal, ventral, and one intermediate region of the tail and transplanted, autoplastically, to the backs of non-metamorphosing Rana catesbiana tadpoles. Artificial metamorphosis was then induced and the histolysis or reduction of the grafts studied. The median-source graft was invariably the first to undergo reduction followed in order by the ventral and dorsal, regardless of their antero-posterior transplantation sequence on the back.

2. Similar grafts of tail-skin were transplanted, autoplastically, to the backs of non-metamorphosing larvæ, and artificial metamorphosis subsequently induced. At arbitrary stages of reduction the grafts were retransplanted, homoioplastically, to the backs of non-metamorphosing laræ and allowed to regenerate. The median graft was the first to complete regeneration, as determined by histological reconstitution; the ventral being the second and the dorsal third.

3. The histolysis and regeneration of tail-skin always involves an orderly sequence of cellular changes. For both of these processes the sequence was determined as epidermis-dermis-subcutis.

4. It is concluded that the histolytic sequence is due largely to a time differential in the onset of histolysis. The regenerative sequence is probably the result of a time differential in regenerative incipience.

5. The physiological basis of these sequences is inherent in the tissues, and it is inferred that they may be determined or conditioned by different metabolic rates typical of each particular level.