On the reaction of the pigment cells in normal and albinous frog larvæ

Abstract

In the experimentally produced albinous frog larvæ which follow a successful early extirpation of the epithelial portion of the hypophysis, a pigmentary system is produced which is not only strikingly different from the normal in its anatomical and physiological condition but also exhibits striking departures from the normal in its physiological responses.

Normal larvæ kept in diffuse light and on an indifferent background usually show a fully expanded, or only slightly contracted, condition of the epidermal melanophores¹ and a completely contracted, or but slightly expanded, condition of the corial xantholeucophores. This condition can almost always be somewhat exaggerated by submitting the larvæ to the simultaneous action of low temperature and darkness, when the epidermal pigment cells are fully expanded and the corial xantholeucophores minute, silvery dots. When such larvz, or those from an indifferent environment, are submitted to reverse conditions, i. e., the simultaneous action of warmth (33°-35° C.) and sunlight, these two classes of pigment cells react in the reverse way and in from one half to one hour exhibit a picture of contracted melanophores and widely expanded silver cells. It is thus seen that the reactions of the two groups of superficial pigment cells-the epidermal melanophores and the corial xantholeucophores-go hand in hand and are in a reverse direction.

Attention has already been called to the constant great expansbn of the corial xantholeucophores in the albinos, an expansion which exceeds considerably that which can ever be obtained by the action of sunlight and heat on normal larvz Moreever, it is difficult to influence by physiological means this great expansion of the xantholeucophores in the albino. On the other hand, the epidermal melanophores of the albinos, which exhibit various stages of contraction, are widely expanded by the action of heat and light, an effect just the opposite of that which the same factors produce in the normal skin.