Adaptations and the Influence of Light on Animal Tissues

Abstract

PROF. MEEK, in his letter to NATURE of Oct. 5 on “Adaptation”, has used in illustration of his views instances of crustacean races (of the amphipod Gammarus duebeni and the copepod Canthocamptus pygmcæus) residing in pits and mines which had lost their colour and eyes without losing the power of reproducing those features on becoming once more acquainted with light. In Prof. Meek's opinion, more prolonged exposure to environmental strain might make this restoration more difficult by impairing the reversibility of the reaction, and he suggests that this sort of adaptation to life in the dark is ‘psychogenetic’ in origin. In addition to the many eyeless Crustacea of purely cavernous habit, Cyclops agilis Koch has been found underground with degenerate eyes, but the same and four other species of Cyclops as well as Canthocamptus staphylinus Jurine have often been found in the dark with normal eyes; loss of pigment has been observed in certain Ostracoda in similar situations (Moniez, Bull. biol. N. France, 1, P. 176; 1888).