Abstract
The action of colchicine on development was studied by exposing early cleavage to optic cup stages of the fish, Oryzias latipes, to concs. of 1-1,000 to 1-100,000 for different lengths of time. Sensitivity of both the whole organism and its constituent parts decreases with age and differentiation. In addition to general retardative and inhibitory effects, types of developmental disturbance include variation in pigmentation of eye and body, cyclopia, modifications in size and shape of tail, irregularities in heart form and in the yolk-sac vessels; abnormal formation of blood, disturbance of body flexures and modifications of the brain. Apparently when gastrulation occurred, it was typical. Differential recovery was exhibited by certain tissues and organs. The effects are similar to those caused by X-rays and dinitrophenol.