FIELDS AND GRADIENTS IN NORMAL ONTOGENY 347 



eye 



Cyclopic frog tadpole produced by treatment with AZ/y lithium chloride for 

 3 hours in the early gastrula stage. The single median eye is beneath the surface. 

 The mouth is rudimentary. (From Child, Physiological Foundations of Behavior, 

 New York, 1924, after Bellamy.) 



^ 



Cyclopia induced by depressant agencies in Fundulus. Above: left, normal 

 young fish; centre, partial cyclopia, and_^right, complete cyclopia, induced by 

 treatment with magnesium chloride in stages prior to eye-determination. Below, 

 side view of the completely cyclopic specimen, showing malformed and ventrally 

 situated mouth. The treatment leads to the non-formation of the most anterior 

 and median regions. (After Stockard. from Wells, Huxley and Wells, The Science 

 of Life, London, 1929.) 



