[Experiments on the development of the pattern of organs in the anterior brain region in amphibians].

Defects produced by operations within the material underlying the prosencephalic area of the medullary plate do not cause corresponding localized missing of parts in the pattern of anlagen of the anterior brain. They only result in: 1. diminution of the induced organs and 2. cyclopic fusion of paired anlagen, as known following a general premature termination of the induction process. Defects in the lateral parts of the anterior archenteron roof produce diminution of the overlying areas of organs. Moreover, removal of the median stripe results in cyclopic fusion of the paired rudiments of the prosencephalic region including the eyes. A simultaneous separation of the two halves of the medullary plate prevents the fusion, with the consequence, that in spite of the missing of the median stripe a normal bilateral development takes place.Isolation experiments in the area of the eye rudiment of the neurula demonstrate, that, at least in the middle neurula stage, these rudiments exist in pairs, and that cyclopia must be due to a secundary fusion of the rudiments of the two sides. This means, that in the middle neurula the anlagen posess a certain mobility, even beyond existing cell borders.