264 CHARLES R. STOCKARD 



5. Both anterior lateral parts of the neural fold cut away just before 

 the folds close together 



The operation consisted in clipping away with scissors the 

 lateral wall of the neural groove from both sides; that is, the 

 raised folded parts and the dorsal portion of the lateral neural 

 wall indicated in figure 4. The actual crest of the neural folds 

 is of course not future lateral material as in the closure of the 

 furrow to form the neural tube the crest becomes dorsomedian 

 as just mentioned. 



Four embryos were successfully operated upon in the given 

 manner. Three days after the operation they were killed and 

 prepared for study. All of the embryos were found to possess 

 both eyes in well developed conditions. 



Five other embryos in a similar stage of development were 

 operated upon so as to remove the lateral neural folds as indi- 

 cated in figure 4. 



Four days after the operation the embryos were killed. Study- 

 ing these embryos in section showed that four of the five pos- 

 sessed both eyes in a well formed condition giving no indication 

 of the injury while the fifth individual possessed only one eye. 

 This last specimen was evidently cut too near the median line 

 on one side so that the future eye material of that side was 

 destroyed. 



Thus in nine specimens with both sides operated upon, eighteen 

 operations, only a single eye was missing. The other seventeen 

 operations did not cause smy noticeable effect in either the devel- 

 opment or nature of the resulting eye. 



These experiments clearly demonstrate that the eye anlage is 

 not located along the lateral edge or border of the medullary 

 plate or groove, as Spemann holds. The importance of such 

 facts in connection with opposing explanations of certain eye 

 abnormalities will be fully considered in a following section of 

 this paper. 



The next experiments to be presented were performed in order 

 further to substantiate the fact that the eye parts do occupy a 



