1 62 



Scientific Proceedings (54). 



in the interior of degenerating cells which have taken up the indi- 

 cator. The violet change is not due to free carbon dioxide, for 

 bubbling the gas through unclotted plasma containing congo red 

 fails to bring about an alteration in color. 



The observations show that tissue cells can withstand much 

 more considerable changes in the reaction of the medium round 

 about than has been supposed; and that their growth in vitro 

 may be very active in an acid medium. 



101 (797) 



The location of the optic anlage in Amblystoma and the interpreta- 

 tion of certain eye defects. 



By Charles R. Stockard. 



[From the Department of Anatomy, Cornell Medical College, New 



York City.] 



The early embryos of Amblystoma were operated upon so as 

 to remove definite areas from the open medullary plate in order 

 to determine the position of the materials which would give origin 

 to the future eyes. 



Preliminary experiments of sticking and disturbing the cells 

 in the anterior end of the medullary plate without actually remov- 

 ing these cells did not prevent the subsequent development of the 

 optic vesicles in an apparently normal manner. Cutting out 

 rectangular pieces of the anterior part of the medullary plate, 

 reversing the pieces and transplanting them merely caused the 

 eyes to develop in misplaced positions. These two experiments 

 demonstrate the fact that unless the future eye material is well 

 removed by the operation the optic vesicles may form. This 

 fact is important in considering the results of the following experi- 

 ments. 



A general statement of the results of the experiments may be 

 expressed as follows : Thirty embryos studied after various opera- 

 tions in which lateral portions of the medullary plate were removed 

 at slightly different developmental stages showed in twenty-four 

 individuals, or eighty per cent, of the cases, subsequent develop- 

 ment of both eyes, while only six specimens, or twenty per cent. 



