256 CHARLES R. STOCKARD 



optic anlagen originally located in the medullary plate or tube? 

 The present communication will present the results of experi- 

 ments aimed towards an answer to this question. Certain inter- 

 pretations put forward by Spemann regarding the origin and 

 development of the primary components of the eye will also be 

 considered. 



MATERIAL AND METHOD 



The material used in all the experiments has been the develop- 

 ing embryos of the salamander, Amblystoma punctatum. Am- 

 blystoma eggs are surrounded by masses of jelly-like material 

 from which they may readily be separated. The eggs live per- 

 fectly without the jelly mass, provided they are well covered 

 with fresh water. 



These eggs are of sufficient size to render it possible to cut 

 out with fair accuracy definite regions or groups of cells from the 

 medullary plate or groove. 



The method of experiment has been entirely by mechanical 

 operation. This method is particularly useful for the problem 

 in hand since definite areas may be removed and the results 

 studied. The operations were made under a binocular micro- 

 scope. Fine steel needles and the smallest scissors were used as 

 instruments. 



The embryos were kept from three to five days after the oper- 

 ation in water which had been previously boiled. They were 

 killed in a mixture of one part formalin to three parts saturated 

 corrosive sublimate, left for three hours, rinsed in water and 

 put into 70 per cent alcohol with iodine. Others were fixed for 

 three hours in Bouin's fluid, formalin and picroacetic. The sec- 

 tional embryos were stained with Delafield's hematoxylin and 

 eosin. 



