1 88 Charles R. Stockard 



was repeated three times and each time it so happened that exactly 

 one-half of the embryos had only one eye. These cyclopean fish 

 were rather abnormally shaped though they were able to twist 

 about and wave their pectoral fins vigorously. The other embryos 

 were apparently normal in all particulars, the magnesium seeming 

 not to have affected them. 



In sections the one-eyed condition was found to result from the 

 union or fusion of the Anlagen of the two optic vesicles. Cases were 

 found illustrating various degrees in this fusion, it seemed as 

 though the optic vesicles were formed too far forward and ventral 

 and thus their antero-ventro-median surfaces fused. This condi- 

 tion results in one large optic vesicle which in all cases gives more 

 or less evidence of its fused or double nature. 



As a rule but a single lens is formed, the size of which depends 

 upon the size of the optic cup or more exactly upon the size of the 

 ectodermal area influenced by the optic cup to form a lens. This lens 

 formation is interesting in connection with the results of the experi- 

 mental work of Lewis ('04) and others on the lens development in 

 Amphibians. I ('07) have entered into a more detailed discussion 

 of this subject elsewhere. 



The lens was found to show a double or fused structure in one 

 case out of the ten embryos that were sectioned; the other portions 

 of this eye were also more distinctly double than was usually the 

 case. This condition represents the last step in the fusion of the 

 two eyes, shghtly greater fusion would result in a single eye. 



With no other solution has such a condition as the above been 

 procured, and its abundant occurrence in sea-water solutions of 

 MgCl2 strongly indicates that this one-eyed condition is character- 

 istic of the action of such solutions on the developing Fundulus 

 embryo. 



Solutions of MgClj TO m + NaCl ^ m in distilled water, and 

 MgClj i m + NaCl i m in sea-water were tried on the eggs with 

 the results following: 



The distilled water mixture produced no effect on the develop- 

 ment, nor do such strengths of the two salts employed separately. 



The sea-water mixture contained twice as much MgCU as the 

 distilled water one. The results are instructive. When eighteen 



