Artifirially Produced Cyclopean Fish 335 



eye in a median position, the single cyclopean eye, an extremely 

 small anterior eye, a deeply buried ill-formed cyclopean eye, and 

 finally an entire absence of the eye. The embryos exhibit these 

 various degrees of the cyclopean defect from the earliest appear- 

 ance of the optic outpushings, and in no case was cyclopia due to 

 a union or fusion of the two eye components after they had 

 originated distinctly. 



5 A second type of monster designated as Monstrum monoph- 

 thalmicum asymmetricum, the monster with one asymmetrical 

 eye, was also common in the magnesium solutions. These indi- 

 viduals have one perfect eye of the normal pair but the other is 

 either. small, poorly represented or entirely absent. This condi- 

 tion is also present from the first appearance of eye structures and 

 is not due to degeneration or arrest of development. 



6 Both types of monsters often form lenses independently 

 of the optic cup stimulus. These self-originating lenses are also 

 capable of perfect self-differentiation, forming lens fibers and 

 appearing as transparent crystalline bodies. Such facts oppose 

 the idea that the lens during its origin and development is in a 

 dependent relationship with the optic cup, and show this view not 

 to be of universal application. 



7 The experiments conclusively prove that eggs may be in- 

 duced to develop into cyclopean monsters by external influences. 

 These influences do not mechanically injure or destroy certain 

 eye regions as does cutting or pricking. It follows, therefore, that 

 cyclopean monsters appearing in nature are not necessarily due to 

 germinal variations, but are far more likely the result of some 

 unusual external influence during development. 



8 The occurrence of the various eye monstrosities shown by 

 embryos which develop in magnesium solutions are all probably 

 due to a common cause and I suggest the following hypothetically: 

 Magnesium which possesses a decidedlv anaesthetic effect on most 

 animals and is inhibitory in its influences on muscular activity 

 may retard through degrees of anaesthesia the optic outpushings 

 in Fundulus embryos and thus account for the total absence of 

 eyes, small eyes, eyes which failed to develop energy necessary for 

 their normal separation and the other unusual conditions which 



