Stockard, The Experimental Production of various Eye Abnormalities etc. 639 



often occur among the fish embryos with which I have experi- 

 mented. 



The cyclopean fish embryos are in all respects exactly com- 

 parable to the human cyclops. One eye exists in the middle of 

 the face and the nasal pits are often represented by a single or 

 double pit in front of the eye. The eye conditions show all steps 

 in a series beginning with two eyes unusually close together, two 

 approximated eyes, a double eye with two lenses, two pupils, etc., 

 a laterally broad eye with a double retinal arrangement and a 

 single lens and pupil, and a typically single eye showing no indi- 

 cations of its double nature. The later condition may be termed 

 typical or perfect cyclopia, from this we pass to extreme cyclo- 

 pean eyes which are unusually small, sometimes deeply buried 

 in the head, others with small optic cups and illfitting lenses 

 which protrude beyond the eye, and, finally, all retinal or optic 

 cup portions of the eye may be absent, with independent lenses 

 present, or both optic cup and lens may fail to form and eyeless 

 creatures result. Many illustrations of all these stages have been 

 found and studied among the hundreds of cyclopean fish which 

 have been produced by these methods. 



Some of the embryos present perfectly normal bilateral brains 

 and show no abnormality other than the cyclopean eye and cha- 

 racteristic proboscis-like mouth. The cyclopean eye occupies an 

 antero-ventral position, and many fish with such an eye hatch from 

 the egg and swim about for a month or more in a perfectly nor- 

 mal fashion, the cyclopean eye functioning as an efficient organ 

 of sight. 



The development of the cyclopean eye in human monsters 

 has been difficult to interpret on account of the scarcity of ma- 

 terial and want of early stages of the defect. Such abnormalities 

 are not readily explained from later stages. In the summer of 

 1906, when these monstrous fish were first produced, I secured 

 only later stages and on finding all degrees of union between 

 the eyes concluded that the cyclopean condition resulted from 

 a more or less intimate fusion of the two eye components after 

 they had arisen the brain. This position has been held by other 

 workers both before and since my study. A more careful investi- 

 gation, however, of the earliest stages of cyclopia in the living 

 eggs and in sections shows that the final condition of the eye 

 is foreshadowed in the first appearance of the optic anläge from 

 the brain. The early eye is either perfectly single or double from 

 the start, and the union of the two components does not become 

 more intimate during development, even though the eye may 

 develop partially within the brain itself. 



In addition to the above series showing the various degrees 

 of cyclopia, another series of opthalmic defects were induced by 

 the same chemical substances. These individuals have one per- 



