Arti-jicially Produced Cyclopean Fish 319 



The occurrence of this lens recalls at once Herbst's ('01) argu- 

 ment regarding the independent origin of the lens. He held that 

 "if the lens really developed independently of the optic cup, then 

 in the case of median cyclopia the two lateral lenses should arise 

 in their usual positions; but they do not, and furthermore, the 

 Cyclopean cup gets a lens from ectoderm out of the usual lens- 

 forming region." The Fundulus embryos show lenses arising 

 at times in their usual places and often in other places, independ- 

 ently of the optic cup. We may suppose that in these embryos 

 certain areas of the ectoderm are at times out of their normal posi- 

 tions, and thus explain the promiscuous distribution of independ- 

 ent lenses. 



Finally, embryos exist in which no indication of the optic cup 

 can be found, these may be said to have passed beyond the ex- 

 treme Cyclopean condition. They are not ordinary individuals 

 that are merely blind, since the mouth is usually distorted and 

 sometimes the snout-like structure which accompanies cyclopia 

 is present. This suggests the possibility that the "proboscis- 

 mouth" is not entirely due to its normal position having been 

 usurped by the cyclopean eye. Some of these embryos have free 

 lenses and others no optic parts at all. Figs. 54 and 55 are two 

 transverse sections from the same embryo, the anterior one shows 

 a lens lying against the olfactory pit but free from all connection 

 v^ith the central nervous system. Fig. 55 shows a second lens 

 lying close against the brain tissue. This embryo has no indication 

 whatever of optic cups, and seemed eyeless in life. Other indi- 

 viduals when carefully examined in section had neither an optic 

 cup nor any lens-like structures. 



We have thus reviewed a series of forms beginning with the 

 usual two-eyed embryos and passing through all degrees of double 

 eyes to single cyclopean eyes, to extremely small cyclopean eyes, 

 to individuals finally with only lenses present and no optic cups 

 and others with neither lens nor cup. 



