Artfficially Produced Cyclopean Fish 311 



Fig. 38 is a section through a unique double eye; no other such 

 case was found. The two retinal components are connected 

 along their median dorsal line within the brain and extend down 

 facing one another. They are like the two sides of a leguminous 

 pod; between the two a single lens is placed suggesting the seed 

 in the pod. Enclosing the ventral part of the retinal components 

 is a choroid coat shown in heavy black. This choroidal coat does 

 not fully encompass the retinal areas, a part of which extends 

 dorsally far up into the brain. The anterior end of the eye is 

 V-shaped in section. The optic cup anlagen in this case must have 

 been closely united from their first origin in the brain, since por- 

 tions of the retinal region are still contained within the brain 

 itself, yet during development they did not fuse into a single eye. 

 A single nasal pit is present and the mouth is ventral and pro- 

 boscis-like. 



An almost single eye is indicated in section, Fig. 39. The 

 choroid coat surrounds the retina, the latter showing slight traces 

 of its compound nature. Two lightly staining regions of nerve 

 tissue are seen and the entire eye is unusually wide laterally. 

 The single lens is normal. The brain here is also normal and 

 the eye occupies a ventro-median position. A further union of 

 the eyes gives the 



c Perfect Single Cyclopean Eye and Normal Brain 



The Cyclopean eyes are in many cases perfectly single, resem- 

 bling in all respects, except their position, one eye of a normal pair. 

 They are placed immediately ventral and their antero-posterior 

 mid-plane is in the median line of the embryo. The brain in 

 such a Cyclops is often normal in all general respects. Figs. 40 

 and 41 represent horizontal sections through the brain regions of 

 such a Cyclopean fish when seventy-seven hours old. Fig. 40, 

 the more dorsal section, passes through the mid-brain and shows 

 the two lateral, hemisphere-like bodies (corpora bigemina) with 

 well formed cavities. Behind these the section cuts the floor of 

 the hind-brain for some distance and finally crosses it where 

 the head bends. Passing ventrally through a number of sections, 

 we find the one shown in Fig. 41. Here only a small ventral 



