Artificially Produced Cyclopean Fish 315 



Fig. 45. This lens, although only nine micromillimeters in 

 diameter, has differentiated and shows perfect lens fibers arranged 

 in the usual concentric fashion. It has no connection whatever 

 with the eye, nor with any part of the central nervous system. 

 The small lens doubtless originated and differentiated its tissue 

 in an independent manner. The independent origin and self- 

 differentiation of lenses will be clearly shown in a following sec- 

 tion of this paper. Fig. 45 also illustrates the two lateral nasal 

 plates in section. 



The Cyclopean eye is thus seen to be at times single in nature, 

 showing no trace of a double composition. This may be con- 

 sidered the climax or perfection of cyclopia, if such an expression 

 is permissible. Eyes not completely united, or double-eyes, are 

 the incomplete or imperfect cyclopean condition, while the single 

 condition reduced or distorted may be termed extreme cyclopia. 



d Extreme Cyclopia: From the Abnormally Small Anterior 

 Cyclopean Eye to Entire Absence of Eyes 



Many cases are found representing the condition of extreme 

 cyclopia. They may be considered in order, beginning with the 

 least modified. In discussing the living embryo mention was 

 made of those with a small cyclopean eye placed far forward (Fig. 

 18). Sections of such eyes show them to be of a more or less 

 imperfect nature and sometimes deeply buried in the tissues of 

 the head. Fig. 46 shows a section through the small eye of a 

 hatched embryo eighteen days after fertilization. This eye is 

 placed in the extreme anterior tip of the head and the section 

 shows on the right side pigment spots which lie on the front end 

 of the forehead. The eye is unusually small and the living 

 embryo was abnormal, being unable to swim directly forward. 

 The nasal pits are united in the anterior eye region and a pro- 

 boscis-like mouth is situated ventrally. 



Two still more abnormal cyclopean eyes are shown in trans- 

 verse section by Figs. 47 and 48, both from thirteen day embryos. 

 In Fig. 47 the eye is close to the single olfactory pit, the retina is 

 differentiated into layers, but the lens is larger than the optic cup 

 so that it cannot fit completely into it. The brain of this individ- 



