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Charles R. Stockard 



mated. The point is one which can only be proven by a number 

 of direct observations on all ages of cyclopean embryos and care- 

 ful study of sections; such a study has convinced me that no 

 fusion of the eyes takes place after they are once clearly given out 

 from the brain. 



It seems advisable for later stages to consider groups of embryos 

 showing various degrees of the cyclopean defect. 



b Incomplete Cyclopia; Double Eyes 



Under the term incomplete cyclopia may be considered indi- 

 viduals with eyes abnormally close together although separate 

 Among Fundulus embryos such individuals exist and a series of 

 stages connect these embryos with those in which the two eyes are 

 intimately connected or joined together. An individual of this 

 kind when sectioned will show the eyes as in Fig. 35. This sec- 

 tion is from a four day embryo, the two eyes are united in the 

 median line of the head and both are perfect eyes with a lens, 

 single retina and one optic nerve. The choroid coat as indicated 

 by the heavy line is just beginning to form. Fig. 36 shows a 

 section of two eyes which are more intimately united. This case 

 is the common "hour-glass" eye of cyclopia. The two eyes are 

 independent, except for their waist-like connection and each has 

 its lens, single pupil, retina and distinct opticus. The optic 

 nerve of the right component is seen entering the optic cross at 

 the base of the brain. The brain in this embryo is remarkably 

 perfect, as it is in many cyclopean monsters, and I see no reason 

 whatever for attributing the defect to a "single brain" or any 

 other gross malformation of the cephalic region. Many embryos 

 with deformed brains possessed two normal eyes and the converse 

 is true, many normal brains were accompanied by cyclopean eyes. 



Leaving the "hour-glass" eye, we find the double-eye shown 

 in Fig. 37, having a common optic chamber each half of which is 

 supplied by one component. Two lenses and two pupils are 

 present and generally two optic nerves, although they may run 

 so nearly parallel that the two are difl[icult to distinguish. A single 

 nasal pit is present in the embryo from which Fig. 37 is a section. 

 All of the cyclopean monsters possess two distinct auditory vesicles. 



