3l8 Charles R. Stockard 



ual is abnormal and the eye is out of the median hne. The em- 

 bryo of Fig. 48 was abnormal with the brain distorted so that the 

 Cyclopean eye was slightly to one side and far out beyond the head. 

 The retina differentiates into layers but the lens lies out of the 

 central position, and would be unable to function efficiently. 



A peculiar condition is found in the embryo from which sec- 

 tions shown in Figs. 49, 50 and 51 were taken. This very small 

 eye was again in an extremely anterior position, though almost in 

 the median line. The lens is as large as the optic cup and pro- 

 trudes far out beyond its edge. Fig. 49, the most anterior section 

 of the three, passes through the great circle of the spherical lens and 

 shows it entirely outside the optic cup. On passing back in the 

 series to where the lens is less in size, we reach the anterior edge 

 of the optic cup and choroid coat. Fig. 50. Continuing back in 

 the series of sections, the lens disappears and the optic cup alone 

 is shown in Fig. 51. The lens in this eye is clearly too large for 

 the accompanying cup as was also the case with the two eyes just 

 described. The size of these lenses is, therefore, independent of 

 the size of the optic cup. Lewis' ('04) idea that the cup regulates 

 the size of the lens does not apply to these embryos, nor does the 

 rule for the amphibian that the origin of the lens is dependent 

 upon the influence of the cup. 



A step beyond this condition of a small anterior eye with its 

 ill-fitting lens may be illustrated by an embryo in which the eye is 

 a minute choroidal sphere buried in mesenchyme below the brain 

 and in the median line. In life this specimen seemed entirely 

 eyeless, but sections showed this small eye-like structure (Fig. 

 52) in the position typically taken by a cyclopean eye. Such 

 cases as this emphasize the necessity of sections in order to cor- 

 rectly interpret the conditions of cyclopia and conclusions based 

 only on superficial studies are necessarily unreliable. The nasal 

 pits were in the normal lateral position. Passing back in the sec- 

 tions to the region usually occupied by the two eyes, it will be seen 

 that on one side a typical lens occurs (Fig. 53). The lens is well 

 differentiated and completely isolated from all connections with 

 either nervous or eye tissue. A band of muscle is seen in the 

 figure to touch the inner edge of the lens. 



