Effect of Aleohol and Ansestheties. 379 
Lewis’ illustrations are similar to Fig. 14 in so far as the course 
of the optic nerve is concerned. These experiments would seem 
to indicate that the direction taken by the optic nerve fibers is 
not firmly fixed but that they may pursue an almost reverse 
direction from that generally followed. Many of the eyes in the 
writer’s specimens show various conditions of this kind and he 
must agree with Lewis in the conclusion that 
It would seem to me impossible to explain these various conditions 
of the optic nerve on any other basis than that they are outgrowths of 
nerve cells of the ganglionic layer of the retina. 
Direct evidence is thus furnished for the outgrowth theory of the 
nerve fiber which has been so ably supported in the last few years 
by Harrison’s (’08) experiments. 
The present experiments warrant the following explanation 
for incomplete cyclopean eyes, or double eyes, when compared with 
the usual condition. 
In normal development the eye anlagen push out from the ven- 
tro-lateral borders of the brain and turn dorsally as indicated in 
the diagram, fig. 15 A. The abnormal individuals with two 
eyes facing the median plane also have them more ventrally 
situated in relation to the brain, and it may be supposed that when 
the eyes arose from the brain their formation was directed ven- 
trally instead of dorsally, fig. 15 B. This causes the eyes to hang 
below the brain and face one another as already shown in figs. 
4, 5, 6, 13, and 14, instead of turning dorsally and facing outward 
as in figs, 11 and 12. 
Similar conditions are also found in the development of a single 
eye. Fig. 1 shows an embryo with an eye on the right side only, 
yet this eye faces the median plane and is unusually ventral in 
position; it probably arose as indicated in the diagram fig. 15 D, 
where as other single-eyed individuals, the commoner type, have 
an eye looking out from the usual lateral position, fig. 15 C. 
From these conditions we may determine whether cyclopia is 
brought about by a failure of certain central tissues of the brain 
to develop, thus allowing the eye anlagen to come together as 
Lewis (’09) has suggested, or whether through a lack of develop- 
mental energy necessary for the optic cups to grow dorsally and 
