174 M. F. GUYER AND E. A. SMITH 
is always of coincidence and chance, and at the outset it is im- 
portant to realize how improbable it is that just the right chance 
variation would spring up at exactly the right time—that is, 
coincidentally with our treatments—to mislead us into believing 
that we had produced something that was destined to appear 
anyway in our different stocks of rabbits. 
Fig. 1 Profile view of rabbits to show natural bulging of the eyeballs of a 
normal rabbit (1) compared with one (4A5) in which the left eyeball is reduced 
in size, and one (6A4) in which it has practically disappeared. 
THE NORMAL EYE 
In order to understand the eye defects that have been induced 
in our stock, it is necessary to know the chief characteristics of 
the normal eye of the rabbit and something about its develop- 
ment. The eyeball of the rabbit, typically large and globular, 
measures about 16 mm. in diameter and protrudes beyond the 
contour of the head (fig. 1) so far as to be conspicuous. The 
outer or sclerotic coat is glistening white and contains no cartilage. 
The iris is also white with fine transparent radiations which 
