50 CHELTENHAM COLLEGE NATURAL HISTORY SOCIETY. 
SUMMARY OF A LECTURE ON « THE EYE,” 
BY DR. FERGUSON, 
N February 2oth, at 5.30 p.m., Dr. Ferguson in 
the presence of the Principal and several of the 
Masters gave a most entertaining and instructive 
Lecture to the Natural History Society on the 
Eye. The presence of vision, he said, was 
related to light and use. The fishes and insects 
of the great dark Caves of Kentucky and Cuba 
were blind, and many deep sea fishes were even 
—— eyeless. Even perfect eyes would become 
blind unless kept in order by use. There was sight throughout the 
whole animal series, beginning with the simple imbedded lenses of 
sea anemonies and jelly fishes. 
Then the structure of the human eye was described, and it was 
especially noticed that short-sighted people’s eyes were too long from 
front to back and long-sighted people’s too short. The mode 
by which the eye focuses near objects was specially dwelt on; this 
being effected by the natural elasticity of the lens, which is brought 
into play when the flattening influence of its suspensory ligament is 
lessened by the forward drag of the internal ciliary muscle. 
The retina of the eye was described at length, more particularly 
_ its most important part, the rods and cones. No real retina, indeed, 
without rods or cones. The cones have probably most to do with 
_ the colour sense, as they are absent in most nocturnal animals. 
} Though with two eyes we see only one image, this is mainly 
_ because each right nerve of sight supplies the right halves of both 
‘ eyes, and each left nerve the sight of both left halves. The pictures on 
_ our retina are inverted, but still we see all things upright. Thus, 
_ because we see the objects themselves, and not in our eyes, but in 
_ our brains, and judge of their positions by the direction from which 
_ their rays reach us. 
: Then a brief description, with lantern illustrations, was given of 
“several other types of eyes; those of the snail, the nautilus, the 
Cuttle-fish, the worm, and the insect. Eyes may be found in 
unexpected places: in our shrimp, on the legs ; in the deep sea-fishes 
