STRUCTURE OP THE CRYSTALLINE LENSES OF ANIMALS. 
37 
the Perameles nasuta may have its lens formed according to another class of struc- 
tures which will afterwards be described. The fibres of the lens of this animal are 
extremely small, and the teeth upon them, though very minute, are distinctly seen 
with a high magnifying power. 
The structure indicated by two septa is perceived very distinctly in the lens of the 
Cobra Capella and the Lacerta Gecko, and indistinctly in that of the Stellio Gecko and 
the Frog. The lenses of the Cobra Capella and the Lacerta Gecko are nearly sphe- 
rical ; and the laminae of the lens of the Stellio Gecko are composed of a fibrous tissue, 
and not of fibres united by teeth. 
In the following Table I have given the names of the different animals whose lenses 
have the structure shown in fig. 1. 
Quadrupeds. 
Hare. 
Rabbit. 
Reptiles. 
Perameles nasuta (one side) 
Cobra Capella. 
Frog (probably). 
Lacerta Gecko. 
Alligator. 
Fishes. 
Stellio Gecko (probably). 
Salmon. 
Tench. 
Hickory Chad. 
Dolphin. 
Carp. 
Cavala (Georgia). 
Shark. 
Perch. 
Stingarie. 
Porpoise. 
Sturgeon. 
Skip-jack. 
Skate. 
Gudgeon. 
Chad. 
Thornback. 
Cat-fish. 
Black-fish (Georgia). 
Boneto. 
Par. 
Fish from Singapore. 
Dog-fish. 
Sword-fish. 
Red Trout. 
River Trout, common. 
Sheep-head. 
1. Hare. — I have examined the lenses both of the common hare and the blue 
mountain hare, which have the same structure. In observing their action upon po- 
larized light, I find that they depolarize two series of luminous sectors, the inner 
sectors having the negative structure like calcareous spar, and the outer sectors the 
positive structure like zircon. In order to perceive the inner sectors, the lens must be 
taken out of the eye with great care, and subjected to no pressure, and the polarized 
light must be transmitted through its axis. 
2. Rabbit . — The lens of the rabbit resembles that of the hare in its general pro- 
perties. The cornea of a rabbit depolarized faint sectors of light, and its polarizing 
structure was negative. 
3. Perameles nasuta . — When the lens of this animal was taken out of the spirits 
which preserved it, and the outer coat removed, its fibres were crossed perpendicu- 
larly by irregular and slightly serrated lines, much more distinct than the fibres. As 
