Structure of the Crystalline Lenses of Animals. 199 
tains five millions of fibres, and sixty-two thousand five hun- 
dred millions of teeth. A transparent lens exhibiting such a 
specimen of mechanism may well excite our astonishment and 
admiration ! 
The magnitude of the fibres and of their teeth varies in 
different animals. In the lens of a South American fish, for 
example, called the sheep-head, there are only 613 fibres in a 
spherical surface*; but it will be seen in a subsequent paper, 
that there are other animals in which the fibres are still more 
minute than those in the lens of the cod. 
By means of very fine microscopes, with high magnifying 
powers, I have succeeded in detecting the same structure in 
the lenses of birds and quadrupeds; but in these classes of 
animals it is much less distinctly developed than in fishes. 
The teeth are much shorter; and when the lens belonged to 
an aged animal, the toothed structure was extremely indistinct 
and irregular, and in some parts of the fibres it entirely dis- 
appeared. 
The fibrous structure represented in fig. 1, and in which 
the fibres converge to two opposite poles, is never found, in 
so far as my observations extend, in any of the Mammalia 
or Cetacea. It is the universal structure in the lenses of all the 
birds that I have examined; and though it is the most com- 
mon structure in fishes, it is pot the only one which they ex- 
hibit. In the following table, I have given the names of the 
different animals in whose lenses I have found the structure 
shown in fig. 1. 
FIsHEs. 
Cod. Loch-Leven Trout. Mackerel. 
Haddock. Turbot. Coal Fish. 
Serpent Fish. Sole. Gold Fish. 
Diver. Sayd. Great Lamprey. 
Mullet. Grey Dog. Bull-head. 
Herring. Flying Fish. Whiting, English. 
Holibut. Frog Fish. Pout. 
Fresh-water Fluke. Sea Cat. Dab. 
Salt-water Fluke. Eel. Plaice. 
Spirling. Pike. Lumpsucker. 
Birps. 
Cassowary. Turkey. Curlew. 
Albatross. Barnacle Goose. Chaffinch. 
Pelican. Sea Eagle. Thrush. 
Crane. Snowy Owl. Magpie. 
* The diameter of the lens was 1th of an inch, and there were 975 
fibres in an inch at the equator. 
