24 
3. Probably every bird—carinate and acarinate—possesses a pec- 
ten. This is quite as true of the Apteryx (long thought to be with¬ 
out one) as it is of our common wild birds. The size, shape and 
relations of the pectinate body to the other ocular structures are so 
varied, and their appearances, as determined by the ophthalmoscope 
during life are so constant in each wild species, that the back¬ 
ground picture of a particular wild bird furnishes certain data for 
a classification of quite as much value as the variations in any other 
organ. 
4. The refraction of most wild birds is simple hypermetropia; 
of domestic species, hypermetropia, or myopia, with astigmatism. 
5. The postmortem appearances of birds’ eyes are decided^ mis¬ 
leading, especially as to the shape and size of the eyeball and the 
relations of the parts in the interior of the globe. 
b. The range and rapidity of accommodation in birds far exceed 
that of man or other animals, and the accommodative and refrac¬ 
tive apparatus is much more complex than in other sub-kingdoms. 
7. The areas of distinct vision in birds are peculiar to them. In 
a single fundus may be present one or two fovese, or one, two or 
three visual areas, thus enabling the bird to obtain the sort of vision 
most suited to its needs. 
8. The color sense in birds is ver}^ acute, as shown by the great 
preponderance of cones in the retinal elements. 
9. A number of congenital anomalies in man are but the evolu¬ 
tionary remains of birds’ organs. For example, the posterior len- 
ticulo-capsular opacities, described by Mittendorf ? and the human 
persistent hyaloid artery are undoubtedly unabsorbed pectinate 
tissues. 
10. An extended study of the ocular fundi of birds may not only 
throw light upon the classification of doubtful species and so prove 
useful to the zoologist, but may possibly illuminate some of the 
problems of human ophthalmology. 
