98 



THE FUNDUS OCULI OF BIRDS 



the bird evidently possesses binocular vision 

 as he always looks straight ahead at objects 

 that he wishes to see distinctly. Plate XL, 

 page 159, furnishes an ophthalmoscopic view 

 of the right eye, erect image. The eye- 

 ground is orange-red stippled all over with 

 lighter orange dots. The lower half of the 

 fundus has a large number of minute, dark, 

 reddish-gray depots of pigment intermingled 

 with lighter dots; also, a great many cho- 

 roidal blood vessels run in a vertical direction 

 over the field of view on either side of the 

 optic entrance. They become more numerous 

 towards its lower periphery. 



The macula is placed, as in Owls generally, 

 on the temporal side of the optic papilla, 

 about one disc-length from its upper end 

 and half that distance to the temporal or 

 outer aspect of the fundus. It is a bright, 

 orange-red area surrounded by dark, red- 

 gray pigment, like a shadow. There is no 

 circular sheen around it, such as has been 

 noted about other avian fovese. 



The optic nerve-head is white, and along 

 its center appears a network of minute, 

 brown pigment dots clustering around the 

 sides of the pecten. A few white opaque 

 nerve fibres extend a short distance on either 

 side and about the upper end of the disc. 



The pecten, of the usual black-brown color, 

 extends the whole length of the disc. It is 

 rather straight in its upper half but is more 

 convoluted towards the lower part, where it 

 is quite massive and resembles a corkscrew. 

 This portion of the pecten comes markedly 

 forward towards the lens so that it more 

 nearly resembles the same organ in the 

 Burrowing Owl than in the Parrot; as indeed 

 the foregoing studies of the fundus oculi 

 lead unmistakably to the conclusion that 

 this bird belongs to the Owls rather than 

 to the Parrots. 



Coraciiformes 



European Kingfisher. Alcedo ispida. 

 (Figs. 99 and 113; macroscopic view.) This 

 remarkable background shows two exten- 

 sive, well-defined, circular macular regions, 

 both supplied with a large, deeply pigmented 

 fovea. The nasal macula is large and 



saucer-like. The fovea nasalis is surrounded 

 by a nebula formed of microscopic dots 

 that are, however, absent at the lower 

 nasal third of its margin. About the same 

 distance down and templewards from the 

 superior end of the disc, as the deeper fovea 

 is up and nasalwards, lies the secondary area 

 temporalis. [In the sketch the wall of the 

 globe is cut away to expose it.] This tem- 

 poral macular region is smaller and not so 

 well defined as the nasal fovea but it exhibits 

 a distinct pigmented centre surrounded by a 

 dotted ring. 



The large and curious pecten exhibits 17 

 double folds, two at the superior terminal 

 of the organ. These 34 convolutions are 

 very thin (like strips of paper), and through 

 the wide intervening spaces almost the 

 whole surface of the optic disc can be seen 

 and its outlines readily traced. The papil- 

 lary surface is dotted exactly like the sur- 

 rounding retina. The crest or free border 

 of the pecten is quite narrow, and caps the 

 pectinate mass in a wavy line. The naked- 

 eye view from above gives a picture much 

 like a fern frond. 



Laughing Kingfisher. Dacelo gigas. The 

 ophthalmoscopic appearances of this species 

 are pictured in Plate XLII, page 161. 



The fundus oculi is in general of a light 

 fawn-gray color mingled with irregularly 

 shaped, white or gray-white dots, except in 

 the neighborhood of the optic nerve where 

 it is orange-red, like the glow cast on the 

 sky by the setting sun. 



The optic nerve entrance is long and narrow; 

 it is white except along its central area, which 

 is orange-red striped with brown pigment 

 dots. A large number of opaque nerve 

 fibres run out on each side of the optic nerve 

 and at right angles to it. 



The pecten is very long and narrow and 

 has the appearance of a brown centipede. 



The macula is very conspicuous. About 

 half a disc-length from the upper end of the 

 nerve, towards the nasal side, is a small, 

 round, dark-brown hole, surrounded by a 

 very narrow, bright green ring. This circle 

 encloses a smaller area that is of a darker 

 gray and devoid of the dots seen at other 



