THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 



75 



Colymbiformes 

 Pacific Loon. Gavia pacifica. The 

 writer has never been able to examine more 

 than one individual of this species, or any 

 other Diver. He was obliged to use the 

 ophthalmoscope, with little protection from 

 the blazing sun of a Californian noon-day, 

 upon a recently dead bird. The examination 

 was necessarily incomplete. The fundus was 

 light gray, dotted over with dark pigment 

 granules; the pecten was large and there 

 was a well-marked porus opticus. 



Sphenisciformes 



Black-footed (Cape) Penguin. Sphen- 

 iscus demersus. The eyeground of this 

 species is depicted as Plate XIV, on page 133 

 of this monograph. 



The dominant color of the fundus is bright 

 red shading to crimson. It is generally 

 stippled with minute, dark-red and orange 

 dots, much like grains of sand. About a 

 disc-length from the upper end of the optic 

 disc these dots become grayish-white; indeed, 

 the fundal coloration is distinctly gray 

 towards the upper half of the eyeground. 

 In a region the same distance towards the 

 temporal aspect of the background may be 

 seen a cluster of pinpoint, brilliant, white 

 dots in the macular area. Penguins use the 

 nictating membrane very frequently when 

 light is thrown on this part of the eyeground. 



The optic disc exhibits enamel-white edges; 

 it is hollowed out in the centre, like a sewing- 

 machine shuttle. Running across this con- 

 cavity and at right angles to the margin of the 

 disc one sees a large number of gray fibres. 



The pecten lies along the centre of the 

 nerve, where it is orange-red in color and 

 mottled with minute, brown pigment dots. 

 The pecten has the usual dark chocolate- 

 brown shade. It is of spiral form, like a cork- 

 screw laid on its side. A few slender opaque 

 nerve fibres are visible on each side of and at 

 right angles to the disc. 



Procellariiformes 



Dark-bodied Shearwater. Puffinus 

 griseus. (Figs. 122 and 85.) The fundus of 

 this species, as seen by the naked eye, 



exhibits a darkly outlined band, widest at 

 the nasal extremity and at its middle, with 

 irregularly pigmented borders and a lighter 

 center, runs across the field of view from 

 one periphery to the other. Its central 

 third is shown as uncolored except for a 

 line of pigment that divides it into two equal 

 strips — thus constituting a linear fovea, the 

 circlet seen in some other band-like areas 

 being absent. 



There are 20 convolutions in the rather 

 short, thick pecten. These double coils are 

 so divided where they join the compara- 

 tively narrow sloping crest that glimpses 

 may be had of the nerve head below. The 

 keel covering the upper portion of free border 

 is prolonged into a blunt, rounded process, 

 partly formed by the larger and higher 

 posterior "teeth" or segments of the mar- 

 supium. 



What has by the writer been termed the in- 

 fulapapillary angle is 55°. This is made by 

 projecting the major axis of the papilla to meet 

 the lower margin of the transverse sensitive 

 area of acute vision. 



Alciformes 



Pigeon Guillemot. Cepphus columba. 

 (Figs. 23 and 82.) The background of this 

 species, when viewed macroscopically, re- 

 veals a narrow, uniform, pigmented retinal 

 band that stretches across the field of view 

 from one periphery to the other. At a point 

 where it approaches the superior end of the 

 papilla is placed a circular area (the fovea) 

 whose diameter is twice the width of the 

 band. 



The pecten is remarkable in that it rarely 

 obscures a view of the margins of the long, 

 broad, ovoid, optic nerve-head, which has its 

 pointed extremity upwards. There are 30 

 convolutions in the pectinate mass, and 

 occasional views can be had of the papilla 

 through clefts in it. The ridge-like, free 

 border of the pecten is linear for a third 

 of its length below but follows the undula- 

 tions of the convulutions beneath it until 

 it reaches its superior end. The double 

 folds in this organ are longest and most 

 voluminous at their middle, where the 



