228 MR. J. W. HULKE ON THE CHAMELEON'S RETINA. 



fovea. Besides which the great proportional number of cones in the fovea is attended 

 with a corresponding increase in the number of the outer granules. 



Conal Layer. — The cones become thinner, longer, and more numerous from the peri- 

 phery to the centre of the retina, i. e. of the fovea. At the centre of the fovea they 

 reach the extraordinary length of 3^". In fresh specimens the characteristic bead in 

 the outer end of the inner segment of the cones here was conspicuous, though very 

 minute. 



A careful study of many sections has convinced me that the cones stand vertically on 

 the choroid ; the primitive fibres proceeding from them to the outer granules do, how- 

 ever, incline on all sides from the centre of the fovea ; and the bundles of the cone-fibre 

 plexus, as also the oblique fibres in the inner granule-layer, are similarly deflected. 



Enumerated briefly, the peculiarities of the fovea consist in the attenuation of the optic 

 nerve, ganglionic, granular layers, and cone-fibre plexus, from its margin towards its 

 centre ; in the absence of these layers at the centre ; in the great slenderness and length 

 of the cones ; in the deflection of the primitive cone-fibres and of their continuations 

 in the outer and inner granule-layers from the centre towards the periphery ; and in the 

 maximum development of all the layers, excepting the bacillary, at successively 

 increasing distances from the centre of the fovea in their order of superposition from 

 the outer to the inner surface of the retina. 



Explanation of Plate. 

 PLATE XIX. 



Fig. 1. An enlarged view of the Fovea centralis in the fresh retina. 



Fig. 2. Cones from the Fovea : a, the outer ; h, the inner segment. 



Fig. 3. Cones from the periphery of the retina: a, the outer segment; b, the inner 

 segment containing, d, an outer granule, and produced inwards as a primitive 

 fibre through the membrana limitans externa ; c, intended to mark this latter 

 (the horizontal line), has been placed too high by the artist. 



Fig. 4. A vertical section near the Fovea parallel to a, the bundles of the cone-fibre 

 plexus ; b, primitive fibres passing from these bundles through d, a gi-anular 

 stratum, into the inner granule-layer ; c, the outer vertically-radial connective- 

 tissue fibres. 



Fig. 5. A vertical section through the outer^layers near the Fovea. Only the connective- 

 tissue frame is represented : 1, the bacillary layer ; 2, the outer granule- 

 layer ; 2', the cone-fibre plexus ; 3, a granular stratum representing the inter- 

 granule-layer ; c, the membrana limitans externa ; /, the trunks of the outer 

 vertically-radial connective-tissue fibres; g, their outer ends, branching and 

 terminating in the membrana limitans externa (the artist has drawn these too 

 thick) ; h, the branching inner ends of the fibres forming the intergrauule- 



