380 THE EYE IN EVOLUTION 



. nocturnal life in holes or burrows which it often shares with a petrel, 

 and is found only in some small islands in the Bay of Plenty off the 

 coast of the North Island of New Zealand where, however, it is tending 

 to become extinct (Fig. 459). 



The eyeball as a whole, studied originally by Osawa (1898) and 

 later by Dendy (1910), Howes and Swinnerton (1903) and Mann 

 (1932-33), resembles closely that of the lizard adapted for nocturn- 

 ality ; its essential features are the large cornea and lens, the reduced 

 accommodative apparatus, the slit-pupil, the rod-rich avascular retina 

 with feiv insignificant cones, and the presence of a fovea. 



Fig. 460. — The Ciliary Region of Spbenodox. 



A diagram from Walls showing cm, ciliary muscle ; co, conjunctiva ; 

 cs, ciliary venous sinus (containing a nerve shown in black) ; I, lens ; ot, ora 

 serrata ; r, annular pad ; sc, scleral cartilage ; so, scleral ossicles ; z, zonule. 



The GLOBE is large with a marked sclero -corneal sulcus ; the 

 cornea is strongly curved with a thin two-layered epithelium ; and 

 the sclera is provided with an extensive cartilaginous cup and a ring 

 of 16 to 17 ossicles. 



In the choroid there are peculiar spheroidal cells, heavily pigmented 

 and with central nuclei, which form a dense aggregation opposite the 

 fovea. The ciliary body, like that of the lizard, shows no ciliary pro- 

 cesses, and the circular ciliary venous sinus, lying on the inner aspect 

 of the sclera at the level of the root of the iris, is very large with an 

 annular nerve on its posterior aspect (Fig. 460). The ciliary muscle 

 is feebly developed. The iris is brightly coloured with a layer of 

 chocolate-coloured chromatophores through the apertures of which 

 are seen coppery lipophores and silvery iridocytes ; the vascular 



