614 REPTILES 



The loss of the scleral ossicles in these animals is coupled with a 

 virtual disappearance of the ringwulst of the lens. These two losses are 

 clearly related to the noctumality of the crocodilians and their conse- 

 quent lack of need of much or any accommodatory capacity. The evolu- 

 tionary outbulging of the circumcomeal sclera upon the loss of its sup- 

 porting bones, and the inward shrinkage of the lens equator owing to 

 the thinning of the annular pad, have not however taken the ciliary body 

 entirely out of contact with the lens (as these same changes have done in 

 the mammals) . In the crocodilians the hundred-or-more greatly elongated 

 ciliary processes — they have been called 'tongue-like' — still contact the 

 thick capsule of the lens at its equator; and according to Beer and Hess 

 the accommodatory effort, though slight and exerted with extreme slow- 

 ness, is still sufficient to pull inward the circumcomeal zone of the sclera 

 and produce some bulging of the center of the rather flat anterior surface 

 of the lens.* The (wholly meridional?) ciliary muscle lies in the sclerad 

 lamina of the ciliary body, and is scarcely as well developed as in terra- 

 pins. Its fibers underlie the orbiculus, far distant from the limbus, with 

 their anterior ends attached to the inner surface of the scleral thickening 

 and their posterior insertions in the meshwork tissue close to the anterior 

 border of the chorioid. 



The accommodatory equipment centering around the ciliary muscle is 

 thus at a low ebb in the crocodilians, as in the turtles — but not for the 

 same reason: in the former, it is a logical consequence of an age-old 

 noctumaUty with its crude images and its indifference toward a precise 

 focusing thereof, while in the turtles it is owing to the fact that the 

 pupillary sphincter has taken on most of the work of increasing the curv- 

 atures and focusing power of the lens. The transversalis muscle, if ever 

 present in early crocodilians, is apparently lacking in living species. 



The deep pigmentation of the thick iris stroma is concealed in the 

 living animal by an anteriormost layer of lipophores which gives the 

 iris a lemon or cream color. The sphincter resembles that of turtles in 

 that its fibers are distributed throughout the whole width of the iris, 

 though concentrated only near the pupil. The posterior retinal layer is 

 heavily pigmented and cuboidal. The anterior is squamous and unpig- 

 mented. It may be radially contractile; but it is generally denied that a 

 dilatator is ever present in crocodilians — which may largely explain why 

 the alligator's pupil is so slow to open (p. 501). 



*The periphery of which surface only flattens the more during accommodation, being pre- 

 sumably kept from sharing in the 'bulge' by the pressure of the iris against it. 



