136 BLIND VERTEBRATES AND THEIR EYES. 



muscles, and orbital fat in Chologaster has in Amblyopsis become largely filled with 

 fat. There is no indication of fatty degeneration ; it is simply the accumulation 

 of fatty cells in the eye cavity. The eye is very small and lies on the floor of the 

 optic capsule. The infraorbital and supraorbital fat-masses described for Cholo- 

 gaster papilliferus are also large in Amblyopsis and form especially large masses in 

 front and behind the optic capsule. In Chologaster the brain extends forward beyond 

 the front of the eye, while in Amblyopsis the brain does not extend as far forward, the 

 anterior portion of the brain cavity being filled with fat. Attention may also be 

 called here to the presence and position of the suborbital bones which Kohl says 

 are represented in Troglichthys by the cartilaginous masses forming a hood over 

 the front of the eye. These cartilages (scl., fig. 49) are present in front of the 

 Amblyopsis eye, and it can readily be seen that they have nothing to do with the 

 suborbital bones (sub. 0). 



The adult eye of Amblyopsis with its appurtenances may now be taken up 

 seriatim. The eye occupies the lower part of the eye cavity. It is surrounded by 

 loose connective tissue, which is so associated with the eye that if contractions 

 occur through reagents, as frequently happens, a space is left between the eye 

 with its connective tissue and the septum forming the lower floor of the eye cavity. 

 Above the eye with its connective tissue is the large accumulation of fat mentioned 

 previously. From the eye to the inner wall of the orbit extends a continuation of 

 the connective tissue surrounding the eye. In this continuation of the connective 

 tissue the optic nerve and eye muscles extend. In the longest individual, 135 mm. 

 long, the eyes were 5 mm. from the surface of the epidermis. 



The shape of the eye together with the pigment variously scattered in the con- 

 nective tissue associated with it is very variable, differing from subspherical in the 

 smaller individuals to long spindle-shaped in the old. Considerable difference 

 is found in the shape of the eye itself. See table of measurements, page 144. 



Pigment is found in very variable quantity and variously scattered in the con- 

 nective tissue surrounding the eye. The amount of this pigment seems to vary 

 inversely with the amount of pigment in the eye itself and to increase with age. 



As Wyman has stated and figured, eye muscles are present in Amblyopsis, 

 but, contrary to his statement, they are the homologues of the normal eye muscles. 

 Not all preparations are equally good for tracing the muscles. They are best 

 demonstrated in heads treated entire by Golgi's method and sectioned in celloidin. 

 While the muscles have been noted in a variety of preparations the description will 

 be drawn from those treated by Golgi's silver method and stained at times with 

 haemalum or Biondi-Ehrlich's 3-color stain. 1 



In one individual the upper rectus and upper oblique muscles are inserted 

 together on the upper median surface of the eye, or more exactly on the upper 

 posterior angle of the upper scleral cartilage. The lower oblique is inserted opposite 

 this place. From these places the oblique muscles extend inward and forward. 

 The origin of the lower oblique is 0.72 mm. in front of its insertion, while the larger 

 upper oblique extends a little farther forward, being inserted 0.85 mm. behind its 

 origin. It takes its origin in the projecting angle of a cartilage above and in advance 

 of the origin of the lower oblique. In the inner part of the orbit a small muscle 



1 Golgi's method did not give the desired results for nervous structures, but by staining with the above 

 methods the material was found excellent for general purposes. 



