184 W. BALDWIN SPENCER. 



certain of the rods become elongated ; this lengthening is con 

 fined in the former to those lying in the optic axis/.but in 

 Varanus takes place at two points, one of which, the most 

 prominent, lies in the optic axis, whilst the other lies to the 

 anterior side, each being connected with the entrance of a 

 separate nervous strand into the eye. 



Amongst the rods are scattered numerous spherical masses 

 of pigment. There is not the slightest indication of any struc- 

 tures lying internal to the rods embedded in pigment, such as 

 are described by de Graaf in Anguis ; on the other hand, the 

 internal limit of the layer of rods is so well marked as to 

 present the appearance of a definite membrane lining the 

 cavity. The latter was most probably filled during life by a 

 fluid, the coagulated remains of which are seen attached as an 

 irregular structureless coagulum to the inner ends of the rods. 

 External to the rods is a layer of finely punctated material 

 (Mo) apparently corresponding to the much narrower layer in 

 Hatteria. This layer, together with the rods, occupies as 

 nearly as possible one half of the breadth of the retina. In 

 this layer are situated spherical elements {n}), which in some 

 cases can be traced into connection with the rods ; no arrange- 

 ment in two or more rows, as in Hatteria, can be detected, 

 but they appear to be placed somewhat irregularly. External 

 to the molecular layer, the outer limit of which is somewhat 

 sharply defined, lie a series of spherical-shaped elements [n^). 

 The appearance of these as seen in section is given in fig. 6. 

 Some of the elements resemble those lying within the mole- 

 cular layer {n^), others have processes passing straight through 

 to the rods on the internal and the nerve- fibres on the external 

 side, whilst others again are connected with one another and 

 with the layers on either side by irregularly branching pro- 

 cesses. 



Certain of the nerve-fibres pass round behind the vesicle 

 and then enter the retinal elements, but apparently the greater 

 number are directly connected with the two above- described 

 bundles of elongated rods. 



Within the external layers of the retina are many large 



