188 W. BALDWIN SPENCER. 



wanl on either side in front of the eye just as in V. giganteus. 

 The figure shows the specialisation in the connective tissue above 

 the eye, and the entire absence of pigment-bearing cells in the 

 same position, though they are present on both sid es in the section . 

 Lens, — The lens has very much the same structure as in V. 

 giganteus, being distinctly cellular with well-marked nuclei, 

 forming in section a double or triple row from side to side, the 

 cells appearing to run the whole breadth, whilst in the middle of 

 the lens a great mass of pigment is deposited in the line of the 

 optic axis. The pigment masses are spherical on the external, 

 and more rod-like on the internal surface. 



Structure of Retina. — The specimen being preserved in 

 spirits without special reference to histological work, it was 

 somewhat difficult to make out many points with regard to the 

 structure of the retina. The rods are well developed and pro- 

 minent, lining the cavity of the vesicle, and having their long 

 axes arranged as indicated in the figure, those in the optic axis 

 being at right angles to the external surface, the eye itself being 

 immovably fixed, so as to look directly upwards. They are em- 

 bedded in pigment, and none amongst them appear to be specially 

 elongated (associated, doubtless, with the absence of connection 

 with any nerve, such as is present in V. giganteus or Hatteria). 

 No trace of any definite structure internal to the rods can be seen. 

 External to the rods lie a series of spherical-shaped elements 

 {n'), corresponding, presumably, to the same in Hatteria and 

 V. giganteus, and at intervals amongst these can be detected 

 spindle-shaped bodies, which, together with the former, stain 

 easily (with hsematoxylin and borax-carmine). Both these lie 

 within a layer, consisting, as in V. giganteus, of finely-punc- 

 tated material, whose external limit is well defined. It is difficult 

 to ascertain precisely the structure of this particular layer, which 

 in these two (as well as in other forms) has the appearance of a 

 ground substance, in which lie the external ends of the rods and 

 the spherical elements, but its constant presence and character 

 renders it unlikely that it is the result simply of reagents ; it is 

 here called the molecular layer, but may, perhaps, differ in nature 

 from the layer to which the same name is applied in Hatteria. 



