No. 3.] VISUAL CELLS 'IN VERTEBRATES. 623 
4. The polarization is like that of the rod under ordinary 
conditions; 7. ¢., the cone axis lies in the positive optical 
direction, but the reaction is less decided. The evidence indi- 
cates that there are fibrillar elements present not responding 
to the predominating reaction. 
5. No intermediate plate was observed in the cones of 
Necturus. 
6. The ellipsoid differs slightly from that of the rod cell 
in 1ts reaction to stains and in its form, which is more elong- 
ated in an axial direction. 
7- The paraboloid seems essentially like that of the rods. 
The separation between it and the nucleus is greater in the 
cones than in the rods. 
8. The nucleus of the cone differs from that of the rods 
in being an ovate spheroid with its small end distal. In 
other respects the nucleus of the cone cell seems to be like 
that of the rod cell. 
DouBLE Cone CELLS. 
I. The double cones consist of two complete cone cells 
united along their sides from their nuclei to their ellipsoids. 
The two individuals are evidently specialized for different 
functions, since homologous parts in each differ in form and 
staining properties, excepting perhaps the outer segments, 
which are not directly connected. 
2. The far-cone retains the essential structural characters 
of the ordinary cones and evidently has the same function 
as these. 
3. The near-cone is so unlike its fellow as to make it 
probable that its function is different. The nuclear relations 
suggest that the near-cone has a specialized trophic function 
for the pair, while the special development of fibrils in the 
far-cone and other considerations would indicate that its 
function was more highly developed along the line of that 
of the single cones. 
