152 LESLIE B. AREY 



The object of the work upon visual cells to be described in 

 this section parallels that stated for pigment, that is, to deter- 

 mine the effects of various temperatures on the myoid of rod 

 cells and of cone cells in normal fishes and amphibians. 



The apparatus and technique employed were similar to those 

 which were used in the experimentation upon pigment. Par- 

 ticular care was exercised at the termination of experiments 

 conducted in the dark to guard against the action of light on the 

 highly sensitive visual cells. In the fishes, measurements of 

 the cone myoid were made from the external limiting membrane 

 to the proximal edge of the ellipsoid, and in the frog, from the 

 external Umiting membrane to the proximal side of the oil drop 

 which is situated at the distal end of the ellipsoid. The lengths 

 of the rods were measured from the junction of the inner and 

 outer members to the external limiting membrane. Each value 

 given in the tables represents the mean measurement, in micra, 

 of many (12 to 24) individual elements. 



1. Fishes. (1) Ameiurus. Of the four fishes studied, the 

 cones of Ameiurus, in many ways, gave the least satisfactory 

 results. These elements are not located at uniform levels and 

 the differences between the elongated and shortened condi- 

 tion, when stimulated by extremes of temperature, are not strik- 

 ing to the eye. The additional fact that the cones, when maxi-. 

 mally shortened under the influence of temperature, never 

 closely approach the external limiting membrane makes these 

 animals rather unsatisfactory for certain kinds of experimental 

 work. 



Tables 1 and 2 present data for both rods and cones from typical 

 retinas at 5°C. and 25°C. in the dark. 



It will be seen that at the higher temperature the myoids of 

 both cones and rods lengthen (figs. 32, 33). Especially in the 

 cones is this response unmistakable. The lengths of the rod's 

 inner member, after subjection to the extreme temperatures, 

 varies within only a few micra, yet the relative change may be 

 25 per cent or more; moreover, since the mean ranges at the 

 extreme temperatures do not overlap, these differences are 

 presumably significant. If the length of the rod ellipsoid, 4 /x, 



