160 



LESLIE B. AREY 



ZMpfenliinge (von der Limitans externa bis zur Oelkugol im Ellip- 

 soid exclusive) betriigt im Durehschnitt maximal 0.034 mm., im 

 Mininuim 0.0169 mm." 



With apparatus and methods similar to those described in 

 connection with the experimentation upon frog's retinal pigment, 

 an attempt was made to discover the exact responses of the cone 

 myoid to high, medium, and especially to low temperatures. 



In table 10, which gives the measurements of visual cells 

 from a few typical preparations, it will be observed that the cones 

 are greatly shortened at 33°C. (fig. 36), but that at the other 

 temperatures they retain the elongated condition typical of 

 darkness (figs. 34, 35). ^^ Measurements of the cones gave two 

 modal lengths, which are approximately expressed by the figures 

 in the table representing the extreme values. The maintenance 

 of elongation at a low temperature is in agreement with Fujita's 

 ril) experiments, 1'" but is opposed to Herzog's conclusion, which 

 was apparently based upon exhaustive investigation. It is true 

 that the temperature of 0°C. which the latter worker used was 

 a few degrees less than the lower limit (3° to 5°C.) employed 



TABLE 10 

 Measurements from the retinas of eight Rana pipiens which had been kept at 3°, 14°, 

 19°, and 33°C., respectively, in the dark; the values are in micra and represent 

 measurements taken along axes coinciding with radii of the eyeball 



1* The actual values at medium and high temperatures vary somewhat from 

 those given by Herzog for R. temporaria (and R. esculenta?). 



13 This experimentation upon the retinal elements of the frog was practically 

 completed before Fujita's paper was known to me. 



