CHANGES IN THE VISUAL CELLS OF THE FROG 



437 



of the tables, as the case may be. In such instances the process 

 of a\'eraging two groups of ten serves to mask this condition, 

 hence the tables, for the sake of compactness, are faulty in this 

 respect. 



The conclusion follows, therefore, that the photomechanical 

 responses of the frog's red visual-rod myoid arc in agreement 

 with those of other vertebrates in which changes have been 

 demonstrated. 



The older workers (Angelucci '84: '90; CIradenigro, 'So: and 

 Arcoleo '90) perhajis erred, either in not making actual measure- 



Meafsureinenl.s from lircidii-thrce dark-adapted nliiias of liann }ti/)icn.-^. The 

 values are in micra and represent measurements taken along axes coinciding 

 with radii of the eyeball. Each value for the length of the red rod myoid is the 

 mean obtained from twenty consecutively-placed elements 



