264 



BRADLEY M. PATTEN 



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Fig. 22 A diagram showing that changes in the axial position of an organism 

 with non-parallel sensory areas, or eyes with tangents at the optical axes non- 

 parallel, change the relative amount of light intercepted by the sensory areas 

 of opposite sides. Lights same as in figure 21. 



sensitive surfaces are not parallel. In figure 22, a, the opposite 

 surfaces intercept equal amounts of light because their angles of 

 inclination are equal. In figure 22, b, the left area lies nearly at 

 right angles to the rays of light and its projection is equal to its 

 entire area, while the right side is inclined so that its projection 

 is much less than its area. Consequently the amount of light 

 acting on the bilateral photosensitive areas is different. In 

 figure 22, c, the case is similar to that of 22, b. The amount of 

 light received on the retina may not be exactly that operating 

 on the paratangential plane at the focal distance of the eye, but 

 it will be proportional to it. 



