LIGHT-SENSE 49 



All children instinctively dread darkness and many per- 

 sons can never free themselves from such dread throughout 

 their lives. O. G. S. Crawford, writing in a recent number 

 of the CornkiU Magazine on 'Prehistoric Instincts," says: 



'Primitive man is an animal that lives and works by day. 

 His habits are not nocturnal, and he seldom by choice goes 

 forth from his lair during the hours of darkness. This 

 love of daylight, and the corresponding aversion to dark- 

 ness, is probably due to the great reliance he places upon 

 sight; but, of course, the order of causation may have been 

 reversed. We do not, however, find it in dogs, which rely 

 on ear and nose. However this may be, there can be no 

 doubt about the existence of an instinctive dislike of dark- 

 ness in all of us today. This dislike is the pale survivor of 

 a very real and acute instinct of fear innate in us, which 

 dominates our childhood with all the vigor of its original 

 force. ' 



Primitive man, a mighty hunter by day, through the 

 absence of a tapetum became a coward by night. A some- 

 what parallel instance may be referred to occurring among 

 birds. They have no tapetum lucidum in their choroids, 

 but in the retinae of nocturnal birds rods are found to pre- 

 dominate very largely over the cones, while in the retinae of 

 diurnal birds the reverse condition is met with, the cones 

 in them being far more numerous than the rods. The small 

 diurnal birds, sparrows, chaffinches, redbreasts and such 

 like, as soon as dusk begins to approach, seek concealment 

 in bushes and hedges, where they will be safe from the dreaded 

 attacks of the night owl. Should the owl prolong his hunt- 

 ing expeditions to such a distance that daylight overtakes 

 him before he can return to his usual retreat, he becomes 

 dazzled, is unable to proceed, and has to remain where he 



is until darkness again ensues. If during the daylight he 

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