As an ex-scientist and now full time homemaker and mother of 2 children and with a son with COMPLETE ACHROMATOPSIA, a rare congenital recessive gene condition in which only his rod photoreceptor cells are functional in both his retinas, so he has excellent night vision but is blinded by daylight since the rod cells are soon 'blinded' by excess light and not having any functional cone cells(they may be there but they don't function) he is totally colour-blind-it occurred to me that in effect he is like a 'nocturnal animal' relying only on his rod cells for vision. In fact he wears darkened treatment lenses all the time and prefers to work in a dimly lit environment.Perhaps what I am suggesting is nonsense but it occurred to me that TOTAL ACHROMATS (also called Achromatopes) are the human equivalent of nocturnal creatures and it occurred to me whether Total Achromats, showing no functional cone activity, may also have adapted their rod cells in the same way as those of true nocturnal animals that you describe in your paper.Of course one could only study this idea if one had access to 'total achromat' corpses to dissect out the retinal cells-a large source of such people all bearing the same genetic defect can be found on the Pingelap islands in the pacific ocean ,as mentioned in the book entitled 'the island of the colourblind' by the famous Dr Oliver Sacks (a neurologist and neuroanthropolist)who went to that island with the late norwegian Dr Knut Nordby ( a vision scientist from Oslo university). I and my son had the priviledge of meeting the latter gentleman at the 1st Italian Achromatopsia organisation meeting. Dr Knut Nordby was the most studied total achromat of all time and I expect he gave hs eyes for medical research when he died.It is already known that there are genetic differences between European,pacific island and Amerian Achromats but the defects all seem to be in the signal transduction pathways into the cells( see Dr Lindsey Sharpe's work-also read his book 'Night Vision' in which Dr Knut b Nordby also writes a chapter on his condition. \nInterestingly,wheras my son has excellent night vision and daytime blindness, I am miopic and so tend to suffer the opposite i.e.I have night time blindness and good day time vision ,and a late uncle of mine, who was an excellent RAF pilot (partly because of his excellent day time vision )sadly had to leave the airforce due to suffering night time blindness.!!!