our “rudimentary third eyelid” has been inherited. His mention of birds as having a well developed third eyelid is not very helpful, because all evolutionists agree in excluding the birds from our line of descent. The reptiles are more promising candidates for the position of ancestors, but, as no trace of a third eyelid could possibly be left behind in the imperfect record of the fossiliferous rocks (soft parts like this having but slight chance of preservation), we do not really _know_ whether the palæozoic reptiles possessed this particular feature, or not. Nor can we argue from analogy and induction, because not _all_ modern reptiles are equipped with third eyelids. Hence the particular group of palæozoic reptiles, which are supposed to have been our progenitors, may not have possessed any third eyelid to bequeath to us in the reduced and rudimentary form of the plica semilunaris. If it be replied, that they _must_ have had this feature, because otherwise we would have no ancestor from whom we could inherit our semilunar fold, it is obvious that such argumentation assumes the very point which it ought to prove, namely: the actuality of evolution. Rudiments are supposed to be a proof for evolution, and not, _vice versa_, evolution a proof for rudiments. Finally, the basic assumption of Darwin that the semilunar fold is destitute of function is incorrect; for this crescent-shaped fold situated in the inner or nasal corner of the eye of man and other mammals serves to regulate the flow of the lubricating lacrimal fluid (which we call tears). True this function is secondary compared with the more important function discharged by the nictitating membrane in birds. In the latter, the third eyelid is a pearly-white (sometimes transparent) membrane placed internal to the real eyelids, on the inner side of the eye, over whose surface it can be drawn like a curtain to shield the organ from excessive light, or irritating dust; nevertheless, the regulation of the flow of lacrimal humor is a real function, and it is therefore entirely false to speak of the semilunar fold as a functionless rudiment.