THE interesting suggestion recently made by Mr. Wynne-Edwards in these columns1 with respect to the inheritance of egg-colour in the parasitic cuckoos calls for a few remarks from the genetical point of view. Granting for the moment that the various types of egg-coloration in a polymorphic species such as Cuculus canorus are dependent upon a series of multiple allelomorphs, the location of such a series in the X-chromosome means that the nature of the egg laid by any hen must always depend upon the nature of the X-chromosome which she receives from her father. It is, therefore, rather misleading to state that the male cuckoo does not belong to the gens (in the Newtonian sense) at all. True, he may carry X-chromosomes characteristic of two distinct gentes, but since he must be supposed to determine the gens of all his daughters, it seems rather harsh to ostracise him as Mr. Wynne-Edwards would have us do.