The cuckoo is quite a Bohemian among birds, and it is doubtless owing to its vagrant habits that there yet remain several points in its life-history which have to be cleared up. The most interesting of these questions are those which relate to its nesting and nidification. It was once thought that the cuckoo paired, but it is now known that the species is polygamous. The number of hens that constitute a harem is not known, but from the number of bachelor birds the males must greatly predominate over the females. Dissection conclusively proves that each female lays a series of eggs, and that these occur in the ovary in widely different stages of maturity. The older naturalists thought that the cuckoo laid its eggs actually in the nests of other birds, but it is now known that it conveys them thither in its bill. The egg of the cuckoo has been found in the nests of sixty different species, several of which are exceedingly small, and moreover domed. Among the sixty nests patronised were the unlikely ones of the butcher-bird, jay, and magpie--all either bird or egg destroyers. This may seem to reflect on the cuckoo's stupidity; and the bird certainly exhibits deplorable ignorance of the fitness of things when it deposits its egg in the nest of the diminutive goldcrest or the cumbersome one of the cushat. A goldcrest might conveniently be stowed away in the gape of a young cuckoo without the latter detecting that the morsel was much more than a normal supply. The nests in which the eggs of cuckoos are most frequently found are those of the meadow-pipit, hedge-sparrow, and reed-warbler. Now the eggs of these birds vary to a very considerable degree; and the question arises whether the cuckoo has the power of assimilating the colour of its egg to those among which it is to be deposited. Certain eminent continental ornithologists claim that this is so, but facts observed in England hardly bear out the conclusion. Brown eggs have been found among the blue ones of the hedge-sparrow, redstart, wheatear; among the green and grey ones of other birds; and the purely white ones of the wood-pigeon and turtle-dove. The cuckoo's egg is brown, and it must be admitted that the great majority of the nests which it patronises contain eggs more or less nearly resembling its own. There is a general family likeness about those laid by the bird, not only in the same clutch, but from year to year. Admitting that the eggs of the cuckoo as a species vary more than those of other birds, it is yet probable that the same female invariably lays eggs of one colour. This can only be surmised by analogy, though the one fact bearing on the question is where two cuckoo's eggs were found in the same nest, and which differed greatly. More might have been learnt from the incident had it been known for certain whether the eggs were laid by the same or different birds. There is a general tendency in the habits of animals to become hereditary, and it seems not unreasonable