At Cape Adare the light grey "silvery" coloured chicks mentioned by Dr. Wilson were by no means uncommon; in fact, quite a large proportion of the chicks had very light-coloured down. This is shown in some of the specimens I brought back to the British Museum. (B) Variations. Variations occasionally are met with in the plumage and soft parts of Adélies. The least rare of these consist of tufts of white feathers amongst the black plumage of the head. Several specimens so marked were seen at Cape Adare during the summer of 1911-12. When these white tufts were present the feathers comprising them were usually longer than the black feathers among which they appeared, so that they stuck out in an untidy manner, and were very conspicuous. In marked distinction to the slight variations above described were the three "Isabelline" varieties that I preserved, and are now to be seen in the British Museum collection. As these variations are very startling, and of the greatest interest, I give below a full description of their plumage and soft parts. _First specimen_ captured on the Cape Adare rookery on November 4, 1911. _Iris_, light brown. _Eyelids_, white. _Bill_, light brown. _Feet_, white. _Claws_, light brown. The whole of the area covered by black feathers in the normal bird was covered by those of a very light fawn, somewhat darker on the neck and shoulders than elsewhere. _Sex_, male. _Second specimen_ captured on November 14, 1911. _Iris_, light brown. _Eyelids_, white. _Bill_, light brown; mandible, blackish on dorsum; maxilla, blackish on cutting edges. _Feet_, white on both surfaces. _Claws_, light brown. In place of the black feathers of the normal bird, there was a fawn-coloured plumage, darkest on head and neck; lightest at bottom of back, back of flippers, and on shoulders. _Sex_, female. _Third specimen_ captured on December 23, 1911. _Iris_, light brown. _Feet_, browny white. _Claws_, brown. _Bill_, brown; very dark on dorsum of mandible. _Eyelids_, white with a pink tinge. In place of the black feathers of the normal bird, this specimen had those of a very light cream colour: in fact very slightly darker than the white area but deepening in shade to light fawn on the head, neck, and shoulders. _Sex_, male. The second specimen had mated with a normal cock. In each case the Isabelline birds were very much more docile than the normal forms. For instance, they did not struggle when picked up, as the others would have done, and the third specimen, when brought into our hut, gazed around with curiosity and apparent contentment, and showed not the least resentment at its captivity. A normal bird would have struggled and fought to the last extremity. Each bird was killed with chloroform. So carefully did we keep the entire rookery under observation that I do not think it likely there were any more Isabelline forms. Thus we can conclude 3/750000 roughly represents the proportion of Isabelline forms among the species.