One somewhat similar case does indeed occur among the Mammalia, two singular African animals, the Aard-wolf (Proteles) and the hyæna-dog (Lycaon), both strikingly resembling hyænas in their general form as well as in their spotted markings. Belonging as they all do to the Carnivora, though to three distinct families, it seems quite an analogous case to those we have imagined; but as the Aard-wolf and the hyæna-dog are both weak animals compared with the hyæna, the resemblance may be useful, and in that case would come under the head of mimicry. This seems the more probable because, as a rule, the colours of the Mammalia are protective, and are too little varied to allow of the influence of local causes producing any well-marked effects. When we come to birds, however, the case is different; for although they do not exhibit such distinct marks of the influence of locality as do butterflies--probably because the causes which determine colour are in their case more complex--yet there are distinct indications of some effect of the kind, and we must devote some little time to their consideration. One of the most curious cases is that of the parrots of the West-Indian Islands and Central America, several of which have white heads or foreheads, occurring in two distinct genera,[42] while none of the more numerous parrots of South America are so coloured. In the small island of Dominica we have a very large and richly-coloured parrot (_Chrysotis augusta_) corresponding to the large and richly-coloured butterfly (_Papilio homerus_) of Jamaica. [42] _Pionus albifrons_ and _Chrysotis senilis_ (C. America), _Chrysotis sallæi_ (Hayti). The Andaman Islands are equally remarkable, at least six of the peculiar birds differing from their continental allies in being much lighter, and sometimes with a large quantity of pure white in the plumage,[43] exactly corresponding to what occurs among the butterflies. [43] _Kittacincla albiventris_, _Geocichla albigularis_, _Sturnia andamanensis_, _Hyloterpe grisola_ var., _Ianthœnas palumboides_, _Osmotreron chloroptera_. In the Philippines this is not so marked a feature; yet we have here the only known white-breasted king-crow (_Dicrurus mirabilis_); the newly discovered _Eurylæmus steerii_, wholly white beneath; three species of Diceum, all white beneath; several species of Parus, largely white-spotted; while many of the pigeons have light ashy tints. The birds generally, however, have rich dark colours, similar to those which prevail among the butterflies. In Celebes we have a swallow-shrike and a peculiar small crow allied to the jackdaw,[44] whiter than any of their allies in the surrounding islands; but otherwise the colours of the birds call for no special remark. [44] _Artamus monachus_, _Corvus advena_. In Timor and Flores we have white-headed pigeons,[45] and a long-tailed flycatcher almost entirely white.[46] [45] _Ptilopus cinctus_, _P. albocinctus_. [46] _Tchitrea affinis_, var.