PITTAS. 467 



or ground-thrushes, arc a group of insectivorous birds wliicli inhabit the forests of 

 the e:;stern tr()])ics, and arc generally adorned with brilliant and strongly contrasted 

 colors. The rich blues and crimsons, the delicate greens, yellows, and i)ur])Ics, the 

 velvety black and pure white (throe of which tints at least generally adorn each spe- 

 cies) remind one of the tanagcrs of South America; and, in fact, these two groups 

 are almost the only ones which have no one characteristic tint or style of dress, but 

 whose different species seeni free to adorn themselves witli the brightest hues from 

 Nature's laboratory. There is, however, this difference, liiat, whereas the tanagersare 

 a dominant group, abounding in genera, species, and individuals, over a very wide 

 area, and presenting to our view much \aricly of form and almost every possible com- 

 bination of colors, the pittas are a small and probably decreasing genus, with but slight 

 modifications of form, and alike poor in species and in individuals. They inhabit a 

 district which has been recently broken up into many fragments, and which seems to 

 have been, during long ej)ociis of the past, in an unstable and ever-changing condition. 

 With the exception of the West African P. angolensis, which belongs to the same 

 section of the genus as the species from India described above, all the jjittas belong 

 to the Oriental and Australian regions, being most abundant in the Malay Archipelago, 

 about e(iually divided between the two regions. They attain, however, their maxi- 

 mum of beauty and v.ariety in the large islands of Borneo and Sumatra, from whence 

 they diminish in numbers in every direction, one species being found in North 

 China, and only a few in Australia. It is interesting to remark that the species which 

 are most alike form a section which spreads over the whole range of the family, 

 the African and Chinese as well as one of the Australian species all belonging to 

 the same grou]i distinguished by its comparatively plainer colors, while the small 

 islands of the Malay Archipelago show great contrasts in coloration, each island being 

 usually inhabited by a distinct species. The following remarks of Dr. Wallace 

 illustrate bo forcibly several cardinal jioints in the (|ucstion as to the influence of 

 geographical distribution, or the origin of species, that we cannot refrain from quot- 

 ing him in full. 



"It is," he says, "interesting to remark that two species of the same group scarcely 

 ever inhabit one island ; where two or more s])ecies are found in an island, they almost 

 invari.ably belong to as many distinct sections of the genus. This illustrates Mr. 

 Darwin's theorj- of the extermination of closely allied forms by the more dominant 

 race, and also of the effects of intercrossing in keeping uji tlie uniformity of a species 

 over a wide area. It thus happens that it is on the continent that the species have the 

 widest range, though the varieties of physical condition in India, from the Himalayas 

 to Ceylon, must certainly be greater than from island to island in the Archipelago. 

 But those slight modifications which tend to bring a species into more exact harmony 

 with surrounding conditions can be accumulated and rendered constant by 'natural 

 selection ' in an island where intercrossing witli the forms of other districts is impos- 

 sible ; while on a continent the same mode of action will be very often neutralized by 

 the intermingling of the various forms which must occasionally come in contact with 

 each other, except where the habits of the animal are much opposed to locomotion. 

 It is an interesting confirmation of this theory that the only species of Pitta which 

 presents any well-marked varieties is that which has the widest range. Two or three 

 forms of P. liCfif/alcnsis [_P. coronata, the sjiecies figured] have been described as 

 distinct species; but it is found that these forms are unstable, and graduate into each 

 other. We have here an evident tendency to j)roduce distinct forms, which inter- 



