Mr. A. R. Wallace on the Genus Pitta. 109 



nearly equally divided between the Indian and Australian zoolo- 

 gical regions. Of the remaining groups, five sections, com- 

 prising nine species, are Indian, while three sections and seven 

 species are Australian. The great majority of the species, how- 

 ever, inhabit the Malayan Islands, as distinguished from the 

 continent of Asia on the one hand and Australia on the other. 

 Thus we find in 



Africa and Asia . . 6 species of 3 groups, 

 Australia .... 2 „ 2 „ 

 Malay Islands ... 25 „ 8 „ 

 proving that the genus is preeminently Malayan, and is one of 

 the very few which characterize the Archipelago as a whole, and 

 not, as is much more frequently the case, the eastern or western 

 portion of it only. 



The island which contains the greatest number of species is 

 Borneo, which would thus seem to be the metropolis of the 

 group. It possesses five or perhaps six species ; Sumatra and 

 the Malay Peninsula each have five; the Philippines possess 

 two ; and Java only one. These islands combined, constituting 

 what I term the Indo-Malayan province,have thus fourteen species 

 of Pitta. Further east, no one island possesses more than two 

 species, due partly to the much smaller size of the islands, and 

 also because in the great island of New Guinea we reach the 

 eastern limit of the genus. On combining these islands to form 

 the Austro-Malayan province, only ten species of Pitta are found 

 to inhabit it. The variety of form also, as expressed by the 

 number of sections into which the species fall, is greater in the 

 Indian than in the Australian division of the Archipelago. Thus, 



Austro-Malayan province . 10 species of 4 groups. 

 Indo-Malayan province . . 14 „ 6 „ 



It is interesting to remark that two species of the same group 

 scarcely ever inhabit one island : where two or more species arc 

 found in an island, they almost invariably belong to as many 

 distinct sections of the genus. This illustrates Mr. Darwin's 

 theory of the extermination of closely allied forms by the more 

 dominant race, and also of the efi"ects of intercrossing in keep- 

 ing up the uniformity of a species over a wide area. It thus 



