628 ANNUAL, EEPORT SMITHSONIAN INSTITUTION, 1908. 



are found in nearly all parts of India, and fall into two species, the 

 brown-backed {Thamnohia camljaieiisis) and the black-backed Indian 

 robin {Thamnohia fulicata). The former occurs only in northern 

 India, and the latter is confined to the southern portion of the penin- 

 sula. The hen of each species is a sandy-brown bird with a patch 

 of brick-red feathers under the tail, so that we can not tell by merely 

 looking at a hen to which of the two species she belongs. The cock 

 of the South Indian form is, in winter, a glossy black bird, with a 

 white bar in the wing and the characteristic red patch under the tail. 

 The cock of the northern species, as his name implies, has a sandy- 

 brown back, which contrasts strongly with the glossy black of his 

 head, neck, and underparts. In summer the cocks of the two species 

 grow more like one another, owing to the wearing away of the outer 

 edges of their feathers; but it is always possible to distinguish be- 

 tween them at a glance. The two species meet at about the latitude 

 of Bombay. Oates states that in a certain zone, from Ahmednagar 

 to the mouth of the Godaveri Valley, both species occur, and they do 

 not appear to interbreed. 



It seems impossible to maintain that natural selection, acting on 

 minute variations, has brought about the divergence between these 

 two species. Even if it be asserted that the difference in the color of 

 the feathers of the back of the two cocks is in some way correlated 

 with adaptability to their particular environment, how are we to ex- 

 plain the fact that in a certain zone both species flourish? 



BULBULS. 



A similar phenomenon is furnished by the red-vented bulbuls. This 

 genus falls into several species, each corresponding to a definite lo- 

 cality and differing only in details from the allied species, as, for 

 example, the distance down the neck to which the black of the head 

 extends. There is a Punjab red- vented bulbul {MoVpastes interme- 

 dins)^ a Bengal {Molpastes hengalends) , a Burmese {Molpastes hur- 

 77ianiGus), and a Madras {Molpastes h/rmorrhous) species. 



It does not seem possible to maintain the contention that these 

 various species are the products of natural selection, for that would 

 mean if the black of the head of the Punjab species extended farther 

 into the neck the bird could not live in that part of the country. 

 As there seems to be some intercrossing between these so-called species 

 at places, such as Lucknow, where they meet, I am inclined to regard 

 them as local races of a species, rather than as species of a genus. 

 This, however, does not affect the difficulty which they present to 

 Wallace and his school. 



It is tempting to believe that these slight external differences are in 

 some way or other produced by the direct action of the climate to 



