SUB-SPECIES AND THE FIELD NATURALIST. 523 



The need for trinomialism is brought home to tis in India very 

 plainly by the study of our two most common birds, the House- 

 Crow (Corvus insolens), and the Bulbul {Molpastes luemorrhoiis'). 

 Thus the common House-Crow is divided by Blanford and Gates 

 into two species, Corvus splendens in India, and Corvus insolens in 

 Burma. But if we study the forms in various areas, we find that 

 there are still two geographical races which differ even more from 

 the typical Indian bird than does the Burmese one. These two 

 races are the small very dark bird from Cevlon and another from 

 Sind which has the paler plumage so light that it appears almost 

 white. If one merely had tj^pical specimens of the Ceylon bird 

 (Corvus splendens protegatus) and the Sind bird (C s. ziuimeyeri ) 

 to examine, one would at once say here are two excellent species 

 of Crow very different from one another. When, however one 

 has a series from all over India and Burma, it is easy to see that 

 all are one and the same species, but that the dry, glittering plains 

 of Sind have affected the plumage, until the pale brown has been 

 bleached almost white, whereas in Ceylon and Burma the constant 

 humid heat has deepened it until the whole bird is practically 

 black. As regards the Bulbuls, the authors quoted have been 

 very generous in the number of species allowed, and we find 

 Molpastes liamorrlwus, the common Madras red-vented Bulbul, 

 mascjuerading as a good species in no less than six areas, i.e., 

 Ceylon and the greater part of Continental India, (hcrmorrhous), 

 Punjab and N.-W India (imiermedius), Bengal, Assam, and N. E. 

 India, (beniialensis'), Manipur and W. Burma (burmanictis), Kachin 

 Hills, Shan States and N. E. Burma, (cttricapillus), and finally 

 S. E. Burma, and Tennasserim, {nviripiletis). 



But these are nothing but geographical races of one and the 

 same bird, each race grading into the next. Thus, between any 

 two adjoining races within certain areas surrounding each special- 

 ised ai'ea, there is some form of bird not stable, but varying 

 individually in degree, which is neither one race nor the other, 

 but half-way between the two. 



Hume, one of the greatest ornithologists, who combined in him- 

 self ecjually the attributes of the Field and the Museum Naturalist, 

 long ago nearlji grasped the question of geographical races and 

 sub-species. For instance, dealing with the species of Crow- 

 Pheasant, he divided this into several species, shewing the differ- 

 ences between the races with great accurac}-, but eventually, 

 finding that though the extremes varied, they all ran into one 

 another, he once more lumped them under one name. At the 

 same time he definitely laid down the fact that here we had one 

 and the same species of bird with various different races in 

 diff'erent geographical areas. 

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