Introduction: Variation. 57 



is well known there; wood-ruff transplanted from the woods loses its aroma. 

 Examples could be added by scores. Though we cannot explain these alterations 

 mechanically, facts remain; so it is with insignificant variations in the colours of 

 birds in new localities, if isolated. How easily colour may be influenced is 

 shown by the following case of one of the Musophagidae, Corythaix albocristatus, first 

 made known by Dr. Chenu (Encyclopedic D'Hist. Nat. Oiseaux 2™" partie 1855 

 p. 55): "Une particularite remarquable, dont nous devons la communication a 

 Jules et Edouard Verreaux, si bons observateurs , c'est que les douze ou 

 quatorze pennes alaires, qui sont d'un si beau pourpre violatre, perdent cette 

 couleur chez les individus vivants, lorsqu'elles ont ete mouillees par la pluie: si, 

 dans cet etat, on vient a les toucher ou a les frotter avec les doigts, ceux-ci se 

 trouvent aussitot rougis par la couleur pourpree qui a deteint sur eux; et, en 

 sechant, ces memes plumes reprennent leur eclat primitif. Sur la depouille de 

 rOiseaux, aucun effect semblable ne se produit. Ce fait nous parait unique 

 dans la classe des Oiseaux."') Though this be exceptional, no doubt chemical 

 or mechanical alterations of colour occur elsewhere, be they dependent on food, 

 light or other external influences, touching which we know next to nothing 

 at present. Alteration of colour in individuals, gone astray to isolated localities, 

 leads us to geographical variation, which should next be treated of. 



2. Geographical Variation. 



Although it is conceivable, and indeed likely, that a new species may 

 sometimes owe its origin to dimorphism, a condition which may be ultimately 

 due to the successful multiplication of a single case of exceptional individual 

 variation, it is nevertheless far more certain that the great majority of the 

 peculiar forms of Celebes and the neighbouring islands are what are termed 

 geographical species or local races, which have developed their distinctive 

 characters while geographically isolated from one another. In the Celebesian 

 area there are about 150 species of this description now known, not to speak 

 of a large number of partially formed races. The latter are in many respects 

 the most interesting, as they show species in the first stages of their differen- 

 tiation, and their study holds out the best hope of solving the problem of the 

 origin of species — or at least of the majority of species. The differences seen 

 are often very small, but of a very palpable description, as, for instance, the 

 broader black border to the secondaries of Eos histrio in Sangi, the narrower 

 border in Talaut; the darker grey of the head of Phoenicophaes calorhynchus in 

 North Celebes, the lighter grey in the South, and so on. These differences 

 may be due to an inherent tendency in the individuals in question to evolve 



•1 Compare Schlegel: J. f. 0. 1858, 381 ; A. Bogdanow: C. R. Ac. So. Paris 18.57 XLV, 311 and 1602 

 LIV, 660; Brehm Tierl. 3. ed. 1891 V, 138; Krukenberg: "Die Parbstoffe der Pedenr' in liis Vergl.- 

 Physiol. Stud. 5. Abt. 1881, 75. 



Meyer & Wiglesworth Biraa of Celebes Ol.ay 5tb, lyiS). g 



