86 Elliot, Inheritance of Acquired Characters. [January 



another group, M. f. riviilaris^ distinguished from its New 

 Mexico and Arizona relatives by darker color and greater size. 

 Northward along the Pacific coast to the Columbian region 

 another style is produced ^M. f. samuelis)^ almost black in its 

 coloration, and the smallest in size of all the subspecies. In the 

 Columbian region a race, M. f. guttata^ occurs, rufescent in 

 hue, and with the bill more slender in porportion than any of 

 the forms already mentioned. The typical home or central 

 region of the dispersion of this form is the Columbia River region 

 coastwise, but before reaching this point changes of an inter- 

 mediate character in the color of plumage among individuals oc- 

 cur, foreshadowing the subspecies that ranges through the coast 

 region of British Columbia, northward to Sitka. Thus migrants 

 obtained in the foil and winter at Nicasio,* near San Francisco, 

 are intermediate in coloration between the Pacific coast subspecies 

 and that of the Columbian region, and individuals from the base 

 of the eastern slope of the Cascades in Oregon exhibit grada- 

 tions from that form which connect it by insensible stages with 

 the subspecies of the Columbian region, M. f. guttata. 



What is to be gathered from this mass of indisputable evidence, 

 save that the variations of this widely dispersed form are caused 

 primarily by the effects of environment, carried on, if you please, 

 by natural selection, but not originated by it. The allied forms 

 change with the localities they frequent. The different kinds 

 of food, aridity, humidity, the elevation and depi-ession of the 

 earth's surface, producing mountain ranges and valleys, of various 

 heights and depths, in short the many and potential physical and 

 climatic influences that constitute what we call environment, 

 have separately or together produced the various forms now ex- 

 isting, and that the characters acquired through these influences 

 liave been transmitted from parent to off'spring. The various 

 forms are isolated in the centre of their dispersion, as if on islands, 

 from their allies, and when two of these are connected in the out- 

 lying portions of their dispersion, where the environment exerts 

 influences derived from both neighboring regions, a new form is 

 prevented from arising by the interbreeding of the two subspecies, 

 even though the environment in the intermediate region could 

 exert, if isolated, sufficient influences to produce and maintain 



*Henshaw, Bull. Nuttall Ornith. Club, 1879, p. 159. 



