Chap. XXIII. CONDITIONS OF LIFE. 287 



We may, also, infer the prepotent influence of the constitution of the 

 organism over the definite action of the conditions of life, from the several 

 cases given in the earlier chapters of parallel series of varieties,— an im- 

 portant subject, hereafter to be more fully discussed. Sub-varieties of 

 the several kinds of wheat, gourds, peaches, and other plants, and to a 

 certain limited extent sub-varieties of the fowl, pigeon, and dog, have been 

 shown either to resemble or to differ from each other in a closely corre- 

 sponding and parallel manner. In other cases, a variety of one species 

 resembles a distinct species ; or the varieties of two distinct species resemble 

 each other. Although these parallel resemblances no doubt often result from 

 reversion to the former characters of a common progenitor ; yet in other 

 cases, when new characters first appear, the resemblance must be attributed 

 to the inheritance of a similar constitution, and consequently to a tendency 

 to vary in the same manner. We see something of a similar kind in the 

 same monstrosity appearing and reappearing many times in the same animal, 

 and, as Dr. Maxwell Masters has remarked to me, in the same plant. 



We may at least conclude thus far, that the amount of modi- 

 fication which animals and plants have undergone under domes- 

 tication, does not correspond with the degree to which they 

 have been subjected to changed circumstances. As we know 

 the parentage of domesticated birds far better than of most 

 quadrupeds, we will glance through the list. The pigeon has 

 varied in Europe more than almost any other bird ; yet it is a 

 native species, and lias not been exposed to any extraordinary 

 change of conditions. The fowl has varied equally, or almost 

 equally, with the pigeon, and is a native of the hot jungles of 

 India. Neither the peacock, a native of the same country, nor 

 the guinea-fowl, an inhabitant of the dry deserts of Africa has 

 varied at all, or only in colour. The turkey, from Mexico, has 

 varied but little. The duck, on the other hand, a native of 

 Europe, has yielded some well-marked races ; and as this is an 

 aquatic bird, it must have been subjected to a far more serious 

 change in its habits than the pigeon or even the fowl which 

 nevertheless have varied in a much higher degree. The goose 

 a native of Europe and aquatic like the duck, has varied less 

 than any other domesticated bird, except the peacock. 



Bud-variation is, also, important under our present point of 

 view. In some few cases, as when all the eyes or bads on the 

 same tuber of the potato, or all the fruit on the same plum- 

 tree, or all the flowers on the same plant, have suddenly- 

 varied in the same manner, it might be argued that the varia- 



