Origin of Species Variorum

→ a 1859 1860 1861 1866 1869

for many generations a 1872

→ breed for many generations— 1859 1860 1861

breed for many generations — 1866 1869

breed— 1872

→ very small proportion 1859 1860 1861 1866 1869

remnant 1872

→ some 1859 1860 1861 1866

removed by some 1869 1872

croup,

loins,

rump,

a bar at the end of the tail, with the outer feathers externally edged near their bases with white. As all these marks are characteristic of the parent

rock- pigeon,

rock-pigeon,

I presume that no one will doubt that this is a case of reversion, and not of a new yet analogous variation appearing in the several breeds. We

may,

may

think,

think

confidently come to this conclusion, because, as we have seen, these coloured marks are eminently liable to appear in the crossed offspring of two distinct and differently coloured breeds; and in this case there is nothing in the external conditions of life to cause the reappearance of the

slat-blue,

slaty-blue,

with the several marks, beyond the influence of the mere act of crossing on the laws of inheritance.

No doubt it is a very surprising fact that characters should

re-appear

reappear

after having been lost for many,

probably

perhaps

for hundreds of generations. But when a breed has been crossed only once by some other breed, the offspring occasionally show →a tendency to revert in character to the foreign →breed for many generations— some say, for a dozen or even a score of generations. After twelve generations, the proportion of blood, to use a common expression,

from

of any

one ancestor, is only 1 in 2048; and yet, as we see, it is generally believed that a tendency to reversion is retained by this →very small proportion of foreign blood. In a breed which has not been crossed, but in which both parents have lost some character which their progenitor possessed, the tendency, whether strong or weak, to reproduce the lost character

might,

might

~~be,~~

be,

as was formerly remarked, for all that we can see to the contrary,

be transmitted

transmitted

for almost any number of generations. When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that

one individual

the offspring

suddenly takes after an ancestor →some hundred

gene- rations

generations,

generations