Origin of Species Variorum

→ though in these cases the modification has been greater in degree, and has taken a longer time to complete? 1859 1860 1861

though in these cases the modification has been much greater in degree, and has taken a longer time to complete? 1866

all under the so-called natural system? 1869 1872

→ have to make out 1859 1860 1861 1866 1869

are forced to trace 1872

→ as far as we can judge, 1859 1860 1861 1866 1869

OMIT 1872

But it may be asked, what ought we to do, if it could be proved that one species of kangaroo had been produced, by a long course of modification, from a bear? Ought we to rank this one species with bears, and what should we do with the other species? The supposition is of course preposterous; and I might answer by the argumentum ad hominem , and ask what should be done if a perfect kangaroo were seen to come out of the womb of a bear? According to all analogy, it would be ranked with bears; but then assuredly all the other species of the kangaroo family would have to be classed under the bear genus. The whole case is preposterous; for where there has been close descent in common, there will certainly be close resemblance or affinity.

As descent has universally been used in classing together the individuals of the same species, though the males and females and larvæ are sometimes extremely different; and as it has been used in classing varieties which have undergone a certain, and sometimes a considerable amount of modification, may not this same element of descent have been unconsciously used in grouping species under genera, and genera under higher groups, →though in these cases the modification has been greater in degree, and has taken a longer time to complete? I believe it has

~~thus~~

thus

been unconsciously used; and

thus only

only thus

can I understand the several rules and guides which have been followed by our best systematists.

As we

have no written

pedigrees,

pedigrees;

we →have to make out community of descent by resemblances of any kind. Therefore we choose those characters

which

which,

→as far as we can judge, are the least likely to have been

modified,

modified

in relation to the conditions of life to which each species has been recently exposed. Rudimentary structures on this view are as good as, or even sometimes better than, other parts of the organisation. We