Page - 383 - in The Origin of Species

AFFINITIES OF EXTINCT SPECIES 383 as unequal intervals of time have elapsed between consecM- tive formations. It is no real objection to the truth of the statement that the fauna of each period as a whole is nearly intermediate in character between the preceding and succeeding faunas, that certain genera offer exceptions to the rule. For in- stance, the species of mastodons and elephants, when ar- ranged by Dr. Falconer in two series,—in the first place according to their mutual affinities, and in the second place according to their periods of existence,—do not accord in arrangement. The species extreme in character are not the oldest or the most recent; nor are those which are interme- diate in character, intermediate in age. But supposing for an instant, in this and other such cases, that the record of the first appearance and disappearance of the species was complete, which is far from the case, we have no reason to believe that forms successively produced necessarily endure for corresponding lengths of time. A very ancient form may occasionally have lasted much longer than a form else- where subsequently produced, especially in the case of terres- trial productions inhabiting separated districts. To compare small things with great; if the principal living and extinct races of the domestic pigeon were arranged in serial affinity, this arrangement would not closely accord with the order in time of their production, and even less with the order of their disappearance; for the parent, rock-pigeon still lives; and many varieties between the rock-pigeon and the carrier have become extinct; and carriers which are extreme in the important character of length of back originated earlier than short-beaked tumblers, which are at the opposite end of the series in this respect. Closely connected with the statement, that the organic re- mains from an intermediate formation are in some degree intermediate in character, is the fact, insisted on by all palaeontologists, that fossils from two consecutive formations are far more closely related to each other, than are the fos- sils from two remote formations. Pictet gives as a well- known instance, the general resemblance of the organic re- mains from the several stages of the Chalk formation, though the species arc distinct in each stage. This fact