312 THE ORIGIN OF SPECIES 



between the successive formations. Subject to these allowances, 

 the fauna of each geological period undoubtedly is intermediate in 

 character, between the preceding and succeeding faunas. I need 

 give only one instance, namely, the manner in which the fossils 

 of the Devonian system, when this system was first discovered, 

 were at once recognized by palaeontologists as intermediate in 

 character between those of tie overlying carboniferous and under- 

 lying Silurian systems. But each fauna is not necessarily exactly 

 intermediate, as unequal intervals of time have elapsed between 

 consecutive 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 char- 

 acter between the preceding and succeeding faunas, that certain 

 genera offer exceptions to the rule. For instance, the species of 

 mastodons and elephants, when arranged 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 inter- 

 mediate 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 elsewhere subsequently produced, especially 

 in the case of terrestrial 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 disap- 

 pearance; for the parent rock-pigeon still lives; and many vari- 

 eties between the rock-pigeon and the carrier have become extinct; 

 and carriers which are extreme in the important character of 

 length of beak 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 remains 

 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 re- 

 lated to each other, than are the fossils from two remote forma- 

 tions. Pictet gives as a well-known instance, the general resem- 

 blance of the organic remains from the several stages of the 



