Chap. X. 
AFFINITIES OF EXTINCT SPECIES. 
335 
corresponding lengths of time: a very ancient form 
might occasionally last much longer than a form else¬ 
where 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 as well as they could be in serial afiSnity, this 
arrangement would not closely accord with the order in 
time of their production, and still less with the order of 
their disappearance; for the parent rock-pigeon now 
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 beak 
originated earlier than short-beaked tumblers, which are 
at the opposite end of the series in this same respect. 
Closely connected with the statement, that the or¬ 
ganic 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 related to 
each other, than are the fossils from two remote forma¬ 
tions. Pictet gives as a well-known instance, the 
general resemblance of the organic remains from the 
several stages of the Chalk formation, though the species 
are distinct in each stage. This fact alone, from its 
generality, seems to have shaken Professor Pictet in his 
firm belief in the immutability of species. He who is 
acquainted with the distribution of existing species over 
the globe, will not attempt to account for the close 
resemblance of the distinct species in closely consecutive 
formations, by the physical conditions of the ancient 
areas having remained nearly the same. Let it be 
remembered that the forms of life, at least those in¬ 
habiting the sea, have changed almost simultaneously 
throughout the world, and therefore under the most 
different climates and conditions. Consider the pro- 
