| → will 1859 1860 1861 |
| and they will 1866 1869 1872 |
|
| → vertebrate 1859 1860 1861 |
| and then less differentiated vertebrate 1866 |
| and at that time less differentiated vertebrate 1869 1872 |
|
| → as in that of 1859 1860 1861 1866 |
| as with 1869 |
| for instance 1872 |
|
|
a common
together with their retention by inheritance of some characters in common, we can understand the excessively complex and radiating affinities by which all the members of the same family or higher group are connected together. For the common
of a whole
now broken up by extinction into distinct groups and sub-groups, will have transmitted some of its characters, modified in various ways and degrees, to
the
→will
consequently be related to each other by circuitous lines of affinity of various lengths (as may be seen in the diagram so often referred to), mounting up through many predecessors. As it is difficult to show the blood-relationship between the numerous kindred of any ancient and noble
even by the aid of a genealogical tree, and almost impossible to do
without this aid, we can understand the
difficulty which naturalists have experienced in describing, without the aid of a diagram, the various affinities which they perceive between the many living and extinct members of the same great natural class. |
|
| Extinction, as we have seen in the fourth chapter, has played an important part in defining and widening the intervals between the several groups in each class. We may thus account
for the distinctness of whole classes from each other— for instance, of birds from all other vertebrate animals— by the belief that many ancient forms of life have been utterly lost, through which the early progenitors of birds were formerly connected with the early progenitors of the other
→vertebrate
classes. There has been
extinction of the forms of life which once connected fishes with batrachians. There has been still less
some
classes,
→as in that of
the Crustacea, for here the most
diverse forms are still
|
