On the other hand, I see no good reason for doubting the necessary
alternative, that all these varied species have been evolved from
pre-existing crocodilian forms, by the operation of causes as completely
a part of the common order of nature, as those which have effected the
changes of the inorganic world.
Few will venture to affirm that the reasoning which applies to
crocodiles loses its force among other animals, or among plants. If one
series of species has come into existence by the operation of natural
causes, it seems folly to deny that all may have arisen in the same way.
A small beginning has led us to a great ending. If I were to put the bit
of chalk with which we started into the hot but obscure flame of burning
hydrogen, it would presently shine like the sun. It seems to me that
this physical metamorphosis is no false image of what has been
the result of our subjecting it to a jet of fervent, though nowise
brilliant, thought to-night. It has become luminous, and its clear rays,
penetrating the abyss of the remote past, have brought within our ken
some stages of the evolution of the earth. And in the shifting "without
haste, but without rest"[75] of the land and sea, as in the endless
variation of the forms assumed by living beings, we have observed
nothing but the natural product of the forces originally possessed by
the substance of the universe.
Pages:
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127