"Even Linnaeus," says Romanes, "was express in his limitations of
true scientific work in natural history to the collecting and
arranging of species of plants and animals." The question, "What is
it?" came first; then, "How did it come to be what it is?" We are
just awakening to the question, "Why this progressive system of
forms, and what does it all mean?"
Let us experiment a little in forming our own classification of a
few vertebrates. We see a bat flying through the air. We mistake it
for a bird. But a glance at it shows that it is a mammal. It is
covered with hair. It has fore and hind legs. Its wings are
membranes stretched between the fingers and along the sides of the
body. It has teeth. It suckles its young. In all these respects it
differs from birds. It differs from mammals only in its wings. But
we remember that flying squirrels have a membrane stretching along
the sides of the body and serving as a parachute, though not as
wings. We naturally consider the wings as a sort of after-thought
superinduced on the mammalian structure. We do not hesitate to call
it a mammal.
The whale makes us more trouble; it certainly looks remarkably like
a fish. But the fin of its tail is horizontal, not vertical. Its
front flippers differ altogether from the corresponding fins of
fish; their bones are the same as those occurring in the forelegs of
mammals, only shorter and more crowded together.
Pages:
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49