-
_
PREFACE
iX:
unt, has been the directive principle in dierentiation and
evolution.
Does this theory giVe a'reasonable'explanation
ofthefacts?
*
_'
'
'
‘
The aùthor’s attitude toWards thetheory may be illusÂ
trated by quotations from the writings of Charles Darwin,
“
The theory “of natural:selection implies that aïorm…will
_
remain unaltered unless some alteration beto itstbenet.”
Again,
when we descend
details, we cannot prove: that
,
a
single species has changed, nor can we prove that the
supposed changes are benecial, which is the groundwork
of the theory. Nor-Can we explain why Some species have
changed and others have not.”
,,
'
_
,
.
_
«_
Most biologists of the present day willprobably agree
-
with these words of Darwin.
The theory of Natural
‘5
;
Selection cannot be demonstrated as an interpretation of
Ï'Ï:--,
evolution in the past and We nd ourselves unable to make
use of it in unravelling the sequence of detailed events
which lead up
to the formation of characters in the present.
_
Darwin has also admitted the possibility, that
“
through '_
the nature of the organism and of surrounding conditions,
‘
but not through natural selection,” new groups of animals
have been formed. These statements apply with special
force to the1shes and it is not difcult to point to numerous
"
cases, where Changes havebeen quite the reverse of
cial, ahd yet the species have survived and multiplied.
One of these may be noted here by‘_ way of
,
The Sun—sh when a tiny larvà goes through a c0nd‘ition
which may well be compared to dropsy.
The natural
coùrse of development comes to“ a stop, the ordinary—51
muscles and the nerve cord degenerate, at least do
develop, and the larva rolls about in ”the
'
iike a helpless drop of jelly. But the life is not extihguished
5
'
the form changes again,
,
nerve-connections are established,æd
'
to become one of the largest of shes with a
feeuïtdity greater than anything known
the _.
animal kingdom.»-Ë
of the
îÇ_ :
adult Sun—sh
no