The sun. [volume] (New York [N.Y.]) 1833-1916, 1892-06-05

1877.
enormous change In the conditions as regards
the possibility Of any other such species being
| subsequently evolved. As Sir Charles Lyell has
put IL. two rational species can mover CO. exist
| on the globe.
Another and opposite objection to the theory
OF natural selection has sometimes been put
| forward. viz, that We ought never to find In.
ferior forms Of organization in company with
| superior. because In struggle for existence
the latter ought to have exterminated the
former. According to the most recent express
sion Of this view. in every locality thore
would only be one species. and that the m ost
highly organized: and thus a few superior
races would partition the earth among them.
to the entire seclusion OF the innumerabe va
rieties. species. genera, and orders which now
inhabit It," To this statement Mr.. Romanes
deems 1t sufficient to reply by the coun-
ter inquiry On what would these few SUI
premely organized species subsistp In
exterminnting others on the exhaustive
scale supposed. they would thems selves be
quickly and very literally improved of the
face OF the earth. Even whom the statement Is
not made in so extravaRant form. It is pro.
nounced futile as an objection. unless it has
first been shown that we know exactly oil the
conditions OF tho complex struggle for exits
tence between the higher and lower forms in
question. This 1t is impossible for us to know.
The mere fact that one form has been
changed in virtue OF this struggle, must in
many cases Of itself determine a change in the
conditions OF the struggle. Again, the other
and closely allied forms (which furnish the best
grounds for the obiection) may also have under
gone defensive changes. although these may be
less conspicuous to our observation. or per-
haps less suggestive OF Improvement" to our
imperfect means OF Judging. Lastly. there is
the broad fact that the objection applies only
to those cases where for some reason or an.
other the lower forms have not been exposed
to struggle Of fatal intensity. But We know
that In millions Of other cases the lower Il. e.,
less fitted forms have succumbed. That
there is. indeed. general tendency for lower
forms to Yield their places to higher is shown
by tho gradual advance Of organization
throughout geological time: for II all the in
ferior forms had survived. the earth could not
have contained them unless she had been con.
tinually growing into something like the size
OF Jupiter.
Hitherto Mr. Romanes has been considering
criticisms which have arisen from misappre-
tensions OF Darwin's theory. He goes on to
examine an objection admitted to be logically
sound. which. nevertheless. is futile. be-
cause 1t is not supported by fact. This obiec-
ton. which Is made by Mr.. st. George Mivart,
Is that similar organs. or structures. are to be
met with in widely different branches Of the
tree OF life. 1t Is conceded by Mr.. Romanes
that this would be an objection fatal to the
theory OF natural selection. supposing these
organs. or structures. in the cases compared.
TO be not merely analogous, but also
homoloeous. 1t would be- he admits. incredi-
Bile that in two totally different lines OF de-
scent one and tho same structure should have
been built up independently by two parallel |
series OF variations. and that In these two |
lines OF descent Ii should always. and indepen-
IDENTIFY have ministered to the same function. |
On the other hand. there would be nothing |
against the theory OF natural selection in the |
fact that two structures not homologous, |
should come by independent variation in two |
different lines OF descent. to be adapted to per-
form the same function. For 1t belongs to the |
very essence OF the theory of natural selection
that useful function should be secured by
favorable variations OF whatever structural
may happen to be presented by Diff
lerent organic types. Flying for instance. is a
very useful function. and it has been developed
Independently In at least four different lines of
the insects. reptiles. birds,
ind mammals. Now. II in all. or indeed In
my. OF these four cases the wings had been de-
'eloped on the same anatomical pattern. SO as
1ot only to present the analoecul res emblance
which they must present In order to discharge
heir common function OF flying. but likewise
IN homoloeous or structural resemblance
showing that they had been formed on the
zane anatomical plan: il such a case could be
PRODUCED. 1t is acknowledged BY Mr. Romanes
hat the theory Of natural selection would DO
Upset. Now. Mr.. Mivart has alleged that there
IRE several such cases In organic nature, |
De has instanced the eye Of the cuttlef1sh |
ID not only analogous. but also homologous |
With the eye OF q true fish-that is to say, the
we OF a mollusk with the eye OF a vertebrate
md he has also instanced the remark able re-
emblance OF a shrew to a mouse. or. in other
yords OF ar tnsectivorous mammal to
odent. Both OF these examples are examined
n this volume and pronounced cases not OF
lomologous but OF analogous. similarity
That to say. the points Of likeness have not
zen produced on the same anatomical plan |
Even the author of this book encounters q
'reat difficulty IN explaining. by the theory Of
atural selection. the preservation OF the first
beginnings OF structures which are then use
ess. though afterward. when more fully de-
elopeu. they become useful. How. for in
lance. are we to account on the Darwinian |
ypothesis for the existence Of the electric or
an In the tail OF the skater Where electric
rgans OCCUR In the gymnotus and torpedo
hey are obviously useful for both offensive
nd defensive purposes. because they produce
,ore or less powerful shocks. On the other
and. tho discharge from the electric
ryan in the tail OF skate is ap-
arently useless. for it is too week to be
slt by the hand. and its existence can only
o demonstrated by the telephone. Yet for the
elivery of such an impotent discharge. i'm
erceptibe alike to prey and to enemies. there
provided IN organ Of such extreme peculi-
rity and complexity that. regarded as q piece
living mn nhaniera L