a a ee eee 
_I have done so, I am unable to discover. 

Nov. 24, 1870] 
NATURE 
65 

whether germs can retain their v/fality for the same 
lengthened periods ; as he himself says, the proof of the 
theory ought to rest on direct evidence: “ It must be con- 
fessed that the crucial observation has yet to be made ; 
if vegetable germs exist in the drift, they can be discovered 
beforehand. I am not aware that any thorough search 
has ever been made for them.” 


LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his Correspondents. No notice is taken of anonymous 
communications. | 
The Difficulties of Natural Selection 
Mr. Wallace’s ‘* Reply” has disappointed me. From his un- 
rivalled knowledge of the forms of animal life in those countries 
where nature is the most luxuriant, and from the extraordinary in- 
terest with which he invests every subject that he handles, I had 
expected from him something more conclusive than that he 
should charge his opponent with errors which he has not com- 
mitted, and should reply to his arguments by a simple begging 
of the question. 
The first ‘‘ important error” with which Mr. Wallace charges 
me is, that ‘‘I lead my readers to understand that there is 
only one completely mimicking species of Zeféalis.” Where 
I have, it is true, 
adduced one particular and striking instance as a sample of 
the rest, but distinctly say that “in a comparatively small area, 
several distinct instances of such perfect mimicry occur ;’ and 
point out how strongly, in my view, this tells against the theory 
of Natural Selection. In the next paragraph, ‘‘three great 
oversights ” are alleged. Firstly, ‘‘that each Zeftalis produces 
not one only, but perhaps twenty or fifty offspring.” Mr. 
Wallace can hardly have supposed that I imagined each 
butterfly laid only a single egg, like the rok. The argument, 
however, is unaffected. In a species the numbers of which 
do not materially vary from year to year, it is obvious that, 
whatever the number of eggs laid, only one offspring from 
each individual, or rather two from each pair, survive to the 
pericd at which they themselves produceoffspring. The ‘‘second 
oversight” is “that the right variation has, dy the /ypothesis, a 
greater chance of surviving than the rest ; and the third, that at 
each succeeding generation the influence of heredity becomes 
more and more powerful.” By what hypothesis? ‘Ihe hypo- 
thesis that these small variations in the right direction are useful 
to the individual—the very hypothesis against which I am con- 
tending as unproved; as neat a case of Zetitio ¢rincipii as one often 
meets with. My ‘‘ errors” in fact, amount to a non-admission of 
my opponent’s premisses, who then naively adds, ‘‘ with these 
three modifications the weight of the argument is entirely 
destroyed !’’ Of course it is, The ‘‘new factor of which I take 
no actount”? in the next paragraph, is again entirely dependent 
on the admission of the natural selectionist premisses. 
With regard to the distinction between man and other animals, 
I much regret if I have unwittingly misrepresented Mr, Wallace’s 
view ; but if I have done so, I think it is owing to that 
view not having yet been clearly pronounced. Mr. Wallace 
distinctly states his opinion that ‘‘a superior intelligence has 
guided the development of man in a definite direction.” | 
(‘* Contributions,” p. 359. I have Mr. Wallace’s own 
authority for saying that M. Claparede has misinterpreted 
him in referring this superior intelligence to a ‘‘ Force 
supérieure,” a direct action of the Creator; what alternative is 
there left but to suppose that it was man’s own intelligence that 
he had in view? Whenever Mr, Wallace more clearly enunciates 
this portion of his theory, I think there will be no difficulty in 
showing that the same principle, whatever it may be;.is operative 
in the lower creation as well as in man. 
Having disposed, as I think, of Mr. Wallace’s chief points of 
reply, I may be permitted to point out one or two errors into 
which he has himself, itfseems to me, fallen. The changes of 
mimicry are, he says, ‘‘ wholly superficial, and are almost entirely 
confined to colour.” I was certainly surprised to read this, 
recollecting so many instances to the contrary, not only among 
tropical insects, but in the close approximation in form of some | 


of our own Diptera to certain genera of Hymenoptera; and 
recollecting also the numerous illustrations of protective form 
and habit which Mr, Wallace himself gives, not only describing 
| which natural selection may be considered a prime factor. 
| these, I think, I have not misrepresented. 
them but haying also drawn them with such exquisite fidelity, 
(See ‘‘Malayan Archipelago.”) In the Kal/lima paralekta of 
Sumatra, for instance, he says, ‘‘we thus have size, colour, 
form, markings, and habits, all combining together to pro- 
duce a disguise which may be said to be absolutely perfect.” 
(‘‘ Contributions,” p. 61). Another sentence I had to read three 
or four times before I could believe that Mr. Wallace had penned 
it. In objecting to my parallelism between the development of 
protective resemblance and of instinct, he says, ‘in birds mimi- 
cry is very rare, only two or three cases being known.”’ I do not 
know whether Mr. Wallace draws any subtle distinction between 
‘*mimicry ” and ‘* protective resemblance ;” but if so, he should 
have noticed that it is the latter which I speak of as ‘‘ being 
strongly developed in birds.” I had, on reading the above sén- 
tence, to tum again to my ‘‘ Contributions,” to see whether I 
was correct in my impression that we find there the statement 
that ‘‘in the desert the upper plumage of every bird without 
exception is of one uniform isabelline or sand colour;” that 
“the ptarmigan is a fine example of protective colouring” 
(‘* Contributions,” pp. 50, 51), and that two whole chapters aré 
devoted to the wonderful protective instinct of birds in the 
| matter of their nests. 
On one point raised in my parer I am disposed somewhat to 
modify my views, and I do so with the greatest pleastite, in my 
objection, namely, to the title of Mr. Darwin’s gtéat work. Taking 
the origin of sfczes as distinct from the origin of mere varieties, 
there is undoubtedly a sense, as Mr. Wallace points oiit, ih 
The 
law of variation is a centrifugal, the law of natural selection 4 
centripetal force ; the one acting by itself would produce a wild 
chaos, the other a barren uniformity ; equilibrium can only be 
the result of their joint co-operation. 
Whatever may be my “‘ihability to grasp the theory,” I hopé 
I have shown that [ have not falleii into the errors with which 
Mr. Wallace charges me. All the main points of the argument 
seem to me to be left untouched by him. Me has brought for- 
ward no evidence that extremely small variations do afford any 
immunity from the attacks of enemies. He gives no explanation 
of the tendency of the Zef/a/is referred to by Mr. Bates ‘to 
produce naturally varieties of a nature to resemble Zthomtie,” 
He does not attempt to account for the parallelism of the develop- 
ment of protective resemblance aiid of instinct in the animal world. 
He fails to explain the nature of the intelligence which was opera- 
tive in the creation of man, and which isa principle unknown in the 
rest of the organic world. Students of Nattire who have spent 
their lives in their own country must always yield in point of 
experience to those who have had the advantage of comparing 
the faunze and florze of other climates, and can only arrive at their 
conclusions from the facts brought to their notice by travellers ; 
Appeal to authority, 
as authority, is always to be deprecated in Science. I may, how- 
ever, perhaps be permitted to strengthen my position by a quo- 
tation from a work, which I had not read at the time of writing 
my paper, by one who will be acknowledged to have some know- 
ledge of the ways of Nature (Huxley’s Lay Sermons, p. 323) — 
“ After much consideration, and with assurecly no bias against 
Mr. Dartwin’s views, it is our clear conviction that, as the evi- 
dence stands, it is not absolutely proven that a group of animals, 
having all the characters exhibited by a species in Nature, has 
ever been originated by selection, whether artificial or natural.” 
ALFRED W. BENNETL 
Westminster Hospital, Nov. 19 ; Fee 
P.S.—Since writing the above, Mr. Jenner Weir has kindly 
called my attention to two papers read by him before the 
Entomological Society, ‘‘ On the Relation between the Colour and 
the Edibility of Lepidoptera and theit Larve.” In one of these 
I find the following remarkable statement :—‘‘ Insectivorous 
birds, as a general rule, refuse to eat hairy larvee, spinous larve, 
and all thosé whose colours are very gay, and which rarely, or 
only accidentally conceal themselves. On the other hand, they 
eat with great relish all smooth-skinned laivee of a green or dull 
brown colour, which are nearly always nocturnal in their habits 
or mimic the colour or appearance of the plant they frequent.” 
Here at least it would seem as if imferfect mimicry was any- 
thing but beneficial to the individual ; how can the principle 6 
natural selection account for its propagation in these instarices ? 

Tue soul of many an anti-Darwinian will have been cheered by 
Mr. A. W. Bennett's paper on “‘ The Theory of Natural Selection 
from a Mathematical Point of View.” It is, in fact, a very 
