Oct. 7, 1886] 
OUR BOOK SHELF 
La Terre des Merveilles. Par Jules Leclercq. 
Librairie Hachette et Cie., 1886.) 
IN this volume M. Jules Leclercq describes a visit made 
by him a few years ago to the Yellowstone National Park, 
during which he saw all the sights of this terre des 
mervetlles. The writer is already well known in his own 
country as an accomplished writer of popular books of 
travel, and accordingly he makes the most of the Yellow- 
stone region and its wonders. His sketches of these are 
preceded by a very interesting chapter on the early ex- 
plorations of the territory, from the visits of the first 
adventurous trappers. There are two maps—one a 
detailed map of the “ Park,” the other a general map of 
part of the United States to show the position of the 
Yellowstone region. There is also a considerable number 
of illustrations. The volume is published in Hachette’s 
“Collection des Voyages illustrés,” and is a clever, well- 
written popular account of a district full of natural 
wonders. 
(Paris: 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake to 
return, or to correspond with the writers of, rejected manu- 
scripts. No notice is taken of anonymous communications. 
[The Editor urgently requests correspondents to keep their letters 
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that it ts impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts.] 
The Cereals of Prehistoric Times 
My friend Mr. Carruthers in the interesting address delivered 
recently to Section D of the British Association, makes a remark 
which I confess surprises me. He says (NATURE, September 9, 
P- 453) :—‘‘ It is remarkable that in our own country, with all 
the appliances of scientific cultivation and scientific farming, we 
have not been able to appreciably surpass the grains which were 
harvested by our rude ancestors of 2000 years ago.” He men- 
tions in support of this conclusion that ‘‘ the wheat from lake- 
dwellings in Switzerland for which I am indebted to Mr. J. T. 
Lee, F.G.S., are fair samples.” 
This is certainly a striking fact. The persistence of specific 
and even of varietal types in a country like Egypt is 
what we might expect, because the very preservation of the 
material evidence is a proof that the physical conditions have 
persisted likewise. But that cultivated plants have remained 
unaltered since the Stone Age seems a conclusion difficult to 
accept in the face of every-day experience as to what can be 
done in modifying them. The data collected by Prof. A. De 
Candolle (‘‘L’Origine des Plantes cultivées,” pp. 284, 285) 
leads me, I think, to the conclusion that Mr. Lee’s specimen 
must be exceptional. Prof. De Candolle mentions three varieties 
of wheat as cultivated in the Stone Age; of these he says :— 
** Aucune n’est identique avec les blés cultivés de nos jours. 
On leur a substitué des formes plus avantageuses.”’ Two of these 
have been obtained from lacustrine dwellings. He remarks that 
the most ancient lacustrine people of Western Switzerland culti- 
vated a wheat with small grains, which Heer has carefully 
described and figured under the name of Zyiticum vulgare 
antiguorum. These people he regards as contemporaries of the 
Trojan war, if not older. The culture of this kind of wheat 
persisted in Switzerland till the Roman conquest. Unger found 
the same form in a brick of the pyramid of Dahschir in Egypt 
of the date B.c. 3359. The other variety (Zyiticum vulgare 
compositum muticum, Heer) was less common in Switzerland in 
the first age of stone, but is the one most frequently found in 
the less ancient lake-dwellings of Western Switzerland and 
Italy. W. T. THISELTON DYER 
Physiological Selection and the Origin of Species 
HAVING written for the Fortnightly Review a full reply 
to Mr. Wallace’s article in that journal, I will not here antici- 
pate what I have there to say. But, seeing that he has 
repeated in these pages the substance of his criticism, I 
NATURE 
545 
will here also repeat the substance of my reply. On the 
present occasion, therefore, it is enough to remark that I have 
never made the ‘‘ extraordinary statement that, during his whole 
life, Mr. Darwin was mistaken in supposing his theory to be a 
theory of the origin of species.” On the contrary, as I shall 
hereafter show, so far as this matter is concerned, both my 
opinions and my statement of them are in full agreement with 
those presented in Mr. Darwin’s works. 
Without wishing to discuss with Mr. Francis Darwin the 
meaning of the sentence which he quoted from the ‘‘ Origin of 
Species,” I feel it is only due to my own understanding to give 
the following explanation. If any one will turn to the sentence 
in question (p. 247, 6th ed.), he will find that it constitutes an 
integral part of an argument showing that sterility between 
species cannot have been brought about by natural selection. 
The argument is that, even supposing sterility with parent forms 
to be an advantage, it is an advantage which could not be 
seized upon by natural selection, and hence that some other 
explanation of such sterility must be found. Now, so 
far as I can see, there is here not only no shadow of 
the theory of physiological selection, but the whole argu- 
ment is proceeding on totally different lines. For the very 
essence of this theory is that the sterility in question seed 
not be supposed to be an advantage, and therefore that any 
variation in the way of such sterility does not require to be 
selected through the struggle for existence, being of its own 
nature a variation which survives. Inno part of Mr. Darwin’s 
writings can I find even the most distant allusion to the possi- 
bility of this particular variation being thus a variation saz 
generis—itself a cause of specific differentiation, and, as such, 
independent of natural selection. Least of all can I find evi- 
dence of any such allusion in the pasage referred to, seeing that 
the argument here consists in expressly regarding the variation 
of sterility as resembling variations in general, and therefore in 
not regarding it as possibly presenting the highly peculiar quality 
of being survivable Zev se. And, considering how fully Mr. 
Darwin has given his reasons for rejecting many ideas much less 
feasible, I confess it appears to me a most extraordinary and 
unaccountable thing that he should nowhere have so much as men- 
tioned this alternative, had it ever been familiar to his mind. I 
may add that, if any reasonable ground can be shown for sup- 
posing this to have been tbe case, it would cause me to abandon 
the whole research. 
Mr, J. H. A. Jenner’s remark cannot apply to the particular 
kind of variation with which alone my theory is concerned, be- 
cause, if so, it would amount to saying that the more sterile the 
variety is with its parent form the more will this sterility be 
increased by intercrossing with that form, which is absurd. But 
with regard to many other kinds of :demefictal variation the 
remark of course is true. 
Iam greatly obliged to Mr. Evershed for directing my atten- 
tion to Mr. Catchpool’s letter in NATURE (vol. xxxi. p. 4). 
Having obtained a copy of the issue referred to, I find, as he 
says, that ‘‘the theory of physiological selection is very clearly 
put forward.” Moreover, the difficulties against the theory of 
natural selection on account of inutility and sterility are very 
clearly stated. I may take this opportunity of requesting any 
of your readers who may know of any previous publications of 
the theory—no matter how vague or sketchy—to be kind enough 
to furnish references. GEORGE J. ROMANES 
Geanies, Ross-shire, September 18 
Cooke’s ‘‘Chemical Physics” 
IN your issue of September 2 (p. 405) I find under the cover of 
a review of Cooke’s ‘‘ Chemical Physics” that Prof. Armstrong 
has been good enough to quote a passage from my ‘‘ Lessons in 
Elementary Chemistry,” though without naming the source, 
concerning Avogadro’s law, about which he asks the question, 
“*Could anything be more misleading and inaccurate?” My 
friend appears to be no exception to the well-known rule as to 
critics failing to read the books they review, for a note on the 
same page (55) disposes of the ‘‘ inaccuracy,” whilst the ‘‘ mis- 
leading” statement is explained further on (p. 154). On the 
other hand, Dr. Armstrong has not followed the usual practice 
of critics, who, not being authors, escape from the danger of a 
retort courteous from those whom they find fault with ; and hence 
I feel sure he will forgive me in saying that, whilst fully agreeing 
with him in the statement that a knowledge of mathematics is 
advisable for a chemist if he is to understand physics and physical 
