NATURE, 
oh _ as \ ol ae oe > 
283 
in which this sense appears to be present. 
believed to occur in members of at least two orders of Insects, 
viz. white ants and bees, but I am not aware that any authentic 
cases have been recorded. Horses and cats seem to possess it 
_ in a high degree, and sheep must either have wonderful memo- 
ries, or owe their return, in numerous cases, to the faculty in 
question. Still more wonderful, if we deny them this faculty, 
must be the memory of migratory birds, some of which return, 
_ after months of absence and over thousands of miles, to the same 
nests in successive seasons. If we allow them this faculty it is 
not, from analogy, improbable that migratory mammals and even 
fishes are likewise endowed with it. The most conspicuous 
example, however, is perhaps that afforded by carrier pigeons. 
To take one case: two or three years ago some of these birds 
were flown from the Crystal Palace to Brussels, and it stands, if 
I remember correctly, upon the authority of Mr. Tegetmeier, that 
_ they arrived within a few minutes of a telegram despatched from 
_ the Palace at the moment they were liberated. Now, in this 
case, even the extravagant supposition sometimes made that 
carrier pigeons are guided by the sight of their destination is ex- 
cluded, for, as these birds are not high-flyers, the curvature of 
the earth between London and Brussels would prevent them 
from seeing the latter. And, even if we imagine that these par- 
ticular pigeons occasionally towered to obviate this difficulty, yet 
the curvature of the intervening clouds would have imposed 
another quite as effectual. 
There is still one important point which has not been noticed 
during the discussion of this subject. We possess indications 
that this sense of direction, like other mental capacities, admits 
of cultivation by exercise, and, indeed, that it may remain 
altogether latent and useless until thus developed. If these 
indications represent generalities we have at once an adequate 
explanation of the apparently capricious manner in which this 
faculty occurs.* As this communication is already too long, I 
shall here be brief. 
It is, I believe, a recognised doctrine among fanciers that 
carrier pigeons, however purely bred, must be educated by 
flying short distances before they can be depended upon for long 
ones. Iremember having myself lost a valuable bird by flying 
him, for the first time, at a distance of 500 yards from his nest. 
Although in full view of it he became utterly confused, taking 
long flights in various directions, and ultimately went straight 
out to sea, 
Here is an analogous case in a mammal :—I kept a terrier, of 
highly intelligent parentage, enclosed in a yard with high walls 
from the time of its birth until it was eighteen months old, and 
then took it out for the first time, along the sea-shore. The ex- 
periment elicited several facts of psychological interest, and one 
of them has bearing upon the present subject. Part of the coast 
over which we went and returned was rough with large shingle, 
and the terrier’s locomotive power being very limited, it was unable, 
on the homeward journey, to keep up with my pace. Desiring to 
see what it would do if left alone, I continued for half a mile, 
and waited to see it come up. As it did not doso, I returned, 
and found that the animal had actually reversed its direction and 
gone fully a quarter of a mile from the place where I had left it. 
After having been taken out short distances seven or eight times, 
it was inadvertently lost in a neighbouring wood. Now, it had 
only been in the wood once before, yet its appreciation of direc- 
tion had made so great an advance that it returned an hour after- 
wards. As this terrier never evinced any disposition to track 
footsteps, I do not think its return was due to scent. Anyhow, 
in a few weeks it became an inveterate wanderer, roaming over 
the country far and wide. GEORGE J. ROMANES 
Dunskaith, Ross-shire, July 7 
Comte on the Survival of the Fittest 
Mr. JEvons called attention some time ago to the desirability 
of preparing a list of past thinkers and writers who have held, in 
strength or weakness, the doctrines of Darwin and Spencer. 
Mr. Darwin has himself named a few of those authors, and Prof. 
Haeckel has extended the number. Recent communications in 
NatuRE show that the list is as yet incomplete. In reading 
Comte’s ‘‘Cours de Philosophie Positive” a few years ago, I 
was impressed with the general similarity of certain doctrines 
therein stated with some of Darwin’s theories. Referring re- 
_* In connection with these points compare the suggestive remarks of Mr. 
Darwin, contained in the two concluding paragraphs of his article on Instinct 
(Natourz, vol, vii, p. 418). 
- 
It is popularly 
cently to the 42nd lesson of that course (t. iii.) —‘ Considerations 
générales sur la philosophie biotaxique,” I find that Comte, in 
reviewing the Lamarck-Cuvier controversy, says :— 
‘* Toute la célébre argumentation de Lamarck reposait finale. 
ment sur la combinaison générale de ces deux principes incon- 
testable, mais jusquici trop mal circonscrits: 1°, l’aptitude 
essentielle d’un organisme quelconque, et surtout d’un or- 
ganisme animal, a se modifier conformément aux circon- 
stances extérieures ott il est placé, et qui sollicitent l’exer- 
cise predominant de tel organe spécial, correspondant a telle 
faculte devenue plus nécessaire ; 2°, la tendance, non moins cer- 
taine, 4 fixer dans les races, par la seule transmission hérédi- 
taire, les modifications d’abord directes et individuelles, de 
manicre 4 les augmenter graduellement 4 chaque génération 
nouvelle, si ’action du milieu ambiant persévére identiquement. 
On congoit sans peine, en effet, que, si cette double propricté 
pouvait étre admise d’une manicre rigoureusement indéfinie, tous 
les organismes pourraient étre envisagés comme ayant étre, a la 
longue, successivement produits les uns par les autres, du moins 
en disposant de la nature, de l’intensité, et de Ja durée des influ- 
ences extérieures avec cette prodigalite illimitée qui en cotitant 
aucun effort 4 la naive imagination de Lamarck.” (1st ed. 
**Cours de Philosophie Positive,” t. iii. pp. 560 and 561.) 
Modification and heredity are here strongly asserted, and the 
conditions of unlimited transformation as strongly sketched. In 
continuance of the same argument, Comte, on p. 563, objects to 
Lamarck’s hypothesis, of ,;which he thought very highly as a 
logical effort :— 
““Qu’il repose, ce me semble, sur une notion profondément 
erronée de la nature générale de l’organisme vivant. Sans doute, 
chaque organisme determiné est en relation nécessaire avec une 
systeme egalement déterminé de circonstances extérieures, comme 
je ’ai établi dans la quaranti¢me legon. Mais il n’en résulte 
nullement que la premicre de ces deux forces co-relatives ait di 
étre produite par la seconde, pas plus qu’elle n’a pu Ja produire : 
il s’agit seulement d’un ¢quilibre mutuel entre deux puissances 
hétérogénes et indépendantes. Si l’on congoit que tous les orga- 
nismes possibles soient successivement placés, pendant un temps 
convenable, dans tous les milieux imaginables, la plupart de ces 
organismes finiront, de toute nécessite, par disparaitre, pour ne 
laisser subsister, que ceux qui pouvaient satisfaire aux lois géné- 
rales de cet équilibre fondemental: c'est probablenient d’aprés 
une suite a’éliminations analogues que Vharmonie biologique a 
dd séablir peu a peu sur notre planite, o% nous la voyons 
encore, en effet, se modifier sans cesse d'une maniére semblable. 
Or, la notion d’un tel équilibre général deviendrait inintelligible 
et méme contradictoire, si l’organisme était supposé modifiable 
4 Vinfini sous l’influence supréme du milieu ambiant, sans avoir 
aucune impulsion propre et indestructible.” 
The struggle for existence and the survival of the fittest or 
natural selection are here acknowledged. What is more, the 
fact that the eliminations due to unfitness for the environment or 
medium have produced and is producing biological harmony, is 
pointed out. I have not met with any passages outside of the 
writings of the new school, which are more explicit than these, 
though it must not be understood that their author was a trans- 
formationist. ‘The preface to the volume in which this occurs is 
dated ‘‘ Paris, le 24 Février, 1838.” In his general table ap- 
pended to the sixth volume of his work, Comte says that the 
Lecon from which these extracts are taken was written between 
the 9th and 15th of August, 1836. J. D. BELL 
New York 
The Glacial Period 
CAN you inform me if anyone has suggested the following 
explanation of the existence of the glacial, period? And is the 
explanation I am about to offer a possible one? I put the ques- 
tion in all diffidence, for I have not carefully studied the theory 
of heat : you must therefore regard any utterance of mine cn 
the subject as merely ‘‘a random arrow from the brain.” ‘Well, 
then, it seems to me that the quantity of heat given out in a 
unit of time from a unit of surface of an intensely heated globe, 
such as the sun, does not follow the law of radiation of bodies 
moderately heated. What I mean is this:—It is quite possible 
that at a time when the sun’s mean temperature was higher than 
it is now, his rate of radiation might have been less ; the “quantity 
of heat emitted by him in a unit of time less than it is now. 
For since his chromosphere must have been thicker, and his solid 
or fluid nucleus somewhat less in diameter, I suppose that the 
radiation of the nucleus must have been more retarded by the 
. 
