426 
NATURE 
the kingdom of God. But neither can it issue in any discovery 
which contradicts the existence of that kingdom ; nor can any 
mind in the light of the kingdom of God hesitate to conclude 
that if such seeming contradictions arise there is implied the 
presence of error either as to the facts or as to conclusions from 
the facts.” These are valuable words and weighty testimonies. 
But in a matter of this importance one must not forbear to point 
out what may seem to be wanting even in the dicta of such men 
as the two Ihave quoted. Neither of them have allowed the 
possibility of error attaching itself to the utterances of more 
than one of the two parties in such issues as those contemplated. 
Neither appears to have thought of the cases in which religious 
men, if not theologians, have brought war on the world because 
of the offences they have with ill-considered enunciations created. 
And, whilst fully sympathising with all that the Archbishop and 
Mr. Campbell have said, I must say that they appear to me to 
have left something unsaid, and this something may be wrapped 
up in the caution that there may be faults on both sides. But 
at any rate this Section cannot be considered a fit place for the 
correction of errors save of the physical kind ; and all other 
considerations are for this week and in this place extraneous. In 
some other week or in some other place it will be, if it has not 
already been, our duty to give them our best attention. 
To come now to the kind of considerations which are the 
proper business of Section TD, let me say that for the discussion 
of the question of Spontaneous Generation very refined means of 
observation, and, besides these, very refined means of experi- 
mentation, are necessary. And I shall act in the spirit of the 
advice I have already alluded to as given to the world by one of 
her greatest teachers, if I put before you a simple but a yet un- 
decided question for the solution of which analogous means of a 
far less delicate character would appear to be, but as yet have not 
proved themselves to be, sufficient. Thus shall we come to see 
very plainly some of the bearings, and a few of the difficulties, of 
the more difficult of the two questions. What an uneducated 
person might acquiesee in hearing spoken of as Spontaneous 
Generation, takes place very constantly under our very eyes, when 
a plot of ground which has for many years, or even generations, 
been devoted to carrying some particular vegetable growth, 
whether grass or trees, has that particular growth removed from 
it. When sucha clearing is effected, we often see a rich or even 
a rank vegetation of a kind previously not growing on the spot 
spring up upon it. The like phenomenon is often to be noted on 
other surfaces newly exposed, as in railway cuttings and other 
escarpments, and along the beds of canals or streams, which are 
laid bare by the turning of the water out of its channel. Fumi- 
tory, rocket, knotgrass, cowgrass, Polygonum aviculare, and 
other such weeds, must often have been noted by every one of us 
here in England as coming into and occupying such recently dis- 
turbed territories in force ; whilst in America the destruction of a 
forest of one kind of wood, such as the oak or the chestnut, have 
often been observed to be followed by an upgrowth of young 
forest trees of quite another kind, such as the white pine, albeit 
no such tree had been seen for generations growing near enough 
to the spot to make the transport of its seeds to the spot seem a 
likely thing. In one case referred to by Mr. Marsh, the hickory, 
Carya porcena, a kind of walnut, was remarked as succeeding a 
displaced and destroyed plantation of the white pine. Now the 
advocates of Spontaneous Generation must not suspect me of 
hinting that there is any question, except in the minds of the 
grossly ignorant, of the operation of any such agency as spon- 
taneous generation here; no one would suggest that the seeds of the 
Polygonum aviculare, to say nothing of those of the Hickory, were 
produced spontaneously ; but what I do say is, that the question 
of how those seeds came there is just the very analogue of the 
one which they and their opponents have to deal with. And it 
is not definitely settled at this very moment. Let us glance at 
the instructive historical parallel it offers. For the very gross 
and palpable facts of which I have just spoken there are two ex- 
planations offered in works of considerable authority. The one 
which has perhaps the greatest currency and commands the 
largest amount of acceptance is the one which, in the words of 
De Candolle, regards da couche de terre végétale d’un pays comme 
un magazin de graines, and supposes that in hot summers and 
autumns, such as the present, the fissures in the ground, which 
have proved so fatal this year to the young partridges, swallow up 
a multitude of seeds, which are restored again to life when the 
deep strata into which they are thus introduced, and in which 
they are sealed up as the chasms close up, come in any way to be 
laid open to the unimpeded action of the sun and moisture. 
Squirrels, again, and some birds resembling herein the rodent 
mammalia, bury seeds and forget to dig them up again ; and it is 
supposed that they may bury them so deep as to be protected 
from the two physical agencies just mentioned. Now Germina- 
tion cannot take place in the absence of oxygen, and I would 
add that well-sinkers know to their cost how often the super- 
ficial strata of the earth are surcharged with carbonic acid. The 
rival explanation and the less popular—I do not say the less 
scientific—looks to the agency of transportation as occurring 
constantly, and sufficing to explain the facts. By accepting this 
explanation, we save ourselyes from running counter to certain 
experiments, some of which were carried out, if I mistake not, 
under the auspices of this Section (see British Assoc. Reports), 
and which appear to curtail considerably the time during which 
seeds retain their vitality, and to multiply considerably the number 
of conditions which must be in force to allow of such retention 
for periods far shorter than those which have to be accounted for. 
A better instance of the expediency of checking the interpretations 
based merely upon observations however accurately made by 
putting into action experiments, cannot be furnished than by 
recording the fact put on record by Mr. Bentham, when discuss- 
ing this question in his last year’s address to the Linnaxan Society. 
“* Hitherto direct observation has, as far as I am aware, only 
produced negative results, of which a strong instance has been 
communicated tome by Dr. Hooker. In deepening the lake in 
Kew Gardens, they uncovered the bed of an old piece of water, 
upon which there came up a plentiful crop of 7y/A2, a plant not 
observed in the immediate vicinity ; and it was therefore con- 
cluded that the seed must have been in the soil. To try the 
question, Dr. Hooker had six Ward’s cases filled with some of 
the soil remaining uncovered close to that which had produced 
the Zypha, and carefully watched ; but not a single 7yp/a came 
up in any one of them.” (Note in President’s address May 24th, 
1869, page 72 of Linnzean Society’s Proceedings. ) 
To this I would add that experiments wich a positive result, 
and that positive result in favour of the second hypothesis, if 
hypothesis it can be called, are being constantly tried in our 
colonies for us, and on alarge scale. I had taken and written 
here of the Zolygonum aviculare, the ‘‘knot” or ‘‘cowgrass”’— 
having learnt on the authority of Dr. Hooker and Mr. Travers 
(see Natural History Review, January 1864, p. 124, Oct. 
1864, p. 619), that it abounds in New Zealand, along the road- 
side, just as it does in England—as a glaring instance, and one 
which would illustrate the real value of the second explanation 
even to an unscientific man and to an unassisted eye. But on 
Saturday last I received by post one of those evidences which 
make an Englishman prond in thinking that whithersoever ships 
can-float thither shall the English language, English manners, 
and English Science be carried, in the shape of the second volume 
of the Transactions of the New {Zealand Institute, full like the 
first, from beginning to the last page with thoroughly good matter. 
In that volume, having looked at its table of contents, I turned 
to a paper by Mr. T. Kirk on the Naturalized Plants of New 
Zealand, and in this, at p. 142, I find that Mr. T. Kirk prefers 
to regard the Polygonum aviculare of New Zealand as indigenous 
in New Zealand. Hence that illustration which would have 
been a good one falls from my hands. And I must in fairness 
add, that because one agency is proved to be a vera causa, it is 
not thereby proved that no other can by any possibility be com- 
petent simultaneously to produce the same effect, whatever the 
Schoolmen with the law of Parsimony ringing in their ears 
may have said to the contrary. Ihave dwelt upon this subject 
at this length with the purpose of showing how much difficulty 
may beset the settlement of even a comparatively simple question 
which involves only the use of the unassisted eye, or at most of a 
simple lens. The @ fortiori argument, I leave you to draw for 
yourselves with the simple remark, that the question of 
Spontaneous Generation is now at least one to be decided by the 
microscope, and by the employment of its highest powers in 
alliance with other apparatus of all but equal complexity. 
We come, in the second place, to saya word as to the extent of 
the influence which organic and living particles, of microscopic 
minuteness but solid for all that, have been supposed, and in 
some instances at least have been proved, to exercise upon the 
genesis and genesiology of disease, and so upon the fortunes of 
our race, and our means for bettering our condition, and that of 
our fellows. I need not refer to Dr. Sanderson’s valuable Report 
(just published in the Privy Council’s Medical Officer’s Blue 
Book, Twelfth Report, 1870, p. 229, upon those contagion particles 
which he proposes to call by the convenient name, slightly modi- 
cilia 
[ Sep¢. 22, 1870 
