400 
NATURE 
[ Sept. 15, 1870 
teropoda.”—W. C. Williamson, ‘On the Organisation and | After careful search through the ‘‘ Exercitationes de Genera- 
Affinities of the Calamities of the Coal Measures.”—G. A. 
Laborn, ‘‘On the Tertiary Coal-field of Southern Chili.”— 
Charles Ricketts, ‘‘On a Railway Section across the Prescot 
€oal-field.”—John W, Judd, ‘‘On the Age of the Wealden.” — 
Geo. Busk, a paper by Dr. Leith Adams, *‘ Ona New Species of 
Fossil Elephants from Malta.” —Charles Jeaks, ‘“On the Norwich 
Grag.” 
ADDRESS OF THOMAS HENRY HUXLEY, LL.D., F.R.S., 
PRESIDENT, 
My Lorns, LADIES, AND GENTLEMEN,—It has long been 
the custom for the newly installed President of the British Asso- 
ciation tor the Advancement of Science to take advantage of the 
elevation of the position in which the suffrages of his colleagues 
had, for the time, placed him, and, casting his eyes around the 
horizon of the scientific world, to report to them what could be 
seen from his watch-tower ; in what directions the multitudinous 
divisions of the noble army of the improvers of natural know- 
ledge were marching ; what important strongholds of the great 
enemy of us all, ignorance, had been recently captured ; and, 
also, with due impartiality, to mark where the advanced posts 
of science had been driven in, or a long-continued siege had 
made no progress. : ; 
I propose to endeavour to follow this ancient precedent, in a 
manner suited to the limitations of my knowledge and of my 
capacity. I shall not presume to attempt a panoramic survey of 
the world of science, nor even to give a sketch of what is doing 
in the one great province of biology, with some portions of 
which my ordinary occupations render me familiar. But I shall 
endeavour to put before you the history of the rise and progress 
of asingle biological doctrine ; and I shall try to give some 
notion of the fruits, both intellectual and practical, which we 
owe, directly or indirectly, to the working out, by seven gene- 
rations of patient and laborious investigators, of the thought which 
arose, more than two centuries ago, in the mind of a sagacious 
and observant Italian naturalist. 
It is a matter of every-day experience that it is difficult to 
prevent many articles of food from becoming covered with 
mould ; that fruit, sound enough to all appearance, often con- 
tains grubs at the core ; that meat, left to itself in the air, is apt 
to putrefy aud swarm with maggots. Even ordinary water, if 
allowed to stand in an open vessel, sooner or later becomes 
turbid and full of living matter. 
The philosophers of antiquity, interrogated as to the cause of 
these phenomena, were provided with a ready and a plausible 
answer. It did not enter their minds even to doubt that these 
low forms of life were generated in the matters in which they 
made their appearance. Lucretius, who had drunk deeper of 
the scientific spirit than any poet of ancient or modern times 
except Gocthe, intends to speak as a philosopher, rather than as 
a poet, when he writes that ‘‘with good reason the earth has 
gotten the name of mother, since all things are produced out of 
the earth. And many living creatures, even now, spring out of 
the earth, taking form by the rains and the heat of the sun.” * 
The axiom of ancient science, ‘‘that the corruption of one 
thing is the birth of another,” had its popular embodiment in 
the notion that a seed dies before the young plant springs from 
it ; a belief so wide spread and so fixed, that Saint Paul appeals 
to it in one of the most splendid outbursts of his fervid 
eloquence :— 
“Thou fool, that which thou sowest is not quickened, except 
it die.” + 
The proposition that life may, and does, proceed from that 
which has no life, then, was held alike by the philosophers, the 
poets, and the people, of the most enlightened nations, eighteen 
hundred years ago ; and it remained the accepted doctrine of 
learned and unlearned Europe, through the middle ages, down 
even to the seventeenth century. 
It is commonly counted among the many merits of our great 
countryman, Harvey, that he was the first to declare the oppo- 
sition of fact to venerable authority in this, as in other matters ; 
but I can discover no justification for this wide-spread notion. 
* Tt is thus that Mr. Munro renders 
‘* Linquitur, ut merito maternum nomen adepta 
Terra sit, € terra quoniam sunt cuncta creata. 
Multaque nunc etiam exsistant animalia terns 
Imbribus et calido solis concreta vapore.” 
De Rerum Natura, lib. v. 793-796. 
But would not the meaning of the last line be better rendered “‘ Deve- 
loped in rain-water and in the warm vapours raised by the sun”? 
+ 1 Corinthians xv. 36. z ; age 
L qe cla nei primi giorni del mondo pradusse per comande 
tione,” the most that appears clear to me is, that Harvey believed 
all animals and plants to spring from what he terms a ‘‘prinvor=. 
dium vegetale,” a phrase which may nowadays be rendered ‘‘a 
vegetative germ ;” and this, he says, is ‘‘ ovd/orme,” or ‘*egg- 
like;” not. he is careful to add, that it necessarily has the shape 
of an egg, but because it has the constitution and nature of one. 
That this ‘‘Arimordium oviforme” must needs, in all cases, 
proceed from a living parent is nowhere expressly maintained by 
Harvey, though suchan opinion may be thougit to be implied 
in one or two passages; while, on the other hand, he does, more 
than once, use language which is consistent only witha full belief 
in spontaneous or equivocal generation.* In fact, the main 
concern of Harvey’s wonderful little treatise is not with gene- 
ration, in the physiological sense, at all, but with development ; 
and his great object is the establishment of the doctrine of epi- 
genesis. : 
The first distinct enunciation of the hypothesis that all living 
matter has sprung from pre-existing living matter, cdme ftom 4 
contemporary, though a junior, of Harvey, a native of that 
country, fertile in men great in all departments of human activity, 
which was to intellecttial Europe, in the sixteenth and seven- 
teenth centuries, What Germany is in the nineteenth. It was in 
Italy, and from Italian teachers, that Harvey received the most 
important part of his scientific education. And it was a student 
trained in thesame schools, Francesco Redi —a man of the widest 
knowledge and most yersatile abilities, distinguished alike ag 
scholar, poet, physician, and natttralist who, just two hundred 
and two years-ago, ptblished his ‘* Esperienze intorno alla Gene- 
razione degl’ Insetti,” and gave to the world the idea, the growth 
of which it is my purpose to trace. Redi’s book went through 
five editions in twenty years; and the extteme simplicity of his 
experiments, and the clearness of his arguments, gained for his 
views, and for their consequences, almost universal acceptance. 
Redi did not trouble himself much with speculative considera- 
tions, but attacked particular cases of what was supposed to be 
‘*spontaneous generation” experimentally. Here are dead 
animals, or pieces of meat, says he ; I expose them to the air in 
hot weather, and in a few days they swarm with maggots. You 
tell me that these are generated in the dead flesh ; but if I put 
similar bodies, while quite fresh, into a jar, and tie some fine 
gauze over the top of the jar, not a maggot makes its appearance, 
while the dead substances, nevertheless, putrefy just in the sate 
way as before. It is obvious, therefore, that the maggots aré 
not generated by the corruption of the meat ; and that the cattse 
of their formation must be a something which is kept away by 
gauze. But gauze will not keep away aériform bodies, or fluids. 
This something must, therefore, exist in the form of solid par- 
ticles too big to get through the gauze. Nor is one long left in 
doubt what these solid particles are ; for the blowflies, attracted 
by the odour of the meat, swarm round the vessel, and, urged by 
a powerful but in this case misleading instinct, Jay eggs out of 
which maggots are immediately hatched upon the gauze. The 
conclusion, therefore, is unavoidable; the maggots are not 
generated by the meat, but the eggs which give rise to them are 
brought through the air by the flies. : 
These experiments seem almost childishly simple, and one 
wonders how it was that no one ever thought of them before, 
Simple as they are, however, they are worthy of the most careful 
study, for every piece of experimental work since done, in regard 
to this subject, has been shaped upon the model furnished by the 
Italian philosopher. As the results of his experiments were the 
same, however varied the nature of the materials he used. it is 
not wonderful that there arose in Redi’s mind a presumption, 
that in all such cases of the seeming production of life from dead 
matter, the real explanation was the introduction of living germs 
from without into that dead matter.+ And thus the hypothesis 
* See the following passage in Exercitatio I. :—‘‘Item sfonte nascenticg 
dicuntur; non quod ex futredine oriunda sint, sed quod casu, natura, 
sponte, et zquiyocd (ut aiunt) generatione, a parentibus syi dissimilibus 
proveniant.” Again, in ‘‘De Uteri Membranis”:—‘*In cunctorum viven- 
tium generatione (sicut diximus) hoc solemne est, ut ortum ducunt a Arimor- 
dio aliquo, quod tum materiam tum efficiendi potestatem in se habet : sitque 
adeo id, ex quo et a quo quicquid nascitur, ortum suum ducat. Tale prim- 
ordium in animalibus (sive ad alits generantibus proveniant, sive sponte, aut 
ex putredine nascentur) est humor in tunica aliqua aut putamme conclusus.” 
Compare also what Redi hes to,say respecting Harvey's opinions, “ Esperi- 
enze,” p. II. r 
+ “Pure contentandomi sempre in questa ed in ciascuna altro cosa, da 
ciascuno pit, sayio, 1a dove io difettuosamente parlassi, esser corretto ; non 
tacero, che per molte osservazioni molti volti da me fatte, mi sento inclinaio. 
a cxeshere che Ja terra, da quelle prime piante, e da quei primi avimali in poi, 
ento de! sovrang, 
4 
