; CHeMicAL News,
53 British Association.—T he President's Address. { fii

shan is at my disposal to give any detailed account of
them ; but they are of such immense importance in their
:ommercial, social, and sanitary relations that they ought
1ever to be lost sight of,
It is now proved beyond doubt that the origin of putre-«action
 and fermentation is dependent on the presence in
the substances which are the seat of change in these
processes, or in the surrounding air, of the germs of minute
organisms of an animal or vegetable nature, and that the
maintenance of the chemical changes in which these processes
 mainly consist is coincident with and casually (if
not essentially) dependent upon the growth and multiplication
 of these organisms.
Professor Lister had the merit of being the first to apply
:he germ theory of putrefaction to explain the formation
of putrid matters in the living body ; and he has founded
on this theory the now well-known antiseptic treatment
of wounds, the importance of which it would be difficult
'0 over estimate.
The success or failure of plans for the preservation of
meat and other articles of food without question depends
on the possibility of the complete exclusion of the germs
which are the cause of putrefa@tion and fermentation ; and
:heir management must therefore be founded on the most
accurate knowledge of these organisms, and the circumstances
 influencing the persistence of their vitality and
she vigour of their growth.
The theory of Biogenesis has also lately been the guide
in the investigation of the causes of various forms of
disease, both in the lower animals and in man, with the
result of showing that in many of them the infective substance
 consists, in all probability, of germs of minute aninal
 or vegetable organisms.
There is very great probability, indeed, that all the Zynotic
 diseases (by which we understand the various forms
of fevers) have a similar origin. As has been well remarked
 by Baxter in an able paper on ** The Action of
Disinfectants,” the analogies of action of contagia are
similar to those of septic organisms, not to processes
imply of oxidation or dcexidation. These organisms,
studied in suitable finids, multiply indefinitely when intoduced
 in all but infinitesimal proportions, Thus they
we. as pear as we can perceive, the very essence ol
~ontagvia.®*

Leaving, however, these and many other general questions
 regarding the origin of the lowest forms of animal
and vegetable life, let us now turn our attention to the
mode of development of a new being in those belonging
to the higher groups. The general nature of the forma.
tive process, in all instances where fertilised germs are
produced, will be best understood by a short sketch of the
phenomena ascertained to occur in different kinds of
plants.
In the higher or phanerogamic plants it is generally
well known that the combination of two parts of the flower
< necessary to the production of a seed containing the
smbryo or young plant. Beginning with the discovery of
the pollen-tubes by Amici in 1823, the careful and minute
investigations of a long line of illustrious vegetable phywalogists
 have brought to light the details of the process
tw which fertilisation is effected, and have shown, in fa@,
Low the minute tube developed from the inner membrane of
ine pollen-granule, as soon as it falls upon the stigmatic
~sue of the seed-bearing plant, insinuates itself by a rapid
process of development between the cells of the style, and
caches at last the ovule, in the interior of which is the
*mbryo-sac ; how, having passed into the micropyle or
iihce of the ovule, it makes its way to the embryo-sac;
iow a minute portion of the fertilising substance of the
"villa transudes from the pollen-tube into the cavity of
he embryo-sac, in which by this time a certain portion of

* For the most interesting information on this suhje@ I cannot do
etter than refer to the very able Reports by Dr. Burdon Sanderson
nthe" Reports of the Medical Officer of the Privy Council,” 1873.
474. and 189s

the protoplasm has become differentiated into the germina?
vesicle—thereby stimulating it to further growth and de"
relopment, the earliest phenomena of which manifest
‘hemselves by the formation of an investing cell-wall, and
by the occurrence of cell-division, which results in the
formation of the embryo or plantule of the seed.
Thus it appears that the essential part of the process of
production in phanerogamic plants is the formation in the
parent plant of cells of two different kinds, which by themselves
 have little or no independent power of further
growth, but which, by their union, give rise to a produc
n which the power of development is raised to the highest
legree.
“By further researches it is now known that the same
aw prevails in all the remaining members of the vegetable
<ingdom, with the exception only of the very simplest
‘orms.*
In viewing the reprodu@ive process in the series of
Cryptogamic plants, two fads at once strike us as renarkable
 in the modifications which are observed to
iccompany the formation of a productive geria, viz. :—
“first, that the difference between the two produ@ive elements
 becomes as it were more prominent, or more highly
specialised, in the Cryptogamic than in the Phanerogamic
olants ; and, second, that in the simpler and lower forms
his difference gradually disappears till it is lost in com-2lete
 uniformity of the produétive elements,
Thus in the whole tribe of the Ferns and Vascular
Cryptogams, in the higher Alge and Fungi, in the
Characez and in the Mosses, the differentiation of the
aroductive elements is carried to a very high degree ; for
vhile that belonging to the embryo or germ presents the
structure of a simple cell which remains at rest, or in a
:omparatively passive state, and, absorbing into itself the
substance of the other, becomes the seat of subsequent
levelopment, the other, corresponding to the pollen of the
itaminiferous phancrogam, is usually separated from the
>lace of its formation, and, having undergone a peculiar
nodification of structure by which it acquires a@ive moving
tilia, it changes place and is dire@ed towards the germinal
structure, and, coming in contact with its elementary cell,
s more or less absorbed or lost in the fertilising process.
Che protoplasm of the germinal cell thus acted on and feriilised
 then proceeds to undergo the changes of developnent
 by which the foundation is laid for the new plant.
In the Algz and Fungi, however, there are gradations
of the differentiation of the two reproductive cells which
are of the greatest interest in leading to a comprehension
of the general nature of the formative process. For in
he lower and simpler forms of these plants, such as
he Desmidieze, Mesocarpez, and other Conjugataz, we
ind that there is no distinction in stru@ure or form to be
rerceived between the two cells which unite or undergo
:onjugation; and a complete fusion or intermixture of the
wo masses of protoplasm results in the production of a
ingle, usually spherical, mass holding the place of an
:mbryo. And that there is an absence of specialisation
etween the two uniting cells is clearly shown, in both
Jesmidium and Mesocarpus, by the fa@ that the embryo
or zygospore is formed in the mass resulting from the
inion of the protruded portions of the two cells; and in
wore ordinary cases, as in Spirogyra, where the embryo
s formed in one of the two cells, it seems to be indifferent
n which of them it is formed.
From this, which may be regarded as the most elemenary
 type of new produ&ion by the union of the two cells,
‘he transition is not a great one to the development of a
wogeny without any such union. We might conjecture,
‘hen, that the capacity for separate or individual existence
:xtends in the lowest organisms to the whole or to each
structural element of their organisation, while as we rise
n the scale of vegetable life (and the same view might
wply to the animal kingdom) this capacity is more and

* It will be observed that I leave entirely out of view the whole
wubje€t of the multiplication of plants by budding or simple division -