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THP TROPICAL AGRICULTURIST. [J UNE 2 . lS 9°. 
mon nomenclature, and for simultaneous observations 
in widely separated localities. International Confe- 
rences are the order of the day, and the new units 
which they have defined are based upon experiments 
by many first-rate observers in many lands, amongst 
whom the name of Lord KayleigU stands second 
to none. 
On the side of chemistry the periodic law Of Mende- 
leeff has become established as a generalization of the 
first importance, and the extraordinary feat of fore- 
telling the physioal properties of an as yet undiscovered 
element has attracted to it the attention of the whole 
scientific world. 
The onoe permanent gases are permanent no more. 
Duong and Petit's law has found a complement in the 
methods of Rauolt. The old doctrine of valency is giv- 
ing way to more elastic hypotheses. The extraordin- 
ary progress of organic chemistry, which originated in 
the work and influence of Liebig end the Giessen 
school, has continued at an aoceterated rate. The prac- 
tical value of even the most recondite investigations of 
pure science has again been exemplified by the enor- 
mous development of the ooal-tar industry, and by 
the numerous syntheses of organic products which have 
added to the material resources of the community. 
The increase of our knowledge of the sun by means of 
localized spectroscopic observation ; the application of 
photography to astronomy, and more recently still the 
extension and generalization of the nebular hypothesis 
are perhaps the most remarkable developments of those 
branohes of soience which relate to astronomy. Stars 
which no human eye will ever see are now known to 
us as surely as those whioh are clearly visible. The 
efforts to reduca nebulae, comets, and stars under one 
common law, as various cases of the collision or aggre- 
gation of meteoritic swarms, and the striking investi- 
gations of Prof. Darwin on the effects of tidal action, 
and on the application of the laws of gases to a meteo- 
ritic plenum, give promise of a fuller knowledge of the 
birth and death of worlds. 
In the biological soienoes, the progress during the 
last twenty years has consisted ohiefly in the firm esta- 
blishment of the Darwinian doetriu ,:, and the applica- 
tion of it and its subordinate conceptions in a variety 
of fields of investigation. The progress of experimental 
physiology has been marked by increasing exaotitude 
in the application of physical methods to the study of 
the properties of living bodies, but it has not as yet 
benefited, as have other branches of biology, from the 
fecundating influence of Darwin's writings : hence there 
is no very prominent physiological discovery to be 
reoorded. The generation of scientific men which is 
now coming to middle age has been brought up in 
familiarity with Mr. Darwin's teaching, and is not 
affected by anything like hostility or a priori anta- 
gonism to suoh views. The result is seen in the vast 
number of embryological researches (stimulated by 
the theory that the development of the individual 
is an epitome of the development of the race) which 
these twenty years have produoed and in the daily 
increasing attention to that study of the organism as 
a living thing definitely related to its conditions whioh 
Darwin himself set on foot. The marine laboratories 
of Naples, Newport, Beaufort, and Plymouth, have 
come into existence (as in earlier years their fore- 
runners on the coast of France), and served to organize 
and facilitate the study of living plants and animals. 
The Ohallenger and other deep-sea exploring expedi- 
tions have sailed forth and returned with their booty, 
which has been described with a detail and precision 
unknown in former times. The precise methods of 
microscopic study by means of section-outtiug — due 
originally to Strieker, of Vienna — have within these 
twenty yeata made the study of cell-structure and 
cell-activity as essential a part of morphology as it had 
already become of physiology. These, and the frank 
adoption of the theory of desoent, have swept away 
old ideas of classification and affinities, and have rele- 
gated the AsoiAian " polyps " of old days to the group 
of Vertebrata, and the Sponges to the Ocelenterates. 
The nuoleus of the protoplasmio cell — which twenty 
years ago had fallen from the high position of impor- 
tance aooorded to it by Schwann — has, through the 
reaearchea of Butschli, Flemming, and Van Beneden 
been reinstated, and is now shown to be the seat 
of all-important activities in connection with cell-divi- 
sion and the fertilization of the egg. The discovery, 
of the phenomena of karyokinesis and their relation to 
fertilization will be reckoned hereafter as one of the 
most, if not the most, important of the biological dis- 
coveries of the past twenty years. 
Apart from Darwinism, the most remarkable deve- 
lopment of biological studies during these " twice ten- 
tedious year " is undoubtedly the sudden rise and 
gigantic progress of our knowledge of the Bacteria. 
Though the foundations were laid fifty years ago by 
Sohwann and Henle, and great advances were made 
by Pasteur and by Lister just before our period, yet 
it is within this span that the microsoope and precise 
methods of culture have been applied tj the study of 
the " vibrions," or " microbes," and the so-called " bac- 
teriology" established. We now kno.v, through the 
labours of Toussaint, Ohauveau, Pasteur, and Koch, 
of a number of diseases which are definitely caused by 
Bacteria. We also have learnt from Pasteur how to 
control the attack of some of these dangerous para- 
sites. Within these twenty years the antiseptio sur- 
gery founded by Sir Joseph Lister has receivd its full 
measure of trial and confirmation, whilst bis oppor- 
tunities and those of his fellow-countrymen for making 
further discoveries of a like kind have been ignoraatly. 
destroyed by an Act of Parliament. 
To particularize some of the more striking zoological 
discoveries which oome within our twenty years, we 
may cite — the Dipnooua fish-like oreature Oeratodus of 
the Queensland rivers, discovered by Krefftjthe jum-- 
ping wheel-animalcule Pedalion, of Hudson ; the deve- 
lopment and the anatomy of the archaic Arthropod 
Peripatus worked out by Moseley, Balfour, and Sedg- 
wiok ; the Hydrocorallinse of Moseley, an entirely new 
group of compound animals ; the fresh-water jelly-fish 
Limnocodium of the Regent's Park lily-tank ; the Silu- 
rian scorpion of Gotland and Lanarkshire ; the proto- 
zoon Chlamydomyxa discovered by Archer in the Irish 
bogs; the Odontornithes and the Diuooerata of the 
American palaeontologists ; the intracellular digestion 
obtaining in animals higher than Protozoa, and the 
significance of the " diapedesis " of blood-ccrpuscles 
in inflammation, and the general theory of phagocytes 
due to Mecznikow ; the establishment of the principle 
of degeneration as of equal generality with that of 
progressive development, by Anton Dohrn ; the demon- 
stration by Weismann and others that we have no 
right to mix our Darwinism with Lamarckism, since 
no one has been able to bring forward a single case of 
transmission of acquired characters. Perhaps the 
attempt to purify the Darwinian doctrine from La- 
marckian assumption will hereafter be regarded— 
whether it be successful or not — as the most charac- 
teristic feature of biological movement at the end of 
our double decade. Its earlier portion was distin- 
guished by the publication of some of Darwin's later 
works. Its greatest event was his death. 
In botany, twenty years ago, the teaching in our Uni- 
versities was practically sterile. In one of our earliest 
numbers, Prof. James Stewart defended with some 
vigour the propriety of intrusting botany to a lecturer- 
at Cambridge who was also charged with the duty of 
leoturingon electricity and magnetism. It is startling: 
to oompare a past, in which botany was regarded as a 
subject which might be tacked on anywhere, with ita 
present condition, in which there is scarcely a seat of 
learning in the three kingdoms whioh is not turning out 
serious work. The younger English school would be 
ungrateful if it did not acknowledge its debt to the 
eminent German teachers from whom it has derived 
so much in the tradition and method of investigation. 
Sachs and De Bary have left an indelible mark on our 
younger Professors. But it would be a mistake to 
suppose that English modern botany has simply derived 
from Germany. It has developed a oharaoter of its 
own, in which the indireot influence of Darwin's later 
work oan be not indistinotly traced. There has been a 
gradual revolt in England, the ultimate consequences of 
which have still to be developed, against the too physi- 
cal conception of the phenomena of plant life whioh 
has been prevalent on the Continent. Darwin, by hie 
researches on insectivorous plants and plant movement 
