66 
The President's Add^^ess. 
ence_, when tlie Protozoa amongst animals and the Desmi- 
deaceae and Diatomacese amongst plants were scarcely heard 
ofj and when the rudest conceptions prevailed of the nature 
of the tissues of animals and plants. From the time, how- 
ever_, of our countryman Hooke^ and the Dutchman Leewen- 
hoek, there had always been a few observers who worked in 
the faith that one day the minute knowledge they prized 
would become the foundation and keystone of all our know- 
ledge of organic beings. Such were Malpighi, Trembley, 
Ellis^ the two Adamses, Baker, Gleichen, Otto Friedrich 
Miiller, and Vaucher. The philosophy and brilliant teachings 
of Linnseus served for a time to throw a shade over the 
labours and works of these laborious students of nature. It 
was at the beginning of the present century that the genius 
of our great countryman, Robert Brown, gave a new impulse 
to inquiries by the microscope ; who, whilst expounding the 
laws of morphology in the vegetable kingdom, showed that 
the facts on which they depended could not be known but 
by the aid of the microscope. His profound researches were 
committed silently to the great tide of human knowledge, 
and have ever since gone on expanding our views of the na- 
ture and relations of organized beings. It was his researches 
that fixed the attention of Schleiden, who, in his masterly 
essay on ^ Phytogenesis,^ laid the foundation of the cell- 
theory of development, which found in the animal kingdom 
so able an exponent in Schwann. 
On the other hand, Ehrenberg, with a diligence unsurpassed, 
carried his microscope (which he tells us he bought in the 
streets of Berlin for thirty shillings) to all parts of the world, 
for the purpose of observing the microscopic beings that 
inhabited the earth. The result of his labours appeared in 
that magnificent folio dedicated to the description of the 
forms and habits of the Infusory Animalcules. However able 
we may be at this time to criticise the labours of Ehrenberg, 
with our compound achromatics costing more pounds than 
his microscope did shillings, no one can deny the vast 
impetus his researches gave to microscopical research. If 
Brown had led the way to the discovery of the intimate 
workings of the laws of life, it was Ehrenberg who demon- 
strated how vast was the number of forms veiled from the 
naked eye that living beings assumed. 
Whilst these two great observers were working with the 
humblest instruments and demonstrating the superiority of 
mind above all instrumental arrangements, the makers of 
microscopes were not idle. Lenses of great power and accurate 
definition were made by Amici in Modena, Plosl in Vienna, 
