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and productive of much good work by many observers, it is to be 
regretted that it has not been more freely used as an aid to micro- 
scopical research. While the last quarter of a century has seen 
much progress in other departments of natural science, compara- 
tively little has been added to our knowledge of the development of 
the many forms of animal and vegetable life with which the aquatic 
kingdom abounds, and two causes exist which may account for this. 
First, microscopists as a rule are too much satisfied with a collection 
of pretty objects for their cabinets, and not sufficiently alive to the 
interest and importance of observing and recording the various 
stages through which those much admired objects attain their ulti- 
mate condition; and secondly, an idea seems prevalent that the 
maintenance of an aquarium in such a state as would conduce to 
the growth and devolopment of microscopic life is a matter of im- 
mense difficulty, and only to be undertaken by a few especially 
gifted individuals. No greater mistake can interpose itself in the 
way of your intellectual enjoyment than this, for the maintenance 
of an aquarium is a much more easily managed affair than the 
keeping of a birdcage, and should offer no obstacle even to a child. 
As I feel, from the questions put to me by members of the Quekett 
Microscopical Club and other friends, that many would willingly 
adopt this means of adding additional observations to those already 
made in this.department of natural history if they could be put in 
the way of aquarium research, I propose this evening to lay before 
you such directions as an experience of ten or twelve years’ suc- 
cessful management of a small marine aquarium may enable me to 
offer towards the attainment of a similar success by any member 
who may feel inclined to take up this particular study. If in carry- 
ing out my proposal I may seem to dwell too much upon details, I 
must crave your indulgence, asking you to believe that they are not 
trivial, and that while their faithful observance will ensure success, 
their negleet will result in failure. The treatment of this subject 
will naturally resolve itself into three divisions—first, the vessel 
employed to hold the water; secondly, the water employed; and 
thirdly, the most suitable oceupants of the aquarium. The vessel 
employed may be anything that will hold water, and at the same 
time keep its natural character unaltered. Successful observations 
have been made in vessels of every size and shape, from earthen 
pans and pie dishes through the entire range of glass jars and 
propagating bell glasses up to the regularly constructed tank, and 
therefore the vessel employed should present no difficulty to those 
who wish to commence this method of microscopical research. In 
these days of amateur ingenuity a tank could be constructed with 
much facility by anyone wishing to possess one, or, if money be no 
object, tanks can be bought ready for the reception of the inhabi- 
tants intended to be observed. These tanks are formed of slate and 
glass—materials which are not affected by sea water. No metal 
