15 
the double purpose of aérating the water and creating a current in it, 
which seems to be appreciated by my anemones, and it may be of 
service to describe it. At one end of my aquarium, and just above 
high water mark, a hole has been drilled through the slate and a tin 
gas pipe cemented in; it is left projecting about one inch on the 
outside, and on the inside just sufficient to carry a length of glass 
tubing about the diameter of an ordinary quill; this is bent at 
several angles to enable it to lie safely along the sides and bottom 
of the tank, and at its extremity is bent, so that its end, drawn in a 
gas flame to a capillary point, projects into the middle of the water. 
To the metal tube on the outside of the aquarium a piece of elastic 
tube, attached to an india-rubber bellows is fixed, and by this means 
I am enabled to drive a stream of air into the water till it appears 
effervescing ; the fine bubbles from the spray remain in suspension 
for hours, and become ultimately absorbed. This apparatus, al- 
though not absolutely necessary, is attended by such good results, 
that I recommend its adoption; but a great deal of benefit arises 
from syringing the water with a glass syringe. And now for a few 
words on the third division of my subject—the occupants of the 
tank. Ifyou add nothing more to your aquarium than what will 
be found growing and multiplying as it were spontaneously, you 
will have abundant material for microscopical observation. I have 
been enabled in mine to watch the conjugation and multiplication of 
some of the Diatomacez, the development of the Foraminifera, the 
growth of the germs of the Marine Algz, the development of the 
Polyzoa, and the various transitional stages through which all these 
forms of marine life pass; these, and many other subjects of study, 
a successfully-established aquarium would afford, and if, after the 
example of Drs. Drysdale and Dallinger, these researches were re- 
corded, and every change faithfully drawn and preserved for future 
reference, abundant light would be thrown upon many obscure 
points in the developmental history of these objects. Every fact 
impartially obsérved and faithfully recorded, although per se but of 
small value, in the aggregate will prove that no more enticing path 
for the student of microscopic life can be offered than that which 
leads him through the comparatively untrodden and, therefore un- 
reaped fields of aquarium research. But I know that an apparently 
empty aquarium looks a joyless wilderness, and you will be anxious 
to see it tenanted by more visible objects of interest; and here let 
me give you a word of caution—Be content with still life. The 
student must be guided by his subject of study in stocking his tank. 
No harm will arise from putting in a few of the hardier varieties of 
the Actinide, some serpule or sabelle, and such like objects, bnt 
my experience is decidedly against over-crowding with anything; the 
atmospheric condition of your aquarium, if I may use the term, 
must not be abused any more than that of our own. We may now 
consider your aquarium in healthy working condition, and the 
