LABORATORY AQUARIUM. f 217 
hence most convenient for intensive work. Even when we 
have a good field for collecting, the aquarium is an indispen- 
sible adjunct to class work, and ever for research. Ecology 
and habits of plants and animals cannot be studied as well in 
the field as in the transparent jar. I will cite but a simple ex- 
ample. The omnivorous worm, Tubifex, is an inhabitant of 
pools periodically dry, and in sluggish streams it is often so 
abundant that the bottoms are colored red by the large num- 
ber. There has been considerable comment whether this worm, 
Tubifex, (so called because it builds a case or tube around it- 
self), has its anterior in the mud or out of it. These animals 
= constantly swaying back and forth in rhythmical motion, to 
ause water currents. They are often several inches long, 
dris the thickness of a read and the approach of any en- 
emy causing a disturbance in water near, is sufficient to make 
them retreat instantly into the ground and no trace of them 
is seen until quite is restored. Some will invariably dig down 
at the edge of the aquarium and their anatomy from one end 
to the other may thus be studied through rel glass with a 
magnifier, and without in the least disturbing them. Sound 
waves do not seem to effect them, though sound travels in 
water and when the vessel is struck a sharp resounding rap, 
they are not affected as some other small aquatic animals are. 
Some zoologists have maintained that these worms are ined: 
ded “head first" in the mud, others claim their heads or an- 
terior portion is ups and I am told that the ace Ns has 
not been settled. Now it does matter very much whether a 
worm wants to stand a "e head or otherwise, but it is very 
easy to settle the problem viewed in the aquarium, though in 
the field none seem to have been able to decide. A few moments 
observation will show to the veriest tyro that the food which 
these worms are continuously eating is seen passing upwards 
through their transparent bodies and finally cast out above, 
causing in part, the formation of the tube around them, from 
which they get their name. I have asked many students, some 
mere beginners, and all could solve the difficulty in a few sec- 
onds of observation. 
This is only one instance to show that if we wish to be- 
come better acquainted with the lower forms of life we must 
bring them near to us and study their ecology. The diffieul- 
ties of field study are such that little has been done heretofore 
with algae ecology. The aquarium for microscopic plants may 
in the future solve some of these problems, besides being a help 
and convenience for class work. 
