Xi APPARATUS AND MATERIAL 
medium for making temporary mounts of most of the objects 
examined under the microscope. A solution made of equal parts 
of water and glycerine, however, is usually preferable to water, as 
it will not dry up and, besides, renders the object more transparent. 
None of the animals studied here need to be stained and mounted 
in balsam or other permanent medium. In the case, however, of 
the tapeworm, the hydroids, and perhaps one or two of the other 
forms, the animal can be studied with greater profit if thus stained 
and mounted, and it is recommended that the student be provided 
with such specimens. 
As a rule the material needed can be easily obtained. Most of 
the animals studied may be purchased from the supply department 
of the Marine Biological Laboratory at Woods Hole, Mass.; F. D. 
Lambert, Tufts College, Mass.; H. M. Stephens, Carlisle, Pa.; or 
other dealers in such supplies. Blackford’s, Fulton Market, New 
York City, will furnish the crayfish, the lobster, the edible crab, 
the French snail (Helix pomatia), and the squid. Powers & Powers, 
Station A, Lincoln, Neb., will furnish live protozoans and hydras. 
