xii 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 require 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. 



The material needed for the study is usually easily obtained. 

 The marine forms and some of the others may be purchased in 

 quantities at reasonable rates of the following institutions : 



H. H. & C. S. Brimley, Raleigh, N.C., will furnish the large 

 southern grasshopper (Acridium americanum), the crayfish, the 

 earthworm, the freshwater mussel, and a large variety of other 

 animals. 



Blackford's, Fulton Market, New York City, will furnish the 

 crayfish, the lobster, the edible crab, the hard-shell clam, the Euro- 

 pean edible snail (Helix pomatia), the squid. 



Mr. George K. Cherrie, Bedford Park, 185 Brooklyn Avenue, 

 Brooklyn, N.Y., or the Supply Department of the Marine Biological 

 Laboratory at Woods Hole, Mass., will furnish any of the other 

 marine animals here studied. 



