MATERIAL FOR STUDY. 19 
The cyanide bottle described in Part F of Bulletin 
No. 39, U. S. National Museum, can be used instead 
of the tumbler if desired. Animals larger than insects 
may be killed by chloroform or ether. Earthworms 
should be killed in dilute alcohol. Starfish and sea- 
urchins are often killed by placing 
them in hot, but not boiling, water. 
Preserving Specimens in Alcohol. 
Part M of Bulletin No. 39 already 
mentioned gives valuable directions 
for the preservation of specimens. 
Alcohol is the most important pre- 5. og Tumbler 
serving fluid. For most specimens ~~ Vith "Chloroform. 
50% alcohol should be used at first. Drawn by A, E. 
This should be changed in a few “Sanford. 
days to a stronger solution, about 60%. If the speci- 
mens are to be permanently kept they should be 
transferred again to 70% alcohol. Strong alcohol as 
bought of the dealers is about 95% pure. This should 
be diluted some days before the specimens are put in 
it, to prevent the collecting of bubbles on the surface 
of the animals. Parts of animals for dissecting 
should be hardened gradually in alcohol. Hydras, 
hydroids, snails, mussels, and worms are best kept in 
alcohol. 
Preserving Specimens in Formalin. This liquid as 
usually bought is a solution of formaldehyde in water. 
For most purposes it should be diluted with water to 
make a 2% solution. Specimens to be used are kept 
in this fluid. 
Dried Specimens. For class use, butterflies may be 
kept in a tightly closed box containing naphthalin or 
camphor. Such specimens usually need to be preserved 
for a few months at most and can then be thrown away. 
Dragon-flies and other insects may be kept in the same 
box. Starfish may be dried by a slow heat after 
immersing for a time in hot water, not boiling, or after 
gradually hardening in alcohol. Sea-urchins may be 
