786 THE AMERICAN NATURALIST. [VoL. XXXIX. 
Worms to be kept alive for a considerable length of time! 
may be placed, immediately after collection, between folds of 
moist muslin in bacteria dishes, with not more than a dozen 
specimens in a dish. Change or wash the cloth occasionally — 
at least every two weeks. The worms may be fed on leaves, 
etc., if desired. With proper care, they will keep in this way 
for months, and are always clean and ready for use at a mo- 
ment's notice. The writer has found that the worms will keep 
quite as well if filter paper is used instead of muslin. | 
Preparation of Earthworms Jor Dissection.— Fresh specimens 
are too soft for convenient handling of the tissues during dissec- 
tion ; it is also inconvenient to keep a sufficient number of them 
alive for general dissection purposes ; hence preservation is 
resorted to. Two methods are available : — 
. (a) Chromic Acid Method. 
I. Killing— Place in 4% alcohol and gradually increase the 
strength to 8% in the course of the next two hours by adding 
Stronger alcohol a few drops at a time. Wash in water to free 
from mucus and again immerse in 8 % alcohol until the worms 
are thoroughly stupefied and no longer contract when pinched 
with forceps. 
2. Fixing.— Inject worms with 1 % chromic acid and immerse 
in the acid for about 4 hours. 
The injection. is best performed by means of a water pressure 
apparatus (see Fig. ı). This gives constant, uniform pressure. 
A head of about four feet of water should be used. A glass 
cannula may be made by drawing out the end of a piece of 1 inch 
glass tubing to a very fine bore, and breaking it so as to leave a 
sharp point with a raw edge. The exact size must be determined 
by experiment. The stream may be allowed to flow continuously 
from the cannula. A pipette with point drawn out fine may be 
used in case this apparatus is not available, but it is not very : 
satisfactory, 
1 i i | 
H. S. Jennings. « Keeping Earthworms Alive in Winter." Journ. of Ap- 
plied Micr., vol. 6, no. 7, PP- 2412-2413. 
