No. 467.] ZOOLOGICAL MATERIAL. 787 
Fill a large shallow glass dish about à inch deep with 1 % 
chromic acid. (Cover the hands and wrists thickly with vaseline 
while working with chromic acid.) Take each worm separately 
and lay it in an extended condition in the chromic acid, keeping 
it straight and seeing that it is not twisted. Inject immediately, 





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Fic. r.— Constant pressure injection apparatus. a should be filled with water, part of 
which flows into 4; ¢ contains injection fluid, 
about 4 inch behind the clitellum, and again near the posterior 
end of the body if necessary. /mject into the body cavity; be 
careful not to pierce the alimentary canal. The worm should 
swell out slowly along its entire length and become very turgid. 
Too rapid injection may tear the tissues. 
The worms should be kept straight while in chromic acid. If 
left in the acid less than four hours they will eventually become 
too soft ; if left in the acid much more than four hours they will 
be too brittle. 
Wash thoroughly in running water until the yellow color is 
gone —about 12 hours. Be sure that the water reaches every 
part of the surface of each worm. If free acid remains on the 
worms it will make them brittle. The worms are a light drab, 
not yellowish brown, when well washed. 
