




1891.] Microscopy. 771 
MICROSCOPY.! 
The Nervous System of Convoluta.2—The discoverer of the. 
nervous system of the accelous Turbellaria, Yves Delage, recommends 
gold chloride as a means of demonstration. 
A number of Convoluta are placed in a watch-glass, and most of 
the sea-water removed. Formic acid (33 per cent.) is then poured 
over them, killing them almost instantly. At the end of two minutes 
the formic acid is removed, and gold chloride (one per cent.) put in 
its place. After ten or twelve minutes’ exposure the gold chloride is 
replaced. by formic acid (two per cent.), in which the Convoluta 
remain, in the dark, until the stain is complete (from one to three 
days). It is well to allow the planarians to become uniformly violet 
and opaque, and then to decolor them with cyanide of potassium (one- 
half per cent.). This reagent is allowed to act, according to the case, 
from two to twenty-four hours. The decoloring action can be arrested 
by washing with formic acid (two per cent.), The preparations can 
be mounted in balsam, but glycerine, with a slight admixture of 
formic acid, gives the best results. The prolonged action of the 
formic solution renders the animals supple, so that they are easily 
arranged on the slide. 
The results obtained with gold chloride are notoriously variable. 
According to Delage’s experience, out of three or four trials one at 
least is sure to be a success. In the same operation the results are 
different for different individuals. The best-stained specimens are 
easily recognized with a low magnifying power, and these alone are 
set aside for mounting. 
If sections are required, the worm, after being decolored in formic 
acid, must be hardened in the usual grades of alcohol. It is important 
to have the object extended and free as possible from wrinkles and 
contortions, This end can be best secured by subjecting the worms to 
slight pressure under a cover-glass while applying the formic acid (33 
per cent.).. Even then many of them will find space to twist them- 
selves out of shape, but some will remain straight, and these can be 
selected for cutting. 
In order to cut several individuals at once, all oriented alike, Delage 
passes them through chloroform, with a mixture of chloroform and 
paraffine. From this he removes them to a slide smeared with oil, and 
1 Edited by C.O. Whitman, Clark University, Worcester, Mass. 
2? Yves Delage. Arch. de Zool, Exp. et Gén, 1886, p. 113. 
