1929] 
Four New Forms of Eriophyes 
299 
method for manipulating small organisms. The mites are 
killed and cleared by heating them in a 10% solution of 
potassium hydroxide that is poured over them in the col- 
lecting vials after the plant tissues have been carefully 
removed. This solution containing the cleared mites is 
poured through a short piece of small glass tubing having 
at one end a guncotton plug in which the mites are caught 
as the solution passes through. The mites and the plug are 
then washed thoroughly with distilled water before the alco- 
hols of various grades are passed through the tube to 
dehydrate and harden the specimens. After treating with 
absolute alcohol the guncotton plug is removed together 
with the entangled specimens from the tube and placed in a 
vial containing a solution of absolute alcohol and ether in 
equal proportions by volume. In this solution the guncotton 
dissolves and the mites settle to the bottom of the resulting 
weak solution of celloidin thus formed. A drop or two of 
this solution and great numbers of the mites can be easily 
removed by a pipette to a slide smeared with albumen 
fixative ; the alcohol and ether evaporate rapidly leaving the 
mites embedded in a thin layer of celloidin. After reaching 
this stage the slides can be kept indefinitely before pro- 
ceeding or they can be colored immediately in acid fuchsin, 
dehydrated, and cleared in carbol-xylol before sealing on a 
cover glass with balsam or euparal. This method has two 
disadvantages that necessitate careful checking of the speci- 
mens thus mounted and those freshly mounted in other 
media. The first of these results from the destruction of the 
body contents by the use of potassium hydroxide solution, 
thus removing the most reliable indicator of the maturity 
of the females, that is, the content of eggs within their 
bodies. Since the classification is based primarily on the 
mature females it is important that only mature individuals 
should be used when making measurements for descriptive 
purposes. Secondly, there is a disadvantage in the position 
the specimens assume when mounted by this method; the 
setae and any slight curvature of the body become fixed 
during the hardening process and cause the specimens to 
roll upon their sides when transferred to the slides. The 
lateral aspect thus presented in these mounts makes it dif- 
