Earring and Myers—The Rotifers of Wisconsin . 651 
chlorate in 10 to 12 per cent, alcohol; the rotifers at once contract 
strongly, but expand again on recovering from the shock, swim 
feebly about, and soon sink to the bottom. The motion of the 
cilia should now be watched, and when it has nearly stopped, a 
BRASS WATCH-GLASS holder 
Text Figure 2 
drop of 1 per cent, osmic acid should be dropped on the animals 
and the water agitated for a moment, in order to distribute the 
acid through it. This kills and fixes at once; the animals should 
now be passed through several changes of water in order to re¬ 
move the osmic acid; if blackened, the material may be bleached 
in a weak solution of potassium hydroxide, stopping the action 
when the desired clearing has been attained. For nearly all the 
free-swimming forms this method gives very good results. 
The Rhizota are very sensitive to the cocaine solution; it should 
be added drop by drop to the water containing the animals; they 
will then be narcotized very slowly. 
Some Notommatids may be killed with auricles fully extended 
by “cooking”, which fixes the protoplasm with very little dis¬ 
coloration but swells the animals somewhat. The rotifers should 
be in a small quantity of water in a watch glass, just enough to 
allow them to swim about freely, and while they are in motion a 
considerable quantity of boiling water should be added suddenly. 
No satisfactory way has yet been found for narcotizing and 
killing the Bdelloids in an extended condition; but they have a 
tendency to die extended, and this tendency may be taken ad¬ 
vantage of by allowing them to die slowly in a large amount of 
water to which has been added a small quantity of narcotic, not 
enough to cause them to contract violently; fixing should be done 
as soon after death as possible. By this method fair results may 
be obtained with at least some species. 
All the loricate rotifers should be killed in 10 per cent, formalin 
without previous naerotizing, as the specific characters are more 
readily seen in contracted specimens. 
Preserved material should be kept in 2 per cent, formalin so¬ 
lution; formalin is here taken to mean the usual commercial so- 
