650 Wisconsin Academy of Sciences, Arts, and Letters . 
to avoid loss of material; the bottle should then be filled with clear 
water from the same source. Many species will be obtained in 
this way which are not to be had with the net. If the plants are 
not injured by being packed too tightly, and if the containers are 
kept in a subdued light, rotifers may be taken from them for days, 
as photosynthesis will be sufficiently active to keep up the oxygen 
supply and the absence of strong sunlight will retard the proces¬ 
ses of decay. Twenty-four hours after weed collections have been 
made, about one third of the water should be removed with a 
bulb pipette, keeping the opening as near the bottom as possible; 
an equal amount of fresh water should then be added. By doing 
this daily the collections may be kept for a week or more. 
When making weed collections it is a great convenience to have 
a metal hook, which can be screwed into the socket of the pole, 
replacing the net. A weighted, three-pronged grapple attached 
to a strong cord is desirable for collecting plants out of reach of 
the hook. Any kind of wide-mouthed bottle will answer for the 
field collections; a screw-top jar of 500 cubic centimeters’ capacity 
is very convenient. If several hours must elapse before the col¬ 
lections can be examined, thermos bottles are very good, as they 
keep the water at a constant temperature, and sudden changes are 
fatal to many rotifers. 
After reaching home the collections should be allowed to stand 
for some time in order to let everything settle. As the oxygen 
held in solution gradually decreases the rotifers work their way 
towards the surface, and will be found swimming or attached by 
the toes to the glass in the meniscus on the side toward the light; 
they can then be removed with a pipette. Nearly all the free- 
swimming species can be secured from the collections in this man¬ 
ner. The Rhizota must of course be searched for on the plants 
to which they are fixed. 
The rotifers are next transferred to watch glasses about 75 
millimeters in diameter. A convenient ring for holding these is 
made of a narrow circle of brass tubing with three holding clips 
soldered to the outside (text fig. 2). These rings keep the glasses 
from tilting and hold them securely so that they can be safely 
moved about on the stage of the dissecting microscope. 
After considerable experimenting, the following method of 
narcotization has been found to give the best results. To the 
water in the watch glasses containing the rotifers add at once at 
least an equal amount of a 5 per cent, solution of cocaine hydro- 
