138 FAUNA AND FLORA OF NORFOLK : ROTIFERA. 
search with the 2 -inch objective gives one an idea of what 
is in the catch. 
When a suspicious individual appears in the field, the i-inch 
can easily be turned on, and if that does not allow of a positive 
determination of species, the individual is caught with a very 
fine pipette and transferred to a Rousselet compressor. 
The old-fashioned live box is an entirely useless contrivance 
compared with Mr. Rousselet’s neat invention. 
Under the gentle pressure of the micrometer screw of the 
compressor, the Rotifer is so nipped that she cannot move, 
yet not enough to injure her beauty. Then the 4-inch object 
lens is adjusted or preferably a highly magnifying eye -piece, 
inserted when the detail of jaws, antennae, etc., are made clear 
and the species can then be correctly determined. 
Should it be necessary to preserve the specimen, a very 
difficult operation follows. A weak solution of eucaine is 
added a drop at a time, and the animal is narcotised. As 
soon as she becomes placid and almost motionless, a drop 
of weak solution of osmic acid is then added and as quickly 
as possible removed again. Then frequent washings in 
foimalin, and finally a stronger solution of formalin is put 
with the animal on to a slide previously ringed with gum 
damar and shellac, dissolved in gold size. 
A careful adjustment of the cover slip is required to expel 
any bubble from the formalin and when the ring and cover 
is dry the slide can be stored as any other slide. 
I have had eight years’ continuous study of the Rotifers, 
and so most of them are now old acquaintances of mine, but 
one or two gave me a little trouble. These I sent off in a little 
tube of formalin to my great friend and coadjutor, F. R. 
Dixon Nuttall of Prescot, Lancs., who was able to identify 
all that he found, but did not find two species one of which 
I think is an entirely new species. Having, therefore, lost 
the only two specimens I pickled, I must hope to take it again 
at Sutton Broad. This has been almost my first attempt at 
the pickling process, and I therefore find it very difficult. 
Perhaps a high power positive microscope would help to- 
make it easier. 
