&2 Rotifers. 
commence to work in a manner so like the pulsations of a heart 
that they were at one time mistaken for that organ. ‘They may 
be seen either swimming rapidly through the water by means of 
the vibratile cilia, called “wheels,” or crawling along the side of 
the glass, fastening to it by the head, and then curving the body 
until the tail is brought up to the spot, which is then fastened on 
to the glass and the head set free. They may also be seen 
fastened to a weed or the glass by the tail, the body waving to 
and fro, or thrusting itself straight out, and setting the wheels in 
active motion. 
One thing which has greatly contributed to the celebrity of 
these creatures is their powers of resuscitation. Leuwenhoek des- 
cribed the slow resuscitation of the animal when in a condition as 
dry as dust, directly moisture was brought to it ; and shortly after 
‘another eminent observer startled the world with the announce- 
ment that this drying and moistening could be repeated over a 
dozen times in succession, so that the Rotifer, whose natural term 
of life seldom exceeds eighteen days, could, according to this 
theory, be dried and kept for years and revived by moisture at 
any time. With regard to this last statement, there has been 
much difference of opinion ; but there is no doubt as to the fact 
that the Rotifer has a wonderful power of suspending animation, 
though the experiments that have been made would tend to show 
that, in order to ensure its resuscitation, it is a see gua non that it 
should be surrounded by a certain quantity of sand, so as to 
prevent the animal from becoming actually dried. Whenever it is 
completely separated from dirt and is veal/y dried, it perishes. 
Anyone who doubts the truth of this assertion can easily test it by 
placing some rotifers in a watch-glass without dirt and some in a 
watch-glass with dirt or moss, and allowing them to dry. They 
will find that the addition of a little water to the animals sur- 
rounded zwz¢h dirt or moss will cause them to revive; while those 
that were dried in the watch-glass zwzthout dirt will defy all efforts 
at resuscitation. ‘They may swell a little and elongate themselves, 
but they will not revive. A Rotifer once ¢horoughly dried is dead 
for ever. ‘The reason why Rotifers ever revive is because they 
have not lost by evaporation that small quantity of water which 
forms an integral constituent of their tissues, and it is the presence 
of the dirt and moss which prevents this complete evaporation. 
While on the subject of the extraordinary vitality of Rotifers, 
I will relate, for what it 1s worth, an anecdote that was told me 
lately. A gentleman who had invited some friends to come and 
see his collection accidentally left his bottle of Rotifers out in the 
garden, and as during the day there happened to be a somewhat 
severe frost, when he returned home in the evening he discovered 
the water containing his treasures frozen into a compact block of 
