12 NOTES ON 
They move with great rapidity, both in 
running and swimming, and in the latter they 
are assisted by their tails. In rising, which they 
do occasionally for the purpose of respiration, 
they seem to beat the water, and sometimes 
hold their tail above its surface, to admit fresh 
portions of air into the trachee, by the stigmata 
or orifices near that part. In warm weather 
they creep up the stalks of plants, and remain 
near the’surface of the water, delighted to bask 
in the genial rays of the sun, while in cold 
weather they retire to the bottom, concealing 
themselves in the mud, where they remain in 
an almost torpid state. 
As they advance to their full size their mo- 
tions become sluggish, and if at this time they 
should be infested, as is very common, with the 
clustered Bell-polype (Vorticella convolaria)* 
these parasitical animalcules will rapidly in- 
crease in number, to the great annoyance of 
the larve. In a similar manner, when the 
larvee are kept in vessels too small to permit 
them to take sufficient exercise, the Bell-polype 
become so numerous as to occasion disease. 
As a microscopic object, however, these para- 
sites add materially to the interesting characters 
which it displays. Their appearance, to the 
* General History of Animalcules, figures 237 to 243. 
