Burnett on Organic Relations of Infusoria, etc. 323 
genus Bodo (Ehr.) are the most interesting, from the fact of 
their having a long filamentous tail, which is their locomotive 
organ ; on this account, and because their form and presence 
are more constant than those of any other particles of this 
family, I have devoted considerable time to them. 
Those which are found in the intestines of the common 
house fly, or in those of the frog, answer very well for 
studies of this kind. Those in the fly, when first seen, 
resemble in shape a kernel of rye. They are about 44; of an 
inch in length, and ,3, in breadth. Attached to the body 
is a delicate hair-like tail, four or five times its length. By 
the addition of water the body becomes large by endos- 
mosis, assuming a perfectly spherical shape, after passing 
through all the intermediate ones, so that, when magnified 
with the highest power of Spenser’s microscope, it is nearly 
One inch in diameter; permitting the most thorough and 
satisfactory study of their structure, which I find, after re- 
peated observations, has no peculiarities except those belong- 
ing to cells. It isa closed cell-sac, with a filiform caudate 
process, and capable of the actions of cell-membranes, namely, 
endosmosis and exosmosis. In the interior of this sac are found 
sometimes a few granules, and sometimes a nucleus. In those 
of the frog, which are larger, I have seen distinctly in some a 
nucleus with a nucleolus, in others two nuclei, and in others - 
still, four nuclei of equal size; thus showing, that here the 
multiplication of cells, takes place as elsewhere, by seg- 
mentation of the nucleus. Aside from these characteristics, 
Which are sufficient, the fact that I have sometimes met with 
them in the interior of epithelial cells, would be strongly pre- 
sumptive of their cell-origin from minute granules that pass 
through the cell wall. The representatives of the genus Bodo, 
therefore, appear to be simple cells, each with a filiform ap- 
pendage for locomotion, and which locomotion, therefore, can - 
have no adaptive character. : 
There are differences in them, as they may be taken 
from different ocalities ; but because these particles are cells, — 1 
^ 
