52 MORPHOLOGY OF THE BACTERIA. 
This is not, however, exactly the opinion of 
Nageli, who seems to consider movement as the 
surest distinctive characteristic. 
“There are,’ he says, “but three distinctive 
signs which enable us to recognize with some 
certainty that granules under observation are or- 
ganisms, — spontaneous movement, multiplication, 
and equality of dimensions, united with regularity 
of form. 
“The most certain character is movement in 
a straight or curved line, —a movement which 
inorganic granules never present. One should 
take care not to be deceived by movements 
which are caused by currents in the liquid under 
observation. Nor should one allow himself to be 
deceived by the tremulous motion, called molecu- 
lar movement, in which the granules do not really 
change their position. These movements are seen 
in most cells, and even in those of the Schizomy- 
cetes, and inorganic bodies themselves present it. 
“ Multiplication is a character less important 
than movement. When among granules some 
are found united in pairs, it may be supposed 
with probability that division and multiplication 
are taking place. When rods are bent at an angle, 
one may predict their division in two parts. 
“ Finally, as to size and form. Granules of dif- 
ferent size and of a more or less irregular form 
ought not to be considered as belonging to the 
group of segmented fungi; if, on the contrary, 
the granules offer dimensions perfectly equal, and 
a spherical or oval form, the distinction is more 
