18 
LIFE, IN ITS LOWER FORMS. 
stomachs at all, nor have they been able to discover any 
such common tube as the learned professor describes. 
The true explanation of the phenomena appears to be, 
that the gullet terminates by an open extremity in the 
midst of the gelatinous flesh that occupies the general 
cavity of the body ; and that the food, as swallowed, 
passes in pellets, enveloped in mucus, into this flesh, 
having assumed globular forms from the rotation pro- 
duced by the lining cilia of the gullet. These pellets are 
partly absorbed, and partly expelled by a proper orifice. 
There is another curious organ found in a large number 
of these animals, the office of which is even more puzzling. 
It is commonly known as the contractile bladder. If we 
are watching one of these animalcules, a Paramecium, for 
example, we see in a particular part of the body a circular 
space perfectly clear and colourless, which gradually en- 
larges until it takes the appearance of a distended globose 
bladder. When arrived at its utmost dimensions it sud- 
denly contracts to a point, and presently begins to enlarge, 
until it reaches its former size and appearance, when it 
again contracts as before. This alternation of distensions 
and contractions goes on continuously ; the latter taking 
place at regularly measured intervals, perhaps of about a 
minute. We feel assured, from numerous observations 
that the bladder is filled by some fluid which gradually 
percolates into it, and that this is discharged by the 
periodic contraction ; but what is the nature of this fluid 
and what relation the process sustains to the general 
economy, we are ignorant. Our own opinion is, that the 
organ, with its accessories, is the first rudimentary form 
of the urinary system of higher animals. 
