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, Lorn 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. 



