PROTOZOA AXD SPONGES. 381 



whence it was about to be collected again. Hence it is 

 probably the first obscure rudiment of a circulation ; the 

 lluids impregnated with the products of digestion being 

 thus collected, and then diffused throughout the soft and 

 yielding tissues. 



The smaller bladder-like spaces that you see in con- 

 siderable numbers in the substance of the animal, are 

 collections of fluid contained in excavations of that sub- 

 stance, which are called vacuoles, differing from vesicles, 

 inasmuch as they seem to have no proper wall or inclosing 

 membrane, but to be merely casual separations of the 

 common substance, such as would be made by drops of 

 water in oil. These vacuoles appear to be connected 

 with the digestive function ; for very many of them are 

 not clear, but are occupied with granules more or less 

 opaque, and of exceedingly various dimensions. That 

 these collections of granules are food you will see by the 

 following experiment. 



I mingle a little carmine with the water, just enough to 

 impart a visible tinge to it, and close the live-box again. 

 Already you perceive that some of the tiny globules are 

 become turbid and red, and that their opacity and colour 

 are deepening perceptibly. We see by this that the par- 

 ticles of carmine have been taken into the jelly-like sar- 

 code, and are accumulating in little pellets surrounded 

 by fluids, in these casual hollows of its substance. The 

 process is rendered still more obvious when, as is often 

 the case, some Diatomacean,* with a hard siliceous shell, 

 becomes the food of the Amoeba. The apparently helpless 

 jelly spreads itself over the organism, so as soon to envelop 

 it; the flesh, which, having no skin, can unite with itself 

 whenever the parts come into contact, closes over the 



* The Diatomacece, a term formed from the Greek cia (dia), through, 

 and rkfivtiv (temneio), to cut, are so called from the ease with which 

 their masses may be broken or cut through ; whence their popular 

 name of brittle-worts. They are usually considered to belong to the 

 vegetable kingdom. 



