186 THE AMERICAN MONTHLY [July, 



ous creatures and they are forced to swallow large quantities of 

 water. What becomes of it ? Is it regurgitated through the 

 pharyngeal passage and the oral aperture ? If it is, then it 

 passes up against a powerful ciliary current setting in in tlie 

 opposite direction. If there should be no way of disposing of 

 it, would not the ever-hungry creatures become dropsical to the 

 point of explosion ? The fact is that they never do. 



It is the generally accepted belief of microscopists that the 

 invisible channels ramifying throughout the endoplasm collect 

 this liquid and carry it, with any excretory products, to the 

 contractile vesicle whence it is expelled into the surrounding 

 water. It is not easy to color the contents of this contract- 

 ing organ, yet it has been done. It is no light task to demon- 

 strate that its contents hold uric acid in solution, yet that has 

 been done. Such experiments fail oftener than they succeed, 

 but they do succeed. I do not think that a gas could be stained. 

 The=e canals are supposed to be neither permanently fixed in 

 one position nor to have a special lining membrane, being, in 

 the latter respect, like the contractile vesicle itself. It is believed 

 that they open anywhere within the endoplasm, through which 

 they may not take the same course twice in succession; and 

 that the fresh water imbibed with the food, and that absorbed 

 through the body-surface, at some time surrounds every part- 

 icle of protoplasm in the organism, and gives to it its needed 

 oxygen, taking in exchange the useless excretory products and 

 carrying them to the contractile vesicle, whence they are ex- 

 pelled. If the protoplasm of the Infusoria is reticulated, as it 

 probably is and as that of Pelomyxa palustris and of the Amoeba 

 surely is, then these channels are not necessary to explain the 

 collecting of the liquid, for if the reticulated structure exists, 

 the circulation of the water amid the meshes of that living net- 

 work would be a beautiful contrivance, and would render super- 

 fluous the formation of water-canals anywhere except near the 

 contractile vesicle to lead the liquid into it. This is the ar- 

 rangement which I believe to be present, although it is not 

 possible to do anything whatever toward demonstrating it. Yet 

 it explains certain phenomeni readily observable, and other- 

 wise not readily accounted for. 



Uric acid crystals, or what amounts to the same thing, murex- 

 ide crystals, have been seen within the contractile vesicles of the 



