USE OF INFUSORIA. 33 



well known, live and grow without any other ap- 

 parent means of sustenance. Thus the j resence of 

 Infusoria in the tank may be considered a sign of its 

 healthy condition, although their increase to such an 

 extent as to give a milky appearance to the water, 

 is apt to endanger the well-being of the larger, 

 though delicate creatures. The peculiar phenomenon 

 alluded to arises from decaying matter, such as a dead 

 worm or limpet, which should be sought after and 

 removed with all possible speed. The whereabouts 

 of such objectionable remains will be generally indi- 

 cated by a dense cloud of Infusoria hovering over the 

 spot. The milkiness, however, although it may look 

 for the time unsightly, is ofttimes the saving of the 

 aquarium ' stock/ When these tiny but industri- 

 ous scavengers have completed their task of purifica- 

 tion, they will cease to multiply, and mostly disap- 

 pear, leaving the water clear as crystal. I believe it 

 is the absence or deficient supply of Infusoria that 

 sometimes so tantalizingly defeats the attempts of 

 many persons to establish an aquarium. Pure deep- 

 sea water, although never without them, often con- 

 tains but very few, hence great caution is necessary 

 not to overstock the tank filled with it, otherwise the 

 animals will die rapidly, although the water itself 

 appears beautifully transparent. 



Of Infusoria there are many species. They are 

 nearly all, at one stage or other of their existence, 

 extremely vivacious in their movements; so much so, 



