242 Transactions of the, Society. 



" An addition of new wheat should be made every one or two 

 months. There must be an abundance of nageUate, and ciliate 

 life in a thriving amoeba culture. This is supported by the 

 decomposing wheat which feeds the countless bacterial and other 

 lowly organisms requisite for its upkeep. 



" Other substitutes for wheat can be used successfully, e.g. 

 putrefying organic matter of any description provided it be 

 sufficiently diluted, but the wheat is easy to obtain, and the 

 quantities are easily gauged." 



These instructions would be useful similarly to anyone desirous 

 of making laboratory cultures, and who is in the position of having 

 discovered a good yielding source of amoebae, or who can obtain an 

 initial supply from a dealer. Ordinarily it is a much more lengthy 

 business to establish a luxuriant laboratory culture from natural 

 sources. Indeed the process may occupy a whole year, unless 

 particularly good habitats be discovered, and these are rare, for 

 although A. proteus is of almost universal occurrence, it is seldom 

 that the combination of circumstances necessary for the production 

 of a good supply is found in nature. Moreover there are great 

 fluctuations in the yield from well-favoured sources. 



Amoeba? are most likely to be found in places where a con- 

 tinuous supply of deca}'ing organic matter is being constantly 

 brought by the currents of water to a more or less sheltered place, 

 provided of course that this is not already over-run by animal 

 rivals of the amoeba. In addition to those enumerated below, fish 

 and frog tadpoles are inimical. 



A pond containing much organic debris, and not inhabited by 

 amoeba enemies, may sometimes yield a good supply — especially of 

 the diatom-eating strain [i.e. A. protcus (Penard 19U2), A. dubia 

 (Schaeffei-), A. jjroteus (X. Carter)]. 



In searching the gatherings the binocular microscope is useful. 

 From the beginning the would-be culturer should accustom himself 

 to surveying rapidly a large" quantity of material under the low 

 power, or under a mounted lens, over a dark background, when 

 the amoebae stand out as irregular whitish specks. Where they 

 are scarce they are likely to be overlooked if sought by means of 

 a higher magnification. The task of discovering the amcebse is 

 made easier if the material to be examined be placed under a 

 gently dripping tap for a week or more. The device of adding 

 wheat water to a prospective source and allowing the whole to 

 stand for some time is also helpful. 



Having then found some specimens the laboratory culture is 

 made by picking out the amceba? with a fine pipette, and putting 

 them into a test-tube containing one or two wheat grains, and the 

 necessary water. If the specimens are scarce they may be added 

 as they ^urn up. Other organisms are necessarily carried over in 

 this i^rocess ; the minute plants and filamentous algse oxygenate 



