216 APPENDIX. 



CHAPTER XII. (AMCEBA.) 



Amoeba is one of the most capricious of animals, appearing 

 and disappearing with inexplicable suddenness, and as a rule it 

 cannot be found at the time whenneedeo, unless special prepara- 

 tions have been made in advance. It is never safe to trust to 

 chance for a supply of material. It is equally unsafe to trust to 

 the methods usually prescribed. Amoebae may, however, often 

 be procured in abundance and with tolerable certainty as follows : 



is 



A month or six weeks beforehand collect considerable quantities 

 of water-plants (especially Nitella or Char a) from various pools 

 or slow ditches, with an abundance of sediment from the bottom. 

 It is important to select clear, quiet pools containing an abun- 

 dance of organic matter (such as desmids, diatoms, etc., in, the 

 sediment) not temporary rain-pools or such as are choked with 

 inorganic mud (dirt washed in by rain). The material thus pro- 

 cured should be distributed in numerous (10 to 20) open shallow 

 dishes (earthenware milk-pans) and allowed to stand about the 

 laboratory in various places some exposed to the sun, others in 

 the shade. The contents of many, perhaps all, of the vessels 

 will undergo putrefactive changes and swarm with life first with 

 bacteria, later with infusoria and will then gradually become 

 clear again as in a hay-infusion. The sediment should now be 

 examined at intervals, and Amoebcv are almost certain to appear, 

 sooner or later, in one or more of the vessels. Usually the small 

 A. radiosa appears first, but these should only be used if it is 

 f ound impossible to procure A. Proteus, which is far larger, clearer, 

 and more interesting. Experience will show that particular 

 pools always yield a crop of Amcebw, while others do not. 

 When once a productive source is found all trouble is ended. 



If possible a sediment should be selected that swarms with 

 Amoebw. It is very discouraging for students to pass most of 

 their time looking for the animals instead of at them. Large 

 cover-glasses should be used, and the material taken with a 

 pipette from the very surface of the sediment (not from its 

 deeper layers). "When first mounted the animals are usually con- 

 tracted, and only become fully extended after a time. Outline 

 sketches should be made at stated intervals, the structure of the 

 protoplasm carefully studied, the pulse of the contractile 



