CHAPTER XXXVI. 529 



B. pyocyaneus . Excystation fairly rapid, growth 



good but amoebae encyst 

 rapidly. 



B. prodigiosus . . . \ 



B. megatherium . . . . Excystation fairly rapid, growth 



B. siibtilis . . . . j S od - 



B. proteus vulgaris . . . j Excystation fairly rapid, growth 



B. coli . . . . .1 poor, amoebae encyst very 



B. typhosus ... . . 1 soon. 



B. phlei . . . . . \ 



B. Eabinowitcli Excystation extremely slow, 



B. Ndbarro 3 



Pneumococcus 



growth very poor. 



Excyst fairly rapidly, growth 

 Meningococcus . . . ( slow, encystment very slow. 



Staphylococcus aureus . . Excyst fairly rapidly, growth 



fair. 



997. Collection.- -The great majority of the free living protozoa 

 are inhabitants of either fresh or salt water, and to obtain satis- 

 factory specimens some method of collection is essential. 



There are several pieces of apparatus which are more or less essential, 

 viz., a collecting stick with ring and net, collecting bottle and cutting 

 knife, a good pocket magnifier (about x 10), and small specimen 

 bottles. The collecting stick can be obtained from all opticians, and it 

 is usually fitted with the necessary appliances. The net is perhaps the 

 most essential part of the apparatus. It consists of a bag of soft mull 

 muslin fastened to a brass ring about 9 inches in diameter at one end, 

 whilst the other carries a rimmed glass bottle about 3 inches long by 

 1 inch wide. The cutting knife is a strong curved hook with a sharp 

 knife edge, which is screwed to the end of the stick, and is occasionally 

 useful for cutting pieces of water weeds, which would otherwise be out 

 of reach. A flat bottle, which can be obtained from most opticians, is 

 extremely useful for examining specimens secured by the net. In a 

 round bottle it is often extremely difficult to see minute organisms 

 clearly when examined with the magnifier, but with the flat bottle 

 one can usually quickly ascertain whether a sample is worth keeping 

 for study with the microscope. The magnifier should be a good one 

 and should be aplanatic. The most generally useful will be found to be 

 either Watson's aplanatic loops ; or one of Zeiss's hand lenses. The most 

 generally useful powers will be either the : 6 or 10, preferably both. 



The various forms of pond life can be divided, for collecting purposes, 

 into the free, and attached, and these groups will require different 

 treatment in the methods of collection. The free swimming forms are 

 often designated by the term " plankton," and these will be best ob- 

 tained by means of the net. In order to collect material with the net 

 it is passed through the water half a dozen times or so and then with- 

 drawn ; the pond water runs out, but the various infusoria, rotifera, etc., 

 are retained and are finally condensed in the bottle. They should 

 then be emptied either into the flat bottle for preliminary examination, 



M. 34 



