562 APPENDIX 



water ; parasites and Polytoma in the fluids in which they 

 live, diluted with a drop of normal salt solution. Para- 

 mecium may be made to move more slowly by the addition 

 of a little gum to the water in which it is mounted. 

 Polytoma is quiet in the drying edges of a film of the fluid 

 which contains it, mounted without coverslip. 

 2. Kill by placing at one side of the coverslip a drop of osmic 

 acid and drawing under with blotting-paper at the opposite 

 side, taking care not to sweep away the animals. Wash 

 with water in same way, stain in same way with picrocar- 

 mine, wash again, draw under coverslip glycerine, first 

 dilute and then pure. Flagella and trichocysts are best 

 shown by using iodine solution, which both kills and stains. 

 (Polytoma is best fixed with osmic vapour in a film on a 

 coverslip, stained there, and subsequently mounted.) 

 In living and stained specimens, note : shape, changing in Amceba 

 and Entamaba by amoeboid movement, in Euglena and Monocystis by 

 euglenoid movement ; pseudopodia, flagella, cilia, or absence of all these ; 

 nucleus (nuclei in Opalina) ; micronucleus in Ciliata except Opalina ; 

 staining of nuclei ; ectoplasm, endoplasm, food vacuoles (not in Hamato- 

 coccus, Polytoma, Euglena, Opalina, or Monocystis) ; contractile vacuole 

 or vacuoles (none in Monocystis), whether simple or complex ; tricho- 

 cysts in Paramecium ; red spot and chloroplasts in Euglena and 

 Hamatococcus ; gullet and vestibule in Ciliata other than Opalina ; 

 feed these Ciliata with Indian ink ground up in water ; stages of 

 Monocystis, as above. (Figs. 68-100, 391-393. ) 



Specimens of one or more species may usually be obtained by 



gathering weeds from a clean pond and allowing them 



Hydra. to stand in a vessel of water. Some of the Hydras will 



migrate to the wall of the vessel, where they can easily 



be detected, gently pushed off, and sucked up with a pipette. 



la. Note : extension, contraction on touching, spontaneous 



movements. 

 b. Place a brown specimen with a water-flea in a watch-glass 

 containing only a little water. Note that the water-flea is 

 numbed when it touches the tentacles of the Hydra. 

 Probably it will be seized and swallowed by the latter. 



2. With hand lens, note : body ; foot ; tentacles ; bud, testes, 



and ovary, if present (Figs, ioi, 106, and Plate XVI.). 



3. Mount in water, raising coverslip on two small strips of paper. 



Note ; with low power, oral cone and mouth ; with high 

 power, on tentacle, ectoderm, endoderm, batteries of 

 nematocysts, cnidocils (Fig. 403) ; after running 5 per cent, 

 salt solution under coverslip, threads of nematocysts 

 extruded (Fig. 104, D). 



Small animals often found running over the body of the 

 Hydra are ciliate Protozoa. 

 10. In stained and mounted sections (transverse and longitudinal), 

 note, under low power : ectoderm, endoderm, jelly, 

 enteron (Figs. 102, 103) ; under high power, details of 

 ectoderm and endoderm (Fig. 105). 



