HYDRA. 



71. Living Animal. Carefully lift the Hydra on to a slide and examine it in water 

 under the low power without a cover-glass. Then put on a cover-glass, supporting it on 

 one side by a bit of paper in order to prevent it from crushing the Hydra, and examine 

 under the high power. Draw : body ; tentacles ; mouth ; also, if present, buds ; testis ; 

 ovary. 



72. Living Animal. Make a fresh preparation of the Hydra and examine with both 

 powers. Make drawing to show : ectoderm cells ; nematocysts with cnidocils ; endoderm 

 cells. 



Add 5 per cent NaCl and observe the discharge of filaments from the nematocysts. 

 Draw examples of isolated nematocysts. 



